Electric Vehicle Batteries
Electric vehicle batteries
Electric vehicles were commonly used from 1880 or so. Their increased use was limited by inefficent electric vehicle batteries. This also limited speed to only 35 km/h (22 mph). Their range was about 100 km (62 mph). It also awaited adequate control technology. (See also Electric Vehicle History)
Pic: Edison Battery Archives
From 1970 onward, technology improved dramatically. AGM batteries increased driving range slightly. Otherwise, electric vehicle batteries remained almost unchanged. Most provided about 33 watt-hours per kilogram.
Nickel Hydride
In 1991, the USA launched its Advanced Battery Consortium. This resulted in the nickel hydride (NiMH) battery. This initially doubled energy – to 68 Wh/kg. That has since doubled.
Early nickel hydride (NiMH) battery. Pic: ecomento.com
While having greater energy density, NiMH’s have low charging efficiency. Moreover, they are costly. Furthermore, they tend to self-discharge. There is also hydrogen loss. Nevertheless, they still power hybrid vehicles. Honda and Toyota use them. read more…
Electric Vehicle Home Charging
Charging your electric car at home or work
Electric vehicle home charging for small electric cars is feasible at home or at work from a 15 amp power point. A power cable plugs into the car’s on-board charger. Most such vehicles have a charging unit inbuilt.
Pic: https://cleantechnica.com/
Some electric car dealers include a home charging assessment price and/or a consultation with a licensed electrical contractor as part of the car’s purchase price.
A typical electric of hybrid used for typical commuting (of 40-50 km a day) uses 2.5-5.0 kilowatt/hours. This, often called one ‘unit’, usually costs less during off-peak periods .
This guide gives some indication of how many kilometres you can drive when charging typical electric cars from a home or similar supply at their maximum rate via that inbuilt charger.
| Type: | Maximum charge (kW) | km per hour of charging |
|---|---|---|
| BMW i3 | 7.4 | 25 |
| Chevy Spark EV | 3.3 | 11 |
| Fiat 500e | 6.6 | 22 |
| Ford Focus Electric | 6.6 | 22 |
| Kia Soul EV | 6.6 | 22 |
| Mercedes B-Class Elec. | 10 | 29 |
| Mitsubishi i-MieEV | 3.3 | 11 |
| Nissan Leaf | 3.3 – 6.6 | 11 – 22 |
| Smart Electric Drive | 3.3 | 11 |
| Tesla Models S & X | 10 – 20 | 29-58 |
Charging is readily done overnight but solar captured during the day can be sold to the electricity supplier.
All electric vehicle efficiency & emissions
All Electric Vehicle Efficiency & Emissions
This article, by Collyn Rivers, discusses electric vehicle efficiency and emissions. All road vehicles emit pollution (and are health issues). Emissions are in two main forms. One includes haze and particulate matter. The other are ‘greenhouse gases’, These include carbon dioxide and methane.
Vehicle pollution – 2019. Pic: Original source unknown
Particulate matter from tyres
Tyres constantly shed particulate matter. It is mainly soot and styrene-butadiene. The smaller particulates are airborne. They are a minor cancer risk. https://ncbi.nlm.nih.gov/pmc/articles/PMC1567725/.
The larger particles are washed into lakes and rivers etc. Related data, however, is scarce. Sweden, calculates tyre particulates as about 150 tonnes yearly. Battery-electric vehicles are heavier than those fossil-fuelled. Their tyre emissions accordingly increase.
Particulate matter from brake linings
Brake linings cause particulate emissions. These were initially asbestos cadmium, copper, lead, and zinc. All are now banned. They are now fibres of glass, steel and plastic. There are also antimony compounds, brass chips and iron filings. Also steel wool to conduct heat. These particulates disperse directly into the air. Their antimony (Sb) content may increase cancer. Most electric vehicles reduce speed by regenerative braking. This reduces brake lining emissions.
Regenerative braking
Many hybrid and most electric cars have regenerative braking. When needing to slow or stop your car’s drive motor acts as a generator. This charges the vehicle’s batteries.
Regenerative braking assists thermodynamic efficiency in all electric vehicles. Not just hybrids. It also reduces braking emissions.
Regenerative braking: whilst braking the drive motor acts as a generator, thereby charging the vehicle’s batteries. By doing so the vehicle’s kinetic energy is saved and stored for propulsive use. Pic: reworked from a concept of the Porter & Chester Institue, Connecticut, USA.
Tailpipe emissions
Electric vehicles produce negligable direct emissions. Hybrids produce no tailpipe emissions in electric mode. They have evaporative emissions, mainly during refueling. Their overall emissions are lower than those of 100% fossil-fuelled vehicles.
Indirect emissions from fossil-fuelled power stations
An Australian electricity power station. Pic: SMH.com.au.
Electric vehicles run from grid power must include power station emissions. Most of Australia’s power stations are fossil-fuelled. At an averaged 920 kg CO2-per megawatt/hour, ost are below average global efficiency. None rivals China’s 670–800 kg per megawatt/hour. India has many inefficient fossil-fuelled power stations, but is the world-leader of large-scale solar power. No fossil-fuelled power station, however, converts more than 40% of heat into electricity.
Some 78% per cent of the electricity generated by Australia’s power stations is from coal. Gas accounts for just under 10%. The remaining 12% or so is from hydro, wind and solar.
Due to Australia’s power stations emissions, it seems pointless to use an electric car powered via the grid network. When battery capacity permits, however, it makes sense to go all electric. This particularly if charged via solar. Or possibly via hydrogen fuel cells.
Future power stations
Australia is unlikely to build efficient fossil-fuelled power stations. Even reducing their existing pollution is enormously costly. Their output will inevitably be undercut by renewable energy. Wind plus solar and hydro systems are cheaper and simpler. Furthermore, (once apart from manufacturing and erecting) wind, solar and hydro is pollution free.
Quantifying petrol vehicle emissions
Oil-well to vehicle emissions must include extracting, refining and distributing. Furthermore, fossil fuel powered vehicle engines are about 25% or so efficient. The remaining 75% of the energy is lost.
Overall, every litre of burned petrol causes in 3.15 kg of CO2 emissions. About 81% is caused in burning the petrol, 13% by extraction and transportation, and around 6% from refining. Burning petrol’s released nitrous oxide has 300 times the global warming potential of CO2.
A typical fossil-fuelled Australian passenger car uses about 9.0 km/litre. Driving just one kilometre generates close to 350 grams of CO2 equivalent being emitted into the atmosphere. This is about 4.8 tonnes of CO2 equivalent emissions per car per year.
European disgrace
Some major European vehicle makers disgracefully concealed their diesel engine emissions. They included software that detected the vehicle’s emission were being checked. That software changed the engine’s operating mode accordingly to indicate reduced emissions.
Huge technical efforts have since been made to legimately limit fossil-fuel powered vehicle emissions. It is now, however, recognised it is not feasible to reduce them any further. This is particularly so of diesel. Reduced vehicle weight and performance assists but vehicle makers globally are now (2020) accepting their post-2030 products will be all-electric.
Current battery technology restricts range between charging. All-electric cars are fine for typical commuting to and from work. For general use right now however, hybrids make more sense.
Most cars are driven about 14,000 km/year. They emit about 4.8 tonne/year. The Toyota Prius hybrid averages just under 30 km/litre. It emits 31% CO2 (about 1.5 tonnes a year). That is 3.3 tonnes less than a comparable petrol-powered car.
Toyota Prius Hybrid. Pic: Toyota
Hydrogen
An increasing possibility is that hydrogen may replace oil as a global source of fuel. It can and is already being produced from fossil fuel. It can be done (and on a large scale) by passing an electric current through water. This now includes sea water. This enables it to be produced via both solar, wind-power and wave-power.
A so-called fuel cell enables hydrogen to be re-converted to electricity stored in so-called fuel cells. The fuel cell can then power an electric vehicle. This is not just conjecture. Many such vehicles now exist – mainly in California and Norway.
Australia’s main power stations – ages and emissions
Those known in terms of year built, and kilograms of CO2 per megawatt/hour (MWh) actually produced.
Stanwell (1996): 969 kg per MWh.
Bluewaters (2009): 982 kg per MWh.
Muja CD (1985): 982 kg per MWh.
Mt Piper (1996): 997 kg per MWh.
Collie (1999): 1004 kg per MWh.
Eraring (1982): 1011 kg per MWh.
Vales Point (1979): 1018 kg per MWh.
Callide B (1989): 1019 kg per MWh.
Bayswater (1986): 1031 kg per MWh.
Gladstone (1976): 1052 kg per MWh.
Lidell (1973): 1066 kg per MWh.
Muja AB (1969): 1285 kg per MWh.
Worsley (1982): 1324 kg per MWh.
A few of the above have now been (or soon will be) closed down.
The Electric Vehicle Series
This is a part of a series of articles about the history and technology involved in electric vehicles.
Electric Vehicle Motors
Electric vehicle motors
AC/DC
Electric vehicle motors use one or other of the two main kinds of electricity: alternating current and direct current. Both are effective as electric vehicle motors.
Alternating Current (AC) is where electric current constantly reverses its direction. It is that used in grid power supplies. In Australia and many other countries it cycles at 50 times a second. In America it cycles at 60 times a second.
Tesla Roadster AC motor. Pic: Tesla.
The AC induction motors used in a few electric vehicles have a stator (stationary coils of wire). When AC current flows through it, the stator generates a rotating magnetic field. That in turn causes a rotatable armature to revolve. It rotates at the rate of the AC current: i.e. at 50 or 60 times a second.
The relationship between AC voltage and its frequency enables changes in vehicle speed. The batteries’ DC output is converted to AC by an ‘inverter’. All that required is an inverter that has variable frequency. This is effective, but not that efficient.
AC induction motors are often used in hybrid vehicles. These use electric drive for limited commuting. Efficiency and range are not seen as major factors. There is however an increasing trend to direct current (DC) motors for electric vehicles.
Electric Vehicle Motors – Direct Current (DC)
Direct current (DC) is a flow of electrons in one direction. Edison is often credited as conceiving it. It was, however, initially conceived (in 1800) by Alessandro Volta. The term ‘Volt’ commorates his name.
A basic DC motor has fixed external magnets. These surround a revolving armature that is an electromagnet. It also doubles as the drive shaft. Direct current is fed to this electromagnet via a commutator.
Electric Vehicle Motors – commutators & brushes
The commutator is a basic DC motor’s weak point. It is a small ‘drum’ made of an electrically-insulating material. This drum has a number of copper segments. Carbon brushes, that conduct the DC current, are sprung against these segments.
The direct current is fed to the revolving armature via those brushes. This creates a magnetic field in the armature. The magnetic field causes the armature to spin through 180 degrees. A further mechanism causes the current fed to the brushes to reverse the DC’s polarity for the second 180 degrees. And so on.
While these motors work well, the carbon brushes sprung against rotating segments, wear out. They also constantly spark. This is a potential fire hazard. Moreover, it causes electrical ‘noise’ that must be suppressed.
A few electric vehicles use basic DC motors originally designed for other purposes. There are, however, many variants that combine the benefits of both AC and DC.
A DC electric motor’s commutator. One carbon brush is attached to the yellow lead. A second (out of sight) is on the left.
Brushless DC motors
A Brushless DC motor (BLDC), is in effect a DC motor turned inside out. It has permanent magnets on the rotor that generate a rotatable magnetic field on its outside. An electronic sensor monitors the angle of the rotor. Then, via high power transistors, it applies current to generate an external electromagnetic field. That field creates a turning force.
Brushless DC motor – Pic: original source unknown
Maximum torque at zero speed
Brushless DC motors develop maximum torque at zero speed. They are efficient electrically. Moreover, they have no brushes that wear out, and no need for internal cooling. Furthermore, this enables its internal bits and pieces to be free of contamination.
These motors produce far more torque than fossil-fuelled motors of comparable size and/or weight. They can rotate at far greater speed. They are relatively light and compact. Their available power is primarily limited by heat.
BLDC motors have minor downsides. They cost more to make than their brushed counterparts. Furthermore, d at present, the permanent magnets field strength is not adjustable. Work is in progress to make it so. Once achieved that will enable increasing maximum torque at low speeds when required. This is likely to be done by using neodymium (NdFeB) magnets.
Brushless DC motors cost more than most electric motors but are nevertheless proving commercially successful. They are used for Tesla’s Model 3. It seems likely they will dominate the market.
The Electric Vehicle Series
This is a part of a series of articles about the history and technology involved in electric vehicles.
Electric and Hybrid Vehicles
Electric Vehicle Batteries
Electric and Hybrid Vehicles
As of 2021, it is becoming increasingly clear that reducing fossil-fuelled vehicles (particularly diesel) to a truly safe level is impossible. Hence the trend to electric and hybrid vehicles. Many countries are already banning (or will ban soon) the sale of fossil-fuelled cars. These include France, Canada, Costa Rica, Denmark, Germany, Iceland, the Netherlands, Norway, Portugal, South Korea, Spain, Sweden, and the U.K. Twelve American states adhere to California’s Zero-Emission Vehicle (ZEV) Program.
The USA’s Trump administration eased the requirement. It reduced it from the mandated 5% a year – to 1.5% a year. Environmental bodies, led by California, challenged Trump’s backward step. Unless Trump is (improbably) re-elected, this situation is likely to change.
In the first year of the current regulation, carmakers must cut emissions by 10% more than Trump required. They would then have to make 5% yearly reductions.
Administration officials say the rule would save drivers money at the pump. It would decrease fuel consumption by about 200 billion gallons over four years. Furthermore, the standards would prevent an additional 2 billion metric tonnes of carbon pollution from being released into the atmosphere.
The proposal postpones ongoing arguments over how much to restrict vehicle emissions in 2027 and beyond. In the August 2021 executive order, the President directed agencies to begin work on the next standards.
John Bozzella, CEO of the Alliance for Automotive Innovation, called on Congress and state legislatures to invest in the infrastructure needed for the increase in electric and hybrid vehicles.
In a joint statement, Ford, General Motors, and Stellantis (the merger of Fiat Chrysler and French carmaker PSA) declared their ‘shared aspiration’ to make 40% to 50% of new vehicle sales electric by the end of the decade.
Environmental advocates cheered President Biden’s administration’s pledge to cancel the Trump regulations. Many, however, say the administration’s proposed replacement does not go far enough. In a letter to the President, they called for a 60% cut to vehicle emissions by 2030. This goal would be difficult to meet under the administration’s proposed pollution rules. Furthermore, environmentalists are wary of car companies’ ongoing promises to phase out internal combustion engines. ‘Today’s proposal relies on unenforceable voluntary commitments from unreliable carmakers to make up to 50% of their fleets electric by 2030’, says Dan Becker, director of the Center for Biological Diversity’s Safe Climate Transport Campaign. ‘Global warming is burning forests, roasting the West, and worsening storms. Now is not the time to propose weak standards and promise strong ones later,’ he said.
Becker and others said that auto companies already have the technology to meet tougher standards than those being proposed by the Biden administration, but rarely use it in the USA. Automakers argue they’re unable to meet stricter standards because Americans prefer larger, less fuel-efficient vehicles.
In recent years, some automakers have been able to meet federal standards. They do so, however, not by producing cleaner cars, but by cashing in credits earned by making a few electric and hybrid vehicles.
The proposed regulations are part of the administration’s efforts to push Americans to buy more electric and hybrid vehicles. Biden has asked Congress for hundreds of billions of dollars to make the vehicles more affordable through tax credits. Also to electrify 20% of the nation’s school buses by 2030.
At stake in that bill is the President’s ability to eliminate greenhouse gas emissions by 2050. Environmentalists say the only way to meet that goal is to mandate that all new cars be emissions-free by 2035.
So far the US federal government has announced its new rules to finalize fuel consumption and emissions standards; they’re in effect for the 2021–2026 model years. Fuel consumption and emissions must be reduced by 1.5 percent each year. The original proposal froze the standards at 2020 levels. California and other states continue to wage a lengthy legal battle to overturn all this.
Relaxed fuel-economy rules are now in effect. For new cars built over the next six years, automakers must still increase efficiency and lower carbon dioxide emissions each year but at a lower climb than the original regulations.
The new rules affect new cars and light-duty trucks from 2021 through 2026 model years. Fuel consumption and emissions must each drop by 1.5% annually as compared to the 2012 ruling’s 5% annual decreases. The 2018 draft proposal froze the 2020 model-year standards and applied them through 2026. The previous rule required an industry fleet-wide average of 54.5 mpg by the 2025 model year. This was later amended to 46.7 mpg. The final rule is 40.4 mpg. That rule ups the USA’s estimates of emissions and fuel consumption by up to two billion barrels and 923 million metric tons of CO2.
President Biden says the future of the auto industry ‘is electric and there’s no turning back. The question is whether we’ll lead or fall behind in the race for the future.’ His administration also unveiled a plan for new, stricter fuel economy and emission standards, which would be legally binding. Furthermore, they will be the most stringent such standards ever set – and followed by even stricter rules. Transportation is the USA’s largest source of greenhouse gases. Moving to electric and hybrid vehicles is seemingly the President’s central plank to fight climate change.
Ford, General Motors, and Stellantis, which make Jeep, Ram, and Chrysler vehicles, all issued statements expressing support for a 40% to 50% target of vehicle electrification. This is roughly in line with President Biden’s executive order. BMW, Honda, Volkswagen, and Volvo also said they supported it.
Currently, electric and hybrid vehicles account for about 2% of new car sales in the United States. A 40% to 50% target by 2030 is ambitious but the global auto industry has embraced electrification. Most automakers had already announced similar or more ambitious targets independently. Volvo, for instance, plans to be entirely electric by 2030.
‘These sales targets are certainly not unreasonable, and most likely achievable by 2030 given that automakers have already baked in large numbers of electric and hybrid vehicles into their future product cycles,’ noted Jessica Caldwell, an analyst at the USA car data site Edmunds. ‘Regardless of who has been in the White House, automotive industry leaders have seen the writing on the wall for some time now when it comes to electrification’.
Pic: www.drivespark.com
Apart from minor rubber tyre particles, electric vehicles are virtually emission-free. They are also about 80% efficient. If, however, their electricity is from fossil-fuelled power stations, their emissions are similar to year-2020 petrol-fuelled (or hybrid) vehicles.
Dirty Power Stations
Electricity vendors promote grid energy as ‘clean’. At present, however, that applies only to its usage. Worldwide, its generation is mostly filthy. In many countries, they generate about one–third of all carbon monoxide emissions.
Fully electrically-powered vehicles are virtually non-polluting. Most are over 80% energy efficient. If, however, the electricity they use is from most current power stations, their emissions are no lower than of a 2021 model petrol or hybrid vehicle. It thus makes little environmental sense to use an electric-only vehicle unless that electricity is wind or solar-generated. In many parts of the world is feasible (for commuting at least) to charge an electric vehicle by using solar energy at your home or place of work.
Electric and hybrid vehicles – the energy required
Most electric cars use about 1.0 kW/h to travel about 5 km. An electric vehicle (used as above) thus uses about 8 kWh of electricity/day. Grid electricity, on long-term contracts, costs about 20 cents per kW/h. If so the fuel cost is a mere A$1.60 daily. However, using grid power results in no overall fall in emissions. Unless you can solar-generate about 8 kW/h for daily commuting, it is better to use a hybrid as a typical hybrid generates less pollution than an electric-only vehicle run from our existing power stations. Hybrids, however, are being progressively being phased out globally.
Charging from home solar
For those with ample home or business solar, it is readily feasible to charge the battery (or fuel cells) from that source. Such charging can even be done overnight by selling daytime solar energy to a grid supplier. You then repurchase it (often at low off-peak rates) at night. Or, to have ample solar energy available where the vehicle is parked during the day. Where ample sun access is available, there is a business opportunity for parking stations to provide vehicle battery charging.
Battery Technology
Mainly retarding electric-car development is the ultra-slow improvement of rechargeable batteries. The first-known lead-acid was invented by Gaston Planté (in 1859). In 1881, Camille Alphonse Faure’s improved version (of a lead grid lattice and a lead oxide paste) enabled higher and flexible performance. It was also easier to mass-produce. Sealed versions later enabled batteries to be used in different positions without failure or leakage. That apart, there were no significant developments until the AGM (Amalgamated Glass Matt) version initially developed for the U.S. military around 1980.
The next major development was the lithium-ion battery. This reduced battery weight and volume by over three times. It enabled charging and discharging at far higher rates. But while a significant battery breakthrough, its energy storage of 0.5 MJ per kilogram is tiny. That of petrol and diesel’s is 45 M.J. per kilogram: that of hydrogen’s is 142 MJ per kilogram.
The latest major development (late-2020) is graphene-based batteries. These can (potentially) provide up to 750-800 km per full charge. Graphene is a one-atom-thick composition of carbon atoms. The atoms are tightly bound in a hexagonal or honeycomb-like structure. This virtually two-dimensional structure enables excellent electrical and thermal conductivity. It also provides high flexibility and strength, and low weight.
Graphenano claims its graphene-based batteries can be fully charged in just a few minutes. Furthermore, that they can charge and discharge 33 times faster than lithium-ion. Another development, (Gelion), uses zinc-bromine chemistry in combination with advanced electrolytes. These can be all-liquid, liquid/ion gel, or all-ion/gel.
Solid-state Batteries
Samsung’s Advanced Institute of Technology’s (SAIT) revolutionary solid-state battery may provide up to 1400 km (875 miles) range. They are about half the size of comparable batteries. The first commercial vehicles with such solid-state batteries are likely to be launched by 2025 or so.
SAIT is also studying lithium-air battery technology. It focuses on cathode technology, protective films for lithium metal anodes, and electrolytes for energy-density improvement, long-term reliability, and safety. This technology has the potential to provide a range of more than 800 km (500 miles) on a single charge.
Battery Prices
Battery prices, which were above $1,100 per kilowatt-hour in 2010, fell to $156 per kilowatt-hour in 2019. Research company BloombergNEF forecast that the average price will be close to $100/kWh by 2023.
Many other battery technologies are in hand – as are significant developments in fuel cells.
Hydrogen as a fuel
Worldwide, hydrogen is being seriously considered to replace petroleum products. A major benefit is that it is close to being emission-free. A downside, however, is that is very corrosive. In terms of mass, hydrogen has nearly three times the energy content of petrol: 120 MJ/kg versus 44 MJ/kg for petrol. In terms of volume, however, liquified hydrogen’s density is 8 MJ/L. Petrol’s density is 32 MJ/L.
Work is in progress to highly compress stored gas. Fibre-reinforced composite pressure vessels are capable of withstanding about 700 times the atmospheric pressure at a lower cost than before. Other ways include cold or cryo-compressed hydrogen storage, and materials-based hydrogen storage technologies. These include sorbents, chemical hydrogen storage materials, and metal hydrides.
Hydrogen can be used to power existing petrol-powered vehicles (and with only minor changes). Plans have already been drawn up to have fleets of hydrogen fuel-cell electric buses on routes in up to ten central hub locations across Australia.
Another approach (already by car makers) is electric vehicles fuelled by stored hydrogen that is converted to electricity by a fuel cell.
Hydrogen fuelling stations
According to the U.S. Department of Energy (DOE) the major hydrogen-producing states are California, Louisiana, and Texas. ‘Today, almost all of the hydrogen produced in the United States is used for refining petroleum, treating metals, producing fertilizer, and processing foods,’ the department states. However, in California, a new market for hydrogen is opening up, one driven by the demand for the gas to power fuel-cell electric vehicles. The state has been actively encouraging the growth of this market, offering carbon credits which act as an incentive to providers of hydrogen and other clean-energy technologies to establish and grow out their businesses in California.
In addition, last September, California Governor Gavin Newsom signed an executive order requiring that by 2035, all new cars and passenger trucks sold in California be zero-emission. A number of international truck manufacturing companies have already announced plans to introduce hydrogen fuel-cell powered long-haul trucks, while passenger cars fueled by hydrogen, such as the Toyota Mirai, are already on the market.
Of the 48 hydrogen fueling stations in the U.S., 45 are located in California, according to the DOE. In total, California has 50 laws and incentives related to the use of hydrogen, compared with Texas, which has seven.
Fuel cells
Fuel cell electric vehicles are fuelled by stored hydrogen that is converted to electricity by the fuel cell. They are more efficient than conventional internal combustion engine vehicles. They are almost silent. Furthermore, they produce no harmful emissions: only very pure water vapour and warm air.
These vehicles and the infrastructure to fuel them are in the early stages of being implemented. As with conventional vehicles, they take under five minutes to refuel. Currently, most have a range of about 500 km (300 miles). Fuel cell electric vehicles also have regenerative braking systems. These capture the energy lost during braking and store it in a battery.
Higher Weight – a Benefit for Towing
Lighter and more energy-compact batteries are evolving. Without a truly major change in battery technology, however, vehicles suitable for travel trailer towing are likely to be heavier than now (late 2021). This weight, however, is a bonus. For towing stability, the tow vehicle needs to outweigh the travel trailer.
The secondary source of electrical energy for RV and domestic use may well be via fuel cells, of which there is significant and ongoing international development.
Electric motor drive is ideal for travel trailer towing
Fossil-fuelled vehicle engines only develop their maximum torque (i.e. turning power) at relatively high engine speed. The types of electric motor used in electric and hybrid vehicles, however, develop maximum torque at zero and low speed. This characteristic is ideal for travel trailer towing.
Electrical and hybrid vehicles suitable for travel trailer towing
Many hybrid SUVs and serious off-road 4WDs are available in Australia. These include the Land Rover and Range Rover, Lexus NX and R.X, the Mercedes GLE, the Mitsubishi Outlander, Nissan Pathfinder, Porsche Cayenne and Volvo X160 and X190. Also possibly worth considering are the Rivian XIT and RIS. Scheduled now for sale in 2022, each has four electric motors totalling 550 kW of power (750 hp) and 1124 Nm of torque. These enable a claimed 0-100 km/h sprint in around three seconds, with a claimed range of over 640 km (400 miles). Why anyone needs such power, however, is unclear. One U.S. magazine suggests the Rivian ‘looks like a Ford F-150 on a gym-and-yoga regime’.
Both the R1T and R1S are underpinned by the same all-electric ‘skateboard’ platform, offering up to 644 km from a 180 kWh battery pack for the dual-cab ute, and 483 km from a single charge for the seven-seat SUV.
The Toyota Land Cruiser is already being converted to an all-electric drive (for mining applications) by the Dutch company Tembo.
The Tembo Electric LandCruiser. Pic: Tembo.
According to Japan’s Best Car Web a local company is also planning to sell electric-only LandCruisers for normal use. Toyota may offer a petrol/electric hybrid Land Cruiser in Australia. The company launched one in the USA. Sales, however, did not exceed 8000 or so. The iconic Jeep Wrangler is to be sold in a hybrid form – probably by 2022. Full details have not yet been released.
The prospects for RVers are generally good. There are seemingly no downsides apart (and initially) a need to ensure charging facilities are available in remote areas. That, however, is cheaper and simpler than for petrol or diesel. It also offers opportunities for landowners to build solar arrays and install rapid chargers
Feasible from solar
For those with ample home or business solar, it is readily feasible to charge the battery (or fuel cells) from solar. Such charging of electric and hybrid vehicles can even be done overnight by selling daytime solar energy to a grid supplier and repurchasing it (often at low agreed-off-peak rates) at night. Or, to have ample solar energy where the car is during the day.
Electric vehicle charging
The cable, usually supplied with the vehicle, plugs into a 10-15 amp, single-phase power point. This, however, will provide only 10-15 km of range per hour that you’re plugged in. Not recommended if you want to fully charge your vehicle in a hurry.
That which is really required is a commonly called ‘fast charger. This needs from 25 kW to 35 kW (40–50 amp, three-phase). These are typically found in commercial premises, car parks and a few road-side locations. If at home, consult an electrician to see if it is feasible. It generally is, but will need specialised installation.
Once plugged in, the home installation will provide about 150 km of range per hour plugged in; the upper end can give you a full recharge in as little as 10 to 15 minutes.
A public AC charging point at a shopping centre or car park and a standard domestic AC “wall box” charger (which can be powered by renewable energy, like solar) you’d have at home are capable of charging at a rate of up to 7 kW (10-15 amp, single-phase). You can expect to gain around 40 km of range per hour plugged in, which will most likely be enough to top up your average daily use, and capable of fully charging your electric vehicle overnight.
How many electric car charging stations are there in Australia? At this stage, there’s not a whole lot spread across the map: approximately 2500, which is a drop in the ocean when you consider that China has 800,000-plus public EV chargers, having rolled out a whopping 4000 a day in December 2020 alone.
There are several EV charging infrastructure providers operating within Australia, including Chargefox (currently our biggest network), Jet Charge, Tritium, EVSE, Schneider Electric, Keba, EVERTY, NHP Electrical Engineering and eGo Dock.
In terms of where are the chargers within Australia, here’s a brief breakdown based on statistics gathered in October 2020.
NSW
153 DC chargers and 630 AC chargers for a combined total of 783 charging points (as you’d expect, the majority of these are in and around Sydney). There are approximately 4627 EVs in NSW, meaning there are only 0.17 charging stations per EV.
Victoria
86 DC chargers and 450 AC chargers for a combined total of 536 charging points. According to EV charging network provider Chargefox, an EV charging station located in the inner Melbourne suburb of Brunswick is the country’s busiest, with 725 charging sessions alone for the month of March, 2021.
QLD
Has 59 DC chargers and 336 AC chargers for a combined total of 395 charging points. Queensland also has what they call an “electric super highway” consisting of 31 fast-charging sites, allowing Queenslanders and tourists to confidently travel from Coolangatta to Port Douglas, and from Brisbane to Toowoomba in EVs.
WA
Has 25 DC chargers and 202 AC chargers for a combined total of 227 charging points. In April 2021, motoring organisation RAC Western Australia opened Perth’s first ultra-rapid charging station at its head office in West Perth, with chargers available offering 400km of range in less than 15 minutes.
SA
19 DC chargers and 216 AC chargers for a combined total of 235 charging points.
NT
Zero DC chargers and 13 AC chargers for a combined total of 13 charging points. No, that’s not a lot.
ACT
11 DC chargers and 39 AC chargers for a combined total of 50 charging points.
Tasmania
4 DC chargers and 64 AC chargers for a combined total of 68 charging points.
The future of EV charging stations in Australia
The adoption of EVs in Australia has been slow, hence a relatively low number of public EV charging stations, but the situation is improving.
There’s been an increase in federal and state governments investing in public chargers, and private companies have been building networks along highways.
Local councils are also increasingly installing chargers in public areas as demand for EV chargers from local communities increases.
In the Australian government’s Infrastructure Priority List 2022-23 (a guide to the investments required to ‘secure a sustainable and prosperous future’) – the independent advisory body (Infrastructure Australia) identified the development of a fast-charging network for electric cars as one of Australia’s highest national priorities over the next five years. Infrastructure Australia, however, cited a lack of access to charging stations as a major hindrance to the uptake of electric cars.
Furthermore, data from the Electric Vehicle Council of Australia (EVC) states that Australia currently has less than 2000 public charging stations and only 250 of those are fast-charging stations. The EVC likewise cites the lack of charging stations in Australia as hindering the uptake of electric and hybrid vehicles. Moreover, data shows that two-thirds of drivers still regard the lack of sufficient charging stations as a major barrier to buying an electric vehicle.
(Those currently existing in late 2020 are listed at https://myelectriccar.com.au/charge-stations-in-australia/red)
But what exactly is an electric car charging station? And are there electric car charging stations in Australia?
Different types of electric car recharge station
When it comes to categorising EV chargers, there are three different levels.
The bog-standard wall socket you plug your toaster and mobile phone charger into that delivers AC electricity? That’s a Level 1 charger.
A cable usually supplied with the EV plugs into the 10-15 amp, single-phase power point, delivering around 10-20 km of range for each hour that you’re plugged in. Not recommended if you want to fully charge your EV in a hurry.
Level 2
A public AC charging point at a shopping centre or car park and a standard domestic AC “wall box” charger (which can be powered by renewable energy, like solar) you’d have at home are both Level 2, and these dedicated EV chargers are capable of charging at a rate of up to 7 kW (10-15 amp, single-phase).
Expect to gain around 40 km of range per hour plugged in, which will most likely be enough to top up your average daily use, and capable of fully charging your EV overnight.
Level 3
Commonly called “fast chargers” or “superchargers”, these are dedicated DC chargers that operate at power levels from 25 kW to 350 kW (40–500 amp, three-phase).
As you’d guess, DC chargers deliver electricity a whole lot faster than AC chargers, and they are typically found in commercial premises, car parks, and roadside locations.
Once plugged in, the lower end of this method will add about 150 km of range per hour plugged in; the upper end can give you a full recharge in as little as 10 to 15 minutes.
Tesla has its own network of DC Superchargers in Australia – there are close to 40 spread around the country, with more on the way – but despite being the world’s fastest chargers, they’ll only work with Teslas and no other EV models.
Electric car charging stations in Australia
As of late 2021, Australia has less than 2500 public car charging stations. proximately 2500, which is a drop in the ocean when you consider that China has 800,000-plus public EV chargers, having rolled out a whopping 4000 a day in December 2020 alone.
There are several EV charging infrastructure providers operating within Australia, including Chargefox (currently our biggest network), Jet Charge, Tritium, EVSE, Schneider Electric, Keba, EVERTY, NHP Electrical Engineering and eGo Dock.
In terms of where are the chargers within Australia, here’s a brief breakdown based on statistics gathered in later 2020.
NSW
153 DC chargers and 630 AC chargers for a combined total of 783 charging points (as you’d expect, the majority of these are in and around Sydney). There are approximately 4627 EVs in NSW, meaning there are only 0.17 charging stations per EV.
Victoria
86 DC chargers and 450 AC chargers for a combined total of 536 charging points. According to EV charging network provider Chargefox, an EV charging station located in the inner Melbourne suburb of Brunswick is the country’s busiest, with 725 charging sessions alone for the month of March, 2021.
QLD
Has 59 DC chargers and 336 AC chargers for a combined total of 395 charging points. Queensland also has what they call an “electric super highway” consisting of 31 fast-charging sites, allowing Queenslanders and tourists to confidently travel from Coolangatta to Port Douglas, and from Brisbane to Toowoomba in EVs.
WA
Has 25 DC chargers and 202 AC chargers for a combined total of 227 charging points. In April 2021, motoring organisation RAC Western Australia opened Perth’s first ultra-rapid charging station at its head office in West Perth, with chargers available offering 400km of range in less than 15 minutes.
SA
19 DC chargers and 216 AC chargers for a combined total of 235 charging points.
NT
Zero DC chargers and 13 AC chargers for a combined total of 13 charging points. No, that’s not a lot.
ACT
11 DC chargers and 39 AC chargers for a combined total of 50 charging points.
Tasmania
4 DC chargers and 64 AC chargers for a combined total of 68 charging points.
The future of EV charging stations in Australia
The adoption of EVs in Australia has been slow, hence a relatively low number of public EV charging stations, but the situation is improving.
There’s been an increase in federal and state governments investing in public chargers, and private companies have been building networks along highways.
Local councils are also increasingly installing chargers in public areas as demand for EV chargers from local communities increases.
Infrastructure Australia has called for the Australian government to, over the next five years, ‘develop a network of fast-charging stations on, or in proximity to, the national highway network to provide national connectivity’: and ‘developing policies and regulation to support charging technology adoption’.
Read more about electric cars
Electric Hybrid Vehicles
Electric hybrid vehicle
Electric hybrid vehicles are powered by either or both electricity and fossil fuel. They are far from new. In 1898, Ferdinand Porsche developed a hybrid car (the Lohner-Porsche). Its petrol engine ran a generator powering electric motors in its front wheels. The car had a range of 60 km (about 37 miles) from batteries alone.
The 1898 Lohner-Porsche- the first hybrid car. Pic: Original source not known.
In 1905, American H. Piper applied for a patent for a petrol-electric hybrid vehicle. It was claimed to reach 40 km/h (25 mph) in ten seconds. The patent took a long time before granting. By the time it was, petrol-fuelled vehicles achieved similar performance.
Woods Motor Company Dual Power
The best-known early hybrid is the Woods Dual Power Model 44 Coupe. It was made from 1917-1918. The vehicle had four-cylinder 10.5 kW petrol engine. This coupled to an electric motor. The motor was powered by 115 Ah lead-acid batteries. Below 24 km/h (15 mph) the car ran from electricity. Above that, the petrol engine took over. Maximum speed was about 55 km/h (34 mph). Much like today’s hybrid cars, it had regenerative braking. Reversing was by causing the electric motor to run backwards.
The Woods petrol-electric hybrid. Pic: courtesy of Petersen Automotive Museum Archives
The Woods car was promoted as having unlimited mileage, adequate speed and great economy. Also that it was faster than most electric cars. It was very costly. Only a few hundred were sold.
The first era of electric cars was ending. Whilst quieter, none could compete with Ford’s petrol Model T. Furthermore, battery development was static. Moreover, there was thus little incentive to develop electric motive power.
Hybrid revival
Hybrid development re-arose in the USA and Japan. Due to increasing air pollution, in 1966 the U.S. Congress recommended electric-powered vehicles. One (in 1969) was General Motors’ experimental hybrid. It used electric power to 16 km/h (10 mph). It then used electric and petrol power until 21 km/h (about 13 mph). From thereon it ran on petrol. Its maximum speed was about 65 km/h (about 40 mph).
The Arab oil embargo (1973) increased interest in electric powered vehicles. One result was Volkswagen’s experimental petrol/ battery hybrid. It was not, however, mass-produced. Another was the US Postal Service trialled battery-powered vans.
In 1976, the USA encouraged developing hybrid-electric components. Furthermore,Toyota built its first (experimental) hybrid. It used a gas-turbine generator to power an electric motor.
In 1980, lawn-mower maker Briggs and Stratton developed a hybrid car. It was driven by a twin cylinder 6 kW engine. It ran on ethanol, an electric motor, or both. Twin rear wheels bore 500 kg of batteries. It could travel 50 to 110 km (31-70 miles) in electric mode, and about 320 km in hybrid. The car was a promotion for the maker’s lawn-mowers. To put it mildly, its adverse power/weight limited performance. Its reported time to reach 80 km/h (50 mph) in combined mode was 35 seconds. By comparison, even today’s slowest cars need only a few seconds.
The Briggs and Stratton hybrid. Impressive visually –but seriously underpowered.
A battery boost
A major boost for hybrid vehicles was the USA’s (1991) ‘Advanced Battery Consortium’. It aimed at producing a compact battery. The US$90 million cost resulted in nickel hydride batteries. These had about three times the capacity of comparable lead-acid batteries. This was still less than needed. It did, however, enable a new generation of electric vehicles. Hybrid and otherwise.
Toyota’s ‘Earth Charter’
In 1992 Toyota outlined its ‘Earth Charter’. Its intention was to develop and market vehicles with minimal emissions. Also that year, the USA sought low emission cars. The aim was fuel usage under 3.0 litres/100 km. Three prototypes (all hybrids) resulted. For likely political reasons, Toyota was formally excluded.
That decision back-fired. It prompted Toyota to create the Prius. That car initially went on sale, in Japan, in December 1997.
The original (1997) model NHW10 Toyota Prius. This initial model was sold only in Japan. Some, however, were imported privately into many countries. Pic: Original source unknown.
The initial version’s petrol engine produced 43 kW. Its electric motor produced 29.4 kW. It was powered by nickel-metal hydride batteries. Torque (at zero rpm) was 305 Nm. Later models had a larger petrol engine. It produced 53 kW and 115 Nm torque.
The car was an instant success. Some buyers waited six months for delivery. The Toyota Prius was launched in Australia in 2001.
European hybrids
In 1997, Audi mass-produced a hybrid. It was powered by a 67 kW 1.9-litre turbo-diesel engine. It also had a 21.6 kW electric motor. This was powered by a lead-acid gel battery. The car, however, failed to attract buyers.
Audi’s experience caused Europe to concentrate on reducing diesel emissions. Doing so, however, had ‘limitations’. Because their emissions fell far short of EU requirements, some makers illegally disguised the true levels.
Meanwhile, most electric and hybrid development was in the USA and Asia. Progress in Europe was initially slow. Now, however, (2020) there are many European electric and hybrids.
Owned by BMW, the first Mini hybrid had a 1.5-litre three-cylinder petrol turbo engine. Its electric motor had 65 kW of power and 165Nm of torque. It was powered by a 7.6kWh lithium battery. BMW claims it can travel to 40 km (about 25 miles) on electric power. A later version has a claimed 47 km (29.3 miles) range. Fuel economy is claimed to be 2.1 litres/100km. CO2 emissions are claimed to be 49 g/km.
Mini hybrid –the Countryman S E ALL4. Pic: https://www.mini.co.uk
BMW’s own hybrid initially used a 0.65 litre petrol engine to charge the drive battery (if needed). The car has since been replaced by an all-electric version. The 42.2 kWh battery enables a claimed range of 310 km (194 miles).
Porsche has two hybrids. The 2019 Cayenne E-Hybrid has a 3-litre turbocharged petrol engine. It is claimed to produce 250 kW and 450 Nm torque. An electric motor adds an additional 100 kW. Plus 400 Nm torque.
The Porsche Panamera 4 (hybrid) is much as the Cayenne hybrid. Its Turbo S E-Hybrid has a twin-turbo 4.0-litre V8 petrol engine. It develops over 505 kW and 850 Nm. Its claimed all-electric range is 22.5 km (14 miles). Furthermore, it is claimed to use 4.9-litre of petrol per 100 km (62 miles).
Volvo’s aim is to have either ‘mild’ hybrids, plug-in hybrids or battery electric cars by 2021. It plans to sell one million hybrids. Its V40 model will have a choice of engines, plus a rear axle-mounted electric motor.
Hybrid off-road vehicles
Hybrid drive works well off-road. The electric motor increases power. The fossil-fuelled motor extends range. Few however, meet 2020 Euro 7 emissions requirements. Fortunately, many have ample space for batteries. This eases their possibly legally required future conversion.
One example is the Lexus RX 450h. It retains its 3.5-litre V6, but has three electric motors energised by a 123 kW battery. This only marginally increases power (i.e. from 221 kW to 230 kW). It does, however, reduce fuel consumption. That claimed is from 9.6 litres/100 km (62 miles), to a commendable 5.7 litres/100 km.
Lexus 450h. Pic: Toyota
The Mitsubishi Outlander LS and Exceed have a two-litre petrol engine and twin electric motors. They can travel up to 55 km on their lithium batteries. Their claimed fuel usage is 1.7 litres per 100 km (62 miles).
Mitsubishi (2019 Outlander hybrid. Pic: MitsubisiNissan’s
The Nissan Pathfinder Hybrid is available in 2WD or 4WD. Each has a 2.5-litre cylinder supercharged petrol engine of 201 kW and 330 Nm. Its 12.3 kW electric motor is powered by lithium batteries. These are charged by the engine’s alternator, and regenerative braking. Fuel use is a claimed 8.6 litres per 100 km. The battery packs are under the forward-most part of the boot floor.
Subaru’s XV Hybrid uses a 2.0-litre, flat-four direct-injection petrol engine producing 110 kW of power (down from 115kW in the rest of the range) at 6000rpm and 196Nm of torque at 4000rpm. It has a lithium battery and electric motor to assist the petrol engine. It can be driven as electric only, electric motor assist or petrol engine only driving modes.
The Range Rover hybrid has all-new light alloy monocoque construction. It is unusual in being diesel-electric. The 2020 PHEV P400e’s combined power is 297 kW. The maker claims a range of up to 48 km (30 miles) in electric mode. Regenerative braking assists charging.
The Range Rover Evoque hybrid. Pic: landrover.com
The Land Rover is (now) much the same vehicle. It is, however, marketed as a more serious 4WD. It is, however, not necessarily cheaper. A few models (e.g. the LR4 HSE LUX) are more costly than Range Rovers.
Hybrid vehicles and emissions
When comparing emissions, fossil-fuelled power station efficiency needs taking into account. Most convert about 38% of their fuel into usable energy. Petrol burned by cars converts only 25%.
Energy is also lost in producing petrol and diesel. It is also lost in conveying electricity from power station to electric outlets. Furthermore, in charging electric (and hybrid) car batteries.
The National Transport Commission report assesses CO2 emissions intensity of passenger cars and light commercial vehicles in Australia. The data shows average CO2 emissions of all new cars sold in Australia during 2019 was 180.5 g/km. This is far higher than for new passenger vehicles in Europe. There, (using provisional European data) it was 120.4 g/km. Moreover, corresponding figures in Japan and the USA were 114.6 g/km and 145.8 g/km, respectively, in 2017. As that if latest available data, such emissions are almost certainly now even lower.
The National Transport Commission report reveals that Australia’s result is largely due to the increased popularity of dual cab utes and SUVs. These are three largest CO2 contributing vehicle segments. Furthermore, there are also few Australian government incentives for lower emissions vehicles. Moreover, Australia’s fuel prices are low compared with Europe.
In 2019 Suzuki is reported as having the lowest average emissions intensity (128 g/km). Ford is reported as having the highest (210 g/km). A Prius Hybrid emits 107 gram of CO2 per km.
Emissions: petrol versus diesel
On average, the CO2 emissions of diesel cars (127.0 g CO2/km) are now very close to those of petrol cars (127.6 g CO2/km). Moreover, that difference, of only 0.6 g CO2/km, was the lowest observed since the beginning of the monitoring. Diesel emissions, however, are more harmful. Furthermore, they are all-but impossible to reduce much further.
The majority of new SUVs registered are powered by petrol. Their average emissions are 134 g CO2/km. This is around 13 g per CO2/km higher than the average emissions of new petrol non-SUV passenger cars.
See also Electric Vehicles – Thermodynamic Efficiency & Emissions.
Solar-powered electric vehicles
If adequate solar energy is available an all-electric car is virtually non-polluting. There is a minor emission of rubber particles from the tyres. However, there is no equivalent of ‘tailpipe’ emissions.
Battery making, however, is seriously polluting. It is common to hybrid and all-electric cars – excepting that the latter have larger capacity batteries. See also Solar Charging Your Electric Car at Home.
An initially promising all-terrain electric car (the Tomcat) was designed and built in Australia in 2012. The first 100 sold out almost immediately. High manufacturing costs (and investor concerns) resulted in the company entering voluntary administration in February 2018.
The all-terrain electric Tomcat – sadly no more. Pic: Tomcat
The Electric Vehicle Series
This is a part of a series of articles about the history and technology involved in electric hybrid vehicles.
Solar charge your electric car at home
Update 2020
Solar charge your electric car at home
Solar charging your electric car at home or work is totally feasible. This article explains how. Many people already do so. Small electric cars require only a 15 amp power point. The associated cable plugs into the car’s onboard charger.
Virtually all electric vehicles have a charging unit inbuilt. Consult the vendor about charging options.
Pic: SolarQuotes
If used for commuting 40-50 km a day, re-charging requires 2.5-5 kilowatt/hours. One kilowatt hour is often called ‘one unit’. During off-peak periods it may cost less.
Here’s a guide to how many kilometres you can drive before recharging.
| Type | Maximum charge (kW) | km/hour of charging |
| BMW i3 | 7.4 | 25 |
| Chevy Spark EV | 3.3 | 11 |
| Fiat 500e | 6.6 | 22 |
| Ford Focus Electric | 6.6 | 22 |
| Kia Soul EV | 6.6 | 22 |
| Mercedes B-Class Electric | 10 | 29 |
| Mitsubishi i-MieEV | 3.3 | 11 |
| Nissan Leaf | 3.3 – 6.6 | 11 – 22 |
| Smart Electric Drive | 3.3 | 11 |
| Tesla Models S & X | 10-20 | 29-58 |
Solar charge your electric car at home – how to do it
Solar charging your electric car at home or work is feasible. Many existing grid-connect solar systems have excess capacity. You capture solar during the day and sell the excess to the electricity supplier. Then charge the car at off-peak rates at night
Most Australian suppliers ask for about 25 cents per kilowatt-hour (off-peak). That is only slightly less than buying it back off-peak. It pays to shop around. All that’s needed is a quote from one supplier. Armed with that, most existing suppliers will reduce that for a two-year contract. If not, change suppliers. Unlike most products, grid electricity is standardised.
Daytime solar can be re-drawn at night to charge at off-peak rates. Many owners do this. Such charging permits charging overnight, with top-ups as required. Furthermore, it also extends battery life. All dislike ongoing deep discharging.
Using grid power costs only a dollar or two to commute. This is far less than for petrol-fuelled cars. Most use about 7 litres per 100 km. That typically costs (in 2020) about $9/day.
Economy electricity tariffs
Electric cars can be charged on economy electricity tariffs. Charging this way requires a dedicated charging point. This costs about A$1,750. A basic electric car charging unit costs about A$500. More advanced units cost up to A$2500. A licensed electrical contractor will advise re this.
If your charging rate exceeds fuse or circuit breaker rating, they must be upgraded. The cost is not high. Moreover, you save money by switching to such tariffs for charging overnight. You need, however, to install a dedicated charging point. So-using a standard electrical power point is illegal.
Another meter may be needed for the charging tariff. If so, that can be set up by your electrical contractor. Dealers may include an electrician’s advice in the car’s price.
You can reduce costs much further if you charge from a solar PV system. Furthermore, this also reduces carbon dioxide emission.
Charging at public outlets
Fast and super-fast chargers charge at up to 135 kW. They fully recharge an electric vehicle battery in 30 minutes. Owners use these only during long drives. They rely on routine charging at home and at work. Electric car vendors have charging services.
Fast charging facilities exist around Australia. They are even across the Nullabor Plain. See: Charge Stations in Australia (https://myelectriccar.com.au/charge-stations-in-australia). Or ChargePoint. Prices vary from state to state etc.
Electric Vehicle Battery Life
Battery technology is changing fast. Currently, most vehicle batteries’ life depends on their routine depth of discharge. Fully charge the batteries each night and they will live longer.
Most electric and hybrid car makers guarantee batteries for eight years. Nissan allows for 160,000 km, and capacity loss for 5 years or 96,500 km. Australians typically drive 14,000 kilometres a year. This necessitates battery replacing after about eight years. Outright failure, however, is improbable.
Summary
It is already totally feasible to charge cars from home and office solar. Moreover, it is done by many owners right now.
The Electric Vehicle Series
This is a part of a series of articles about the history and technology involved in electric vehicles.
Electric Vehicles Energy Use
Electric vehicles energy use
Regardless of its type of fuel, the energy drawn by any road vehicle is a function of three main factors: air drag, accelerating and braking, and rolling resistance. Electric vehicles energy use is no exception.
The Tesla 3. Pic: Tesla
Air drag
This relates to frontal area and aerodynamics, and particularly to speed. The reason speed so matters is that energy use rises with the cube of the speed). It is thus also affected by driving into prevailing wind. This is not usually a major factor in most countries. It is, however, very much so on Australia’s 1675 km (141 miles) Eyre Highway. Often called the Nullarbor, the highway links South and Western Australia. It is very close to the ocean for much of the way. That wind tends to be either from in front or behind, and can be as high as 30-40 km/h. If driving into the 30 km/h wind at 90 km/h, for electric cars that’s a battery flattening equivalent 120 km/h.
Wind resistance is a powerful reason for driving anticlockwise around Australia. One drives north around September, around the top during winter, then back down the west coast and to where one started in late summer. This should result in a following wind for the west and east crossings.
Electric-only vehicles of today are most suited to urban driving. As battery technology inevitably advances, and charging facilities increase, these will be decreasing issues.
The (2016) Chevrolet Voltec electric vehicle motor and transmission. Pic: Chevrolet.
Acceleration & braking
The energy involved in acceleration and braking relates substantially to the laden weight of the vehicle. Existing batteries are far heavier than their range-equivalent petrol or diesel. An electric vehicle motor and transmission, however, is simpler and lighter. Moreover, it is also 80% to 90% efficient (a fossil-fuelled engine is only 25%).
BMW i3 ultra-light carbon-fibre body shell saves weight. Pic: BMW.
Body shells can be made much lighter: BMW’s i3 electric car has an ultra-light carbon-fibre body shell. This cancels out much of the battery weight. That extra battery weight, however, is expected to be a short-term issue. As our article Electric Vehicle Batteries notes, huge efforts are in progress worldwide to reduce the weight of rechargeable batteries. This will also enable a longer range between recharging.
Rolling resistance
Rolling resistance is directly proportional to minor friction losses, minor heat loss due to tyre wall deflection (<3%), and speed. That of fossil-fuelled,and an electric vehicle’s rolling resistance, is thus the same. There is, however, one considerable energy advantage of electric (and hybrid) vehicle over internal-combustion engined vehicles. It of simple and effective regenerative braking. This recovers the kinetic energy that would be otherwise lost in heat-generating braking. It works by an electric car’s motor momentarily acting as a generator and charging the batteries.
Stop/starting in traffic
In recent years, petrol and diesel engine cars have a (usually optional) engine stop/starting system for use in congested traffic. Whilst this saves fuel, electrical energy is used for each restart. Moreover, electric cars will have a considerable edge as no energy is drawn whilst at rest, nor extra when restarting.
The Electric Vehicle Series
This is a part of a series of articles about the history and technology involved in electric vehicles.
Electric Vehicle History
Electric vehicle history
Electric vehicles have existed for longer than most people think. They long pre-date petrol and diesel. This electric vehicle history by Collyn Rivers is an overview.
The first dc electric motor (1866). Pic: Siemens UK.
The electric battery was invented by Allessandro Volta in 1800. In 1820, Christian Oersted showed electricity could produce a magnetic field. William Sturgeon, (in 1825) invented the electromagnet. Inventors worldwide sought to build an electric motor. They used two main approaches. These were: rotating, or reciprocating (i.e. like early steam engines).
In 1834, Moritz Jacobi invented the first (realistically powerful) electric motor. By 1838 it was improved. It propelled a 14-passenger boat. Meanwhile (1835), Sibrandus Stratingh and Christopher Becker developed an electric motor. It drove a small model carriage. The first electric motor patent was granted to USA’s Thomas Davenport. Many US sources credit Davenport as ‘inventing’ the electric car. It was, however, only a small model. It had negligible power. In 1866, Werner von Siemens developed the basic DC motor. It was this that enabled the first electric cars. DC motors are used to this day.
Electric vehicles were also hampered by lack of stored energy. The only realistic source required constantly supplied diluted acid. These ‘batteries’ were like today’s fuel cells. They combined hydrogen and oxygen to produce electricity. Such batteries worked. There is no record, however, of their powering electric vehicles.
The first lead-acid batteries
In 1859, Gaston Plante developed practical lead-acid batteries. They were bulky and heavy. Nevertheless, they made electric vehicles practical. Their first known usage (1897) was in New York’s electrically-powered taxis.
The first electric powered taxi – New York late 1890s. Pic: taxifarefinder.com
Electric cars’ original acceptance was thus near the end of the 1800s. Most were quieter and smoother than early petrol-fueled cars. Electric cars started instantly. They needed no ‘warming. No gear changing was required. There were even hybrids. In 1916, the Woods Motor Vehicle Company developed a car with both petrol and electrical engines. See Electric Vehicles – Hybrids.
The electric vehicle market was primarily the USA. There was, however, some usage in Europe. London had electrically-powered taxis from 1897. They became known as ‘Hummingbirds’ – due their curious sound.
A London Hummingbird electric taxi – in use from 1897 for many years. They were designed by Walter Bersey.
End of an era
Electric vehicles of that era lacked adequate control technology. This limited speed to about 30 km/h (about 19 mph).
By 1920 or so, road structures (particularly the USA’s) had massively increased. This was particularly inter-city. This required a vehicle range beyond that from batteries. These, however, remained similar in weight and size as 80 years before. Moreover, recharging facilities were inadequate beyond urban areas.
Meanwhile petroleum became increasingly plentiful. This enabled it to power vehicles cheaper and further than electrically. Furthermore, mass production made them affordable. The result was Henry Ford’s (1908) mass-produced model-T. It killed sales of electric cars. Thereon, electric vehicles were used only where limited range was required. It was nearly 40 years before electric cars re-appeared.
In the late 1950s, Henney Coachworks and Exide Batteries developed an electrically-powered Renault Dauphine. It attracted some sales. It could not, however, compete in price with conventional cars. Production ceased in 1961.
General Motors EV1
In 1990 California’s Air Resources Board briefly re-ignited interest in electric cars. Its mandate required U.S. major vehicle makers to have 2% of their products totally emissions-free if used in California. This resulted in General Motors producing its EV1. It was an electric-ony car.
Early EV1s had 16.5–18.7 kWh lead-acid batteries. Later EV1s had 26.4 kWh Nickel Metal Hydride (NiMH) batteries. The car was produced from 1996 to 1999. It was the first mass-produced and purpose-designed electric vehicle of the modern era.
Usage was by leasing only. Customers liked the EV1, but General Motors saw electric vehicles as unprofitable. It sought to cease production. In 2002 EV1 usage was ceased. General Motors repossessed all of them. Most were crushed. A few were given to museums, but with deactivated motors. The Smithsonian Institution has the only intact EV1.
Major US car makers then legally questioned California’s emissions requirement. This resulted in relaxed obligations. That, in turn, enabled developing and producing low emissions vehicles. These included natural gas and hybrid engines, but not (then) electric-only.
The General Motors EV1. Pic: Wikipedia
The right concept at the wrong time
The electric car (and truck) back then was the right concept. But at the wrong time. It awaited control technology, and lighter and smaller batteries.
Control technology then improved dramatically. That of rechargeable batteries, however, did not. Moreover, the size, weight and energy stored in lead-acid batteries remained much as 100 years before.
In 1996, the University of Texas conceived the lithium battery. These store three to four times the energy as lead-acid batteries the same size and weight. They charge quickly and can release huge amounts of energy over a short time.
Now (late 2020), lithium batteries enable electric-only cars to travel 350-550 km (about 220-345 miles) between charges. This is still borderline. It is inevitable, however it is inevitable that battery technology will advance. One thousand kilometres (625 miles) is now seen as feasible. Moreover, so too are electric off-road vehicles.
Further information
It is feasible to use home and other solar (with or without grid-connect) to charge electric cars. For details on using solar to charge electric cars click here. Furthermore, articles on all aspects of electrics cars are being progressively published on this website. Moreover, these will include ongoing details of technology and charging.
The Electric Vehicle Series
This is a part of a series of articles about the history and technology involved in electric vehicles.
Baghdad battery myth
The Baghdad Battery
Was the battery invented over 2000 years ago? The Baghdad Battery remains controversial.
In the 1930s, German archaeologist Wilhelm Koenig was excavating an archaeological dig near Baghdad (Iraq). While doing so, he claimed to uncover a small clay jar. It had a plug that sealed the opening. That plug had a copper tube with an iron rod inserted into it. If filled with an acidic liquid, it functioned as a basic battery. Koenig and others made similar versions that generated up to two volts per unit.
Baghdad battery myth – Koenig’s paper
Koenig is variously claimed to have published a paper on the now-called ‘Baghdad battery’ in a 1938 issue of the German journal Forschungen und Fortschritte. That journal, however, ceased publication in 1967. Digitized (alleged copies) were then posted on several Internet sites. However, no evidence exists of anyone claiming to have read the original paper (if one actually existed).
A drawing of the Baghdad Battery
Koenig’s alleged paper resurfaced in the late 1960s following Erich von Däniken’s controversial book: Chariots of the Gods. This book triggered claims that ‘ancient Mesopotamians had developed batteries.’ Furthermore, that those batteries were used for everything from electroplating jewelry, to powering electric light globes inside Egypt’s pyramids and the lighthouse at Alexandria. The book also led to claims that, since the Mesopotamians did not know how to make a battery or use electricity, they must have obtained this information from someone else. Later speculation, however, suggests he read about it in a paper in the Museum’s archives.
Is the Baghdad battery a myth? – what Koenig described
Koenig described the ‘battery’ as being a flat-bottomed clay jar about 5.5 inches tall, a little over 3 inches across at its widest point, and about 1.25 inches wide at the opening. The jar’s neck was broken off, and there were bits of asphalt adhering to the inside of the rim, indicating the opening had been sealed up. Inside the jar was a hollow cylinder made from a thin sheet of copper. The cylinder’s bottom was covered by a small circle of copper sheets sealed into place by asphalt.
A severely rusted iron rod, about 3 inches long, was inside this copper cylinder. At the top end was a plug of asphalt which fitted into the opening of the copper cylinder. The iron rod projected about half an inch beyond this plug.
Koenig also describes similar clay jars found during excavations near the ancient city of Seleucia. Several clay jars of similar size were found that contained hollow copper cylinders.
These cylinders were sealed at both ends. No iron rods were found with them, but archaeologists found the remains of plant fibers, probably papyrus remnants. The cylinders were found next to a piece of bronze rod and pieces of iron wire.
One clay jar contained a small flask made only of glass. Similar remains had also been found in excavations near Baghdad.
Koenig only suggested these remnants may have been old batteries used for electroplating. He urged that further research be carried out.
This issue then became increasingly improbable. Many ‘paranormal researchers’ took Koenig’s speculation and extended it way beyond what seems reasonable. It was even suggested that technologically advanced extraterrestrials had visited the Earth in ancient times.
Most archaeological studies conclude that the ‘battery’ is simply a (decayed) papyrus scroll. Such scrolls were commonly wrapped around an iron or wooden rod and placed inside a sealed copper tube or glass flask. The now wrapped scroll was then stored inside a clay jar. The jar was then plugged with asphalt to protect it from water and weather.
Koenig’s Baghdad Battery ‘scientific paper’ is hard to take seriously. Some accounts state that Koenig excavated the battery from a site at Khujut Rabu (near Baghdad). Others, however, state that Koenig found the ‘battery’ in storage at the Museum in Baghdad.
Another account suggests the ‘battery’ was found in the ruins of a Parthian (middle Eastern) village dating from 250 BCE. Yet others classify the jar as typical of the Sassanid period – several hundred years later. It is unclear how many ‘Baghdad Batteries’ exist. Most accounts mention just one. Others, however, assert that ten or more have been found.
The object found is a flat-bottomed clay jar. It is about 5.5 inches tall, a little over 3 inches across at its widest point, and about 1.25 inches wide at the opening. The jar’s neck is broken off and has bits of asphalt adhering to the rim’s inside, indicating the opening had initially been sealed.
Inside the jar is a hollow cylinder made from a thin sheet of copper (3.8 inches long and 1 inch wide). The cylinder’s bottom is covered by a small circle of copper sheeting sealed by an asphalt coating. An iron rod (now badly rusted) about 3 inches long is held in place by an asphalt plug. The rod projects about half an inch beyond this plug.
Koenig describes similar clay jars found during excavations at Tel Omar, near the ancient city of Seleucia. Here, several clay jars of similar size were found containing hollow copper cylinders.
These cylinders, Koenig noted, had been sealed at both ends. Archaeologists later found the cylinders had remains of plant fibers, probably the remnants of papyrus. No iron rods were found with them. There were, however, a piece of bronze rod and three pieces of iron wire. One clay jar contained a small flask made of glass but no metal.
Koenig later noted that similar clay jars with copper cylinders and iron rods had been found in excavations by the Berlin Museum near Baghdad, in sites identified as Sassanid. These other finds seem to have become confused by later writers with Koenig’s ‘battery,’ thereby producing confusion about what culture and period the ‘battery’ comes from and how many were found.
Replicas of the Baghdad’ battery’ have been built by several researchers. They typically produce a small electric current (usually between 0.5 to 2.0 volts).
Koenig seems to have wrongly assumed that some ancient metal objects were electroplated – a process using mercury.
The British Museum’s Paul Craddock, however, advises that ‘examples we see from this region and era are conventional gold plating and mercury gilding.’ He states there’s no irrefutable evidence to support the electroplating theory.
Furthermore, David A. Scott, senior scientist at the Getty Conservation Institute, states: ‘There is a natural tendency for writers dealing with chemical technology to envisage these unique ancient objects of two thousand years ago as electroplating accessories, but this is untenable, for there is absolutely no evidence for electroplating in this region at the time.’
These battery-like artifacts may have been storage for important scrolls. They need to be totally sealed. If exposed to the elements for any significant length of time, papyrus or parchment inside would completely rot away – possibly leaving a slightly acidic residue.
Professor Elizabeth Stone of Stony Brook University is an expert on Iraqi archaeology. She states that she does not know a single archaeologist who believes these artifacts were batteries.
The BBC’s MythBusters program built replica jars to see if they could have been used as batteries for electroplating or electrostimulation. One episode had 10 terracotta jars to simulate batteries using lemon juice as the electrolyte. This activated a four-volt electrochemical reaction between copper and iron plates. The show emphasized no archaeological evidence existed for connections between the jars. These are necessary to produce the required voltage for electroplating.
Koenig’s reconstruction of the ‘Battery.’ Pic: Original source unknown.
Other researchers, too, built replicas. If filled with an acidic liquid like grape juice, the ‘batteries’ produced a small electric current of between half a volt and two volts. That has led to several speculations about how the ‘batteries’ could have been used.
One is that the ‘battery’ was connected to small iron statues inside temples. If touched by a worshipper, they would produce a seemingly supernatural tingling that would show the gods’ spirits’ power.
It is known that ancient Greek temples used technological tricks to produce effects, such as doors that opened by themselves or statues that moved to awe worshippers. But there is so far no archaeological evidence that this sort of thing was done in either the Parthian or Sassanid cultures.
There are also problems with constructing the presumed battery. To function as such, it would need to be filled with an acidic liquid. This liquid would need periodic topping up, or be replaced. The jars, however, were sealed with asphalt. Moreover, the copper tube on the inside was sealed at either end. Such construction makes it hard to top up the liquid electrolyte.
The presumed ‘battery’ has no terminals and the iron rod projects beyond the asphalt plug. The copper tube, however, does not. It was thus not possible to connect wires to make an electrical circuit.
It has been suggested that such ‘batteries’ were series-connected (i.e., end to end) to produce a high enough voltage for electroplating. Electroplating, however, is done by placing the metal objects in a liquid through which an electric current is passed. Doing so deposits a thin coating of another metal onto the object.
Such metal coating can also be done by mercury gilding. Gilding involves coating an object with a mixture of gold, silver, and mercury. When heated, this causes the mercury to vaporize. That, in turn, deposits a thin layer of bonded gold or silver onto the intended object. All of the gold or silver plated items found from this period, however, show mercury vapor chemical signature. None exhibit the characteristics of electroplated coatings.
Constructing the presumed batteries presents few problems. Clay jars have existed in the area for thousands of years. Asphalt is readily available in the area. Tar and oil bubble to the surface and have long been used for waterproofing. Copper tubes were often used as protective covers for papyrus scrolls. Iron was a common material for the time. There is nothing unique about the materials used. No advanced technical knowledge is needed to build them.
What was the Baghdad discovery if not a battery?
Archaeologists who study the putative ‘battery’ conclude it is simply a now-decayed sacred papyrus scroll wrapped around an iron or wooden rod. It had been placed inside a sealed copper tube (or sometimes a glass flask). This rod was then stored inside a clay jar and plugged with asphalt to protect it from water and weather. The consensus is increasing that the ‘Baghdad Battery’ is not a battery, but more probably a storage jar for a valued scroll.
Nevertheless, the Baghdad Battery continues to be a source of myth and story. The original, allegedly found by Koenig, was said to have been stored in the Baghdad Museum archives. If, however, it existed, its present whereabouts are not known. It was looted from the museum in Baghdad—along with 15,000 other antiquities—in the chaotic (2004) aftermath of the U.S. invasion of Iraq.
Motorhome Basics
by Peter Manins
Motorhome Information: The Basics
Motorhome basics for those who are occasional motor-homers, who live in a built-up area, and are considering changing to a different motorhome, or who are considering making some improvements to their present one.
Introduction
Here is some information for those who are occasional motor-homers, who live in a built-up area, and are considering changing to a different motorhome, or who are considering making some improvements to their present one. It would have helped me greatly if I had had such a summary a few years ago. Australian Design Regulations (ADR, Ref 1 ) Australian Vehicle Standards Rules (AVSR, Ref 2) and Australian Road Rules (ARR, Ref 3) for motor vehicles are the primary sources, since these are uniform (Ref 1) for Australia or are model rules (Refs 2, 3) adopted by the states and territories. It is also important to observe that a plethora of Australian Standards may also impact on changes you are considering.
Driver’s Licence
Your normal driver’s licence (‘Class C’) allows you to drive vehicles up to 4.5 tonnes gross vehicle mass (GVM, the maximum recommended weight a vehicle can be when loaded). A Light Rigid ‘Class LR’ licence is required for a vehicle with a GVM of more than 4.5 tonnes but not more than 8 tonnes. There are also ‘Class MR’ and ‘Class HR’ licences for even larger vehicles. See e.g. Ref 4.
Comment: To use a normal driver’s licence, the motorhome must not have a GVM of more than 4.5 tonnes. You should know the GVM of your vehicle, and the actual laden weight established by taking it to a weighbridge when set up for typical travel. The handling and safety of a vehicle is greatly affected by its weight, particularly its ability to stop quickly. In the event of an accident your insurance would likely be void if it was found that the vehicle was overweight. Driving a larger vehicle also requires enhanced skills such as correct selection of gears going up and down hills, and tracking around corners — not hard to learn, but essential for safe travel.
Street Parking
Figure 1.
There are significant parking restrictions for larger vehicles and those over 4.5 tonnes. Division 6, Part 12 of Ref 3 notes for Rule 200: (2) The driver of a heavy vehicle, or long vehicle, must not stop on a length of road in a built-up area for longer than one hour, unless the driver is permitted to stop on the length of road for longer than one hour by information on or with a traffic control device, or is permitted to do so by the council.| (3) HEAVY VEHICLE – means, a vehicle with a GVM of 4.5 tonnes or more; LONG VEHICLE – means, a vehicle that, together with any load projection, is 7.5 metres long, or longer; ROAD – does not include a road related area, but includes any shoulder of the road. ‘Built-up area’ is defined in the dictionary. There are restrictions in parking in a Built-Up Area.
Comment: This is a good reason to keep the GVM of the motorhome to no more than 4.5 tonnes: you can legally park it in the street of your suburb and in other towns. Annual registration and third party insurance costs increase considerably for larger vehicles.
Width
Figure 2.
Rule 43/01, Sec 43.4.5.1 of Ref 1 notes (1) A vehicle must not be over 2500 mm wide (including any load projection). (2) For subclause (1), the width of a vehicle is measured without taking into account any anti-skid device mounted on wheels, central tyre inflation systems, lights, mirrors, reflectors, signalling devices and tyre pressure gauges. Overall vehicle width includes ‘load projections’ such as awnings but not mirrors. Comment: Not all motorhomes on Australian roads begin their life complying with this requirement. See also ‘Load Projection’.
Load Projection
Figure 3.
Figure 4.
Rule 43, Sec 43.5.1 of Ref 1 also notes For vehicles any ‘Equipment’ shall not project more than 1200 mm from the ‘Front End’ or ‘Rear End’. Defining Load Projection at the front (from Ref 5, © VicRoads with permission). From Ref , anything added to increase the overall width of the vehicle must be less than 150 mm in width. This Rule is an extension of AVSR (Ref 2) and has been adopted by most Jurisdictions. Defining Side Load Projection (from Ref 5, © VicRoads with permission).
Comment: A common problem here is that an awning mounted on the side of a large motorhome takes it over the legal width of 2500 mm. A Porta Bote, mounted on the side of my Ducato motor camper, projects less than 140 mm (including brackets), and the overall width is still less than 2500 mm, so is legal. Figure 6 shows the rig on tour.
Rear Overhang
Figure 5
Rule 43/03, Sec 6.2.3 of Ref 1 states: 6.2.3. For all other motor vehicles and trailers (other than ‘Semi-trailers’) the ‘Rear Overhang’ must not exceed 60 per cent of the distance from the centreline of the front ‘Axle’ to the line from which ‘Rear Overhang’ is measured, or 3.7 metres whichever is the lesser. The Load Projection (if any) is included in this calculation. . Defining Rear Overhang (R/OH) relative to Wheelbase (WB) (from Ref 5, © VicRoads with permission).
Comment: This requirement causes lots of grief for those wanting to mount tool boxes or motorcycle carriers on the back of motorhomes that already have substantial rear overhang (let alone the structural engineering issues). A carrier must either be folded into a vertical position or removed entirely when not being used to carry a bicycle or motorcycle and any loading ramp must only deploy to the left hand side of the vehicle. For my Ducato, the wheelbase is 3700 mm so the maximum legal overhang is 2220 mm. The overhang of the body is 998 mm, so the maximum overhang of any additional equipment is restricted to the Load Projection Rule of 1200 mm. My bicycle mounting method complies: the bicycles overhang by 920 mm and the carriers fold up when not in use. My A’van Applause on Ducato with side load and rear loads.
Visibility of Number Plate
Figure 7.
The following Figure (Fig 7) and Clause are from Ref 6. Clause 61(2)(c) of Schedule 2 of the Regulation requires that a number-plate must be visible at a distance of 20 metres from it and within all the areas described by an arc extending at an angle 45° above the top of the number-plate and 45° forward of its edges. Number plate visibility requirements (from Ref 6, NSW Roads and Maritime Services with permission). Comment: The number plate must not be hidden by bicycles etc., mounted on the back of the motorhome. My rig is compliant with one bicycle mounted, but perhaps not so with two (see Figure 6); a bicycle rack number plate may be necessary.
Figure 6.
Bull Bar
Figure 8.
Adding a bull bar to a motorhome is a popular modification, but is fraught with problems. As explained in the Queensland regulations, Ref 7 Bull bars must be free of sharp protrusions and all exposed sections of the bull bar and fittings must be radiused and deburred. Forward and side members should be designed to reduce the risk of injury to any person who may come into contact with the bull bar. A potentially dangerous bull bar on a vehicle in St George, Q’ld (7 Oct 2011). Vehicles fitted with an airbag or manufactured to comply with ADR 69 – Full Frontal Impact Occupant Protection or both ADR 69 and ADR 73 – Offset Frontal Impact Protection, can only be fitted with a bull bar which: • has been certified by the vehicle manufacturer as suitable for that vehicle or • has been demonstrated by the bull bar manufacturer to not adversely affect compliance with the ADRs or interfere with the critical airbag timing mechanism, as the case may be. Comment: A bull bar is commonly fitted to protect the vehicle against animal strikes. It is far more important not to compromise the safety of the vehicle and occupants in the event of a crash. Finding a bull bar that is certified as compatible with the airbag timing mechanisms of a modern vehicle is a challenge! The danger from a bull bar to pedestrians is also important.
Gas and Electrical changes
Rule 44/02 of Ref 1 states (Clause 44.8.2) that …liquefied petroleum gas installations in motorhomes and travel trailers shall comply with the requirements of “Code Governing the Installation in Travel trailers of Liquified Petroleum Gas Equipment and Appliances”, issued by the Australian Liquified Petroleum Gas Association. The Rule gives legal force to the relevant parts of Standard AS/NZS 560.2.2010 – Gas Installations. Changes to the electrical installation are also subject to Australian Standards. In some States these are mandated with legal force. From Ref 8 The electrical installation in your motorhome or travel trailer must be undertaken and certified by a registered electrical worker in accordance with Australian Standard 3001 and issued with a Certificate of Compliance. Comment: There appears to be some confusion in some jurisdictions (Victoria in particular) about the legal force behind Australian Standard 3001 for motorhomes and travel trailers. For safety’s sake, there should be no doubt!
Motorhome basics comment
If you want to read more about my experiences with my Ducato A’van Applause 500 motor camper, see http://manins.net.au/motorhome/sitemap.html. Happy travelling!
Words, photographs and illustrations, except as otherwise credited, by Peter Manins.
Article: copyright 2012, Peter Manins.
References
1. Australian Vehicle Design Regulations, https://www.infrastructure.gov.au/infrastructure-transport-vehicles/vehicles/vehicle-design-regulation/australian-design-rules
2. Australian Vehicle Standards Rules, http://ntc.wdu.com.au/filemedia/Reports/AVSRs8thPkgExplanationDoc.PDF
3. Australian Road Rules, http://ntc.gov.au/roads/rules-compliance/about-the-australian-road-rules/
4. Australian driver’s licenceshttp://www.rms.nsw.gov.au/roads/licence/index.html
5. vrpin01833.pdf which is linked from http://www.vicroads.vic.gov.au/Home/Moreinfoandservices/ HeavyVehicles/InformationBulletins/RearOverhangLimitsforCarsTrucks.htm
6. http://www.rms.nsw.gov.au/documents/roads/safety-rules/standards/vsi-58-number-plate-visibility.pdf
7. pdf_modification_motor_vehicles2.pdf linked from http://www.tmr.qld.gov.au/Safety/Vehicle-standards-and-modifications/Vehicle-modifications/Light-vehicle-modifications.aspx
Truck wind forces on travel trailers
by Rob Caldwell
Truck wind forces on travel trailers
This paper explains how overtaking a fast moving truck, or being passed by one can exert dangerous truck wind forces on travel trailers.
The original of this paper ‘Travel trailers and Trucks Sharing Roads in Australia’ by Rob Caldwell MITE (Life) MAITPM (of Caldwell Consulting) was published in 2012. This is Mr Caldwell’s 2014 updated version. (Minor typographical changes have been made to suit the webpage format.)
Truckies are working in a high pressure transport industry, trying to maximize their efficiency by traveling at near the speed limit, right on the speed limit, or creeping just over the speed limit. Their workplace is on the road, and a major part of their profession is to tolerate traffic situations and share the road with others. Truckies have regulated work hours and can work up to 12 hours a day, with 7 hours of stationary rest.
RVers are on holidays, either touring or heading to a long stay vacation at their favourite [caravan park]. They are generally not in a hurry, and tend to travel considerably under the speed limit, and therefore, at a considerably slower speed than the trucks. They usually travel for 4 to 6 hours in a day and have 16 to 18 hours of stationary rest
It is a pretty big conflict of interest on our roads, and this conflict is probably a major contributing factor in travel trailer crashes.
Every travel trailer tow vehicle (tug) driver has a responsibility to share the road with others, particularly in the area of co-operation with the truckies and helping them to share the road.
How RVers can help
The first recommendation to travel trailer tug drivers is to acquire a UHF radio and use it to communicate with the truckies (ie Channel 40 and 29…not 18). If this can be achieved nationally and quickly, the traditional bad language could diminish considerably, and may even disappear if the women in travel trailers can make their presence heard. The truckies will quickly learn of the benefits of communication with RVers if the actions set out in this document are adopted by caravanning road users.
Meeting trucks on the road
A truck [in Australia] can have a maximum width of 2.5 metres (8 ft 3 inches.) Travel trailers can also be up to 2.5 metres, and tow vehicles are usually less than 2.0 metres wide.
A truck passing a travel trailer, with a metre (about 3 ft 3 inches) between them will require a 6 metre (20 ft) wide road surface. Most rural two lane highways built in Australia up to the 1960’s had a maximum width of bitumen of 6.1 metres, or 20 feet. Most rural main roads had a width of only 5.5 metres (18 ft). Many shire roads that were sealed in the 50’s and 60’s had a bitumen seal width of only 4.9 metres (16 ft). Many outback roads, when they were first sealed had a seal width of only 3.66 metres (12 ft).
Many of these roads in Australia have not been widened, even though the maximum allowable width of vehicles increased from 2.4 metres to 2.5 metres in the mid 1970’s. So, we must learn how to drive on these roads and share them with others, including the monster trucks. Of course some major roads have been widened to 7 or 8 metres, and some of them now have sealed shoulders.
The wind that the trucks push is a hidden force
All RVers will have experienced the buffeting wind that comes from a passing truck, either in the opposite direction, or when the truck is overtaking your travel trailer. Cab- over or flat fronted trucks produce a stronger “bow wave” of wind than trucks with long bonnets over the engine and some trucks may have more than one “bow wave”, depending on their configuration and load. For example, a low loader with rear ramps in their upright position and no load, can produce a “bow wave” from the ramps, and likewise, a road train with a high load on the rear trailer.
The force of wind can be so strong that it affects the line of travel of your rig. Over- correcting in these situations can lead to loss of control, a collision with the truck, or jack- knifing, possibly ending in vehicle roll-over, on or off the road.
Understanding the dynamics of these instances, and knowing how to apply remedial action can avoid a disastrous event.
The on-coming truck
If the road is line marked with only a centre line, (ie, no edge lines), the road may not be wide enough for the truck and car to pass without one vehicle or the other having to drive with left wheels on the shoulder. The travel trailer should slow down and very gradually move to the left so that the left wheels are off the bitumen, then, after the truck has passed, wait until there is a smooth path back on to the bitumen, and very gradually move back on.
Any sharp change in direction or speed whilst the left wheels are off the bitumen can lead to instant loss of control. Do not brake hard in this situation because your right wheels will have more effective braking ability, resulting in the vehicle veering sharply back onto the road and into the path of the truck.
If there is no centre line, the bitumen road width is likely to be only 4.9 metres (16 ft.) (4.9 metres), or even 3.7 metres (12 ft.). Call the truckie on your UHF40 and tell him to “STAY ON” as you are going to slow down and pull off the road. That way you will not only gain appreciation from the truckie, but you will avoid being showered with rocks and gravel which would happen if the truck had to leave the bitumen.
If the road is line marked (in accordance with Australian Standard AS1742) with a centre line and, edgelines on both sides, it will be wide enough for the truck and the travel trailer to pass without any wheels leaving the bitumen.
Apart from driving as far to the left as possible, the travel trailer towing driver must be prepared for the wind forces that will be exerted by the truck. It is a good idea, if, when you are travelling on an empty road (no other vehicles behind, in front or coming towards you) to practice, using your left side mirror, to drive so that the travel trailer wheels are just touching the edgeline. You can then establish a relationship between the left front of your vehicle, and the edgeline so that you can drive as close as possible to the edge of the road, without having the travel trailer wheels drop off the bitumen.
A bit of practice and you will be in the best position without having to glance across to the mirror.
So, when the front of the approaching semi-trailer is passing the tow vehicle, you will feel the buffeting of the bow wave of air that the truck is pushing at 100 km/h. Your vehicle has wheels on each corner and the force of the wind should not affect the stability or direction of travel. When the bow wave hits the front of the travel trailer, as shown in Diagram 1 [shows] the force will have a severe effect on the stability of the travel trailer, The van is connected to your vehicle at the towball, which is a single pivot point, or fulcrum. The travel trailer’s wheels are in the middle of the van and therefore the centre of the axle(s) is another pivot point.
Diagram 1. The force of the bow wave will push the front of the van towards the left side of the road, pivoting at the towball and the centre of the van’s axles. This subsequently creates a force at the front of the tow vehicle towards the truck. Added to this is the suction of air, back in towards the prime mover’s driving wheels, the ‘eddy’, or ‘vortex’ behind the bow wave.
As the bow wave passes the van’s axles, (Diagram 2), the pressure on the side of the van will push the back of the van towards the edge of the road, with subsequent forces pushing the front of the van towards the truck, (aided again by the suction of the eddy) and the front of the tow vehicle towards the left. If not counteracted by the driver, this could develop into a harmonic motion of opposite direction swaying, which can increase to a point of total loss of control, jack-knifing and then roll-over. End of holiday!
Hold the steering wheel firmly with both hands tightly, the left hand at ’10 o’clock’ and the right hand at ‘2 o’clock’. Compensation for the changes in force that contribute to the bow wave of the truck are by pressure only…..do not attempt to steer in the opposite direction to that of the force.
Remember a truck travelling towards you can be doing 100 km/h and if you are doing 90 km, the closing speed is 190 km/h. The truck will take only 0.2 seconds to pass you and you won’t have time to compensate for the change in forces anyway.
If your rig does start a harmonic motion, take your foot off the accelerator and slowly apply the brakes of the travel trailer. If you don’t have an electric brake controller with a manual over-ride, gently apply your foot brake, keep the tow vehicle pointing straight ahead and keep slowing until the rig is stable. Don’t try to accelerate away from the sway and don’t hit the brakes hard.
The overtaking truck
This can be a much more dangerous situation for the Travel trailer and I believe it may be a major contributory factor in the occurrence of jack-knifing and rollovers involving travel trailers. If you are travelling at 90 km/h, and a 25 metre long B-Double is travelling at 100 km/h, you will be subjected to the forces of truck generated winds for some 21 seconds, until the back end of the truck has passed the front of your vehicle. (Note: the times are measured from when the front of the 25 metre B-Double is 10 metres behind your 13 metre long rig, until the rear of the B-Double is 10 metre clears of the front of your tug.). If the truck is a 55 metre long, four trailer road train, as you would encounter on the Great Northern Highway (WA) or the Stuart Highway (SA & NT), it will take 32 seconds to pass.
If you are on a two way road and you see the truck approaching from behind, call him up on Channel 40 and tell him that, ‘As soon as you’ve pulled out, I’ll back off’ . Do not back off until the whole of the truck is ‘out’ in an overtaking position. When the rear of the truck has cleared the front of your vehicle, flash your lights or call “You’re clear’ on the radio. This will gain a lot of appreciation from the truckie as, if you can slow to 80 km/h it will reduce the overtaking time by half, to 10.5 seconds. The truckie will thank you, either by calling on the radio, or by flashing his right turn indicator light, and then the left turn indicator light. At 80 km/h, you will be in a better position to handle the forces of the truck’s bow wave, eddy and following turbulence.
[The following diagrams and pictures show the sequence.]
Diagram 3.
Diagram 4.
As the front of the truck reaches the rear side of your van, the bow wave will push the back of the van towards the edge of the road (Diagram 3), and the front of the van will be pushed towards the truck, pivoting at the van’s axles. (This will be more pronounced with a single axle travel trailer). The front of your tug will feel as though it is veering to the left. Do not try to turn the steering wheel to the right to compensate.
As with the approaching truck, keep your hands firmly at “ten and two” and concentrate on keeping a straight course. You will feel the pressure of the “force to the left” but your firm grip will compensate for the pressure. Next you will feel pressure to the right as the bow wave hits the front side of the van, pushing the A frame towards the left. (Diagram 4) The eddy, (or vortex) behind the bow wave, will tend to “suck” the rear of the van towards the truck, and this will exacerbate the forces. The front of your tug will feel as if it is veering to the right, towards the front of the truck.
You will next feel the bow wave hit the rear side of your tug (Diagram 5) and the eddy will draw the front side of the van towards the truck.
Diagram 5
Diagram 6.
The bow wave will then force the front of your tug to the left (Diagram 6) and the van will tend to be sucked towards the truck by the eddy. As the front of the truck passes the front of your tug, you will feel as though you are being sucked towards the bogey wheels of the truck. (Diagram 7.) This again is the force of the eddy behind the bow wave.
Diagram 7.
Finally, as the rear of the truck’s trailer passes, (Diagram 8), you will feel the buffeting of the “wake” and turbulence. This again will tend to pull the van towards the truck, but the forces will not be as great as they were in Diagrams 3 and 4.
Diagram 8. The forces exerted by the winds of an overtaking truck can set up an harmonic motion which could end up in a situation as shown in the following photograph.
This scene was on the Pacific Highway near Coolongolook.
In this instance the momentum that could have contributed to the disaster would be exacerbated by the weight of the large outboard motor, spare wheel, and generator attached to the rear of the van and, the distance between this weight and the centre of the van’s axles.
The swaying in harmonic motion produces an inertia about the centre of the van’s axles. Inertia is measured by multiplying the weight (of the attachments) by the square of the distance between the attachments and the axles of the van. So, if the spare wheel was there when the travel trailer was purchased, and weighs 40 kg (88 lb) and is mounted 3 metres to the rear of the centre of the axles, the inertia is 360kgm2. If the outboard motor weighs 50 kg (110 lb) and the generator 25 kg (55 lb) and the mounting hardware 15 kg (33 lb)., the combined weight is 130 kg (285 lb). The centre of this mass has probably moved to 3.2 metres from the centre of the axles and the resulting inertia is a massive 1331 kgm2.
I have heard some say that they have added weight on the A frame to ‘balance’ the rig and keep 10% of the GTM [Gross Trailer Mass] on the tow ball. For example, a folding boat trailer, jerry cans and boat fuel tanks. Well, this again is adding weight at some 3 – 4 metres away from the axle pivot point. This will add to the inertia when the van begins swaying.
The travel trailer rig overtaking a truck
Occasionally, there may be a need for vehicle towing a travel trailer, to overtake a truck. This manoeuvre has the potential for an even more disastrous result, simply because the travel trailer rig must travel faster than the truck. The wind forces are a mirror image of the overtaking truck situation described before.
Event No. 1. Tug enters vortex and is drawn towards the truck.
Event No. 2. Tug hits bow wave with forces to the right, and front of travel trailer is in vortex, drawing towards the truck, setting up the harmonic motion.
Event No.3. Bow wave hits front of travel trailer and rear of travel trailer is drawn into vortex, exacerbating the harmonic motion.
Event No. 4. Rear of travel trailer hit by bow wave forcing it violently to the right.
Event No. 5. Travel trailer releases from bow wave, swinging back towards the front of the truck.
Event No. 6. Harmonic motion swings van from side to side. The black skidmarks are from the car braking hard. There are no travel trailer braking skidmarks, only yaw marks as the travel trailer swings back to the left. Driver has totally lost control.
Event No. 7. Tow vehicle braking skid marks turn to yaw marks. Left wheel of travel trailer starts yaw mark. Car broadsides off road, left wheels drop down embankment, digging in and causing vehicle to roll, travel trailer roll follows.
On a flat, straight stretch of outback highway, (possibly with a speed limit of 110 km/h), the truck is probably travelling at 100 km/h. It is estimated that the travel trailer rig is about 10.5 metres in overall length. It took the rig two seconds to pass a reference point on the truck. (ie, 5.25 m/sec faster than the truck). The calculations show that the travel trailer rig was travelling at 119 km/h. as it passed the front of the truck. If the truck was doing 95 km/h, the travel trailer rig was doing 114 km/h.
In reality there were two ways to avoid this crash:-
- Don’t try to overtake a truck at high speed….stop and have a cup of tea! and,
- If you must attempt to overtake, make sure you have electric brakes fitted to the travel trailer, with a manual override – do not apply the car brakes if swaying commences. Activate the travel trailer brakes manually, and steer your car straight ahead until the rig has stabilized. By this time the truck will have most likely continued on, and you will need to stop and have a cup of tea!
On multi-lane roads, travel trailer rigs will often have to pass trucks and, of course, the same truck wind forces will be experienced. On these roads the lanes may be a little wider and the shoulders are usually sealed. This gives the Travel trailer the opportunity to pass with a larger gap between the truck and the travel trailer, thereby reducing the impact of the wind forces.
Harmonic motion can affect other things too
A most graphic display of wind force setting up increasing harmonic motion, or oscillations, was the spectacular destruction of the Tacoma Narrows bridge in Washington State, USA in 1940. There are many photos and films of this event and it is certainly worth a Google – Just type in ‘Tacoma’ and have a look. The contributory factors were given as :-
- Random Turbulance
- Periodic vortex shedding and,
- Aerodynamic instability.
Perhaps we have a correlation here, with the random turbulence being the bow wave, and eddy (or vortex behind the bow wave) and the periodic vortex shedding being the effect of the truck wind forces on the side of the van. The aerodynamic instability, or what I have referred to as harmonic motion, is probably related to the fact that the towing vehicle has 4 wheels, each near a corner of the vehicle, and the single pivot point connection to a van that has the wheels in the centre of the vehicle.
Perhaps travel trailer manufacturers should be looking at building a van that has a front and rear axle, like the dog trailers behind tip trucks. The example below may be very difficult to control direction when reversing. [Please see Editor’s note at the end of this article re the believed source of this travel trailer.
A 4-wheel travel trailer with axles fore and aft. The steering may be difficult to control when reversing.
To my knowledge, there has not been any scientific studies made to analyze the forces of deflected wind created by an overtaking truck, yet, the situation arises more frequently on our roads as old two-way highways are replaced by divided roads. How often do we hear that traffic on the freeway has come to a standstill because a car and travel trailer has jack-knifed?
Whilst truckies must have a special heavy vehicle driver’s licence and must undertake mandatory training in handling their rigs, car drivers who are towing travel trailers have not had any training in handling their rig, unless they have attended a towing course of their own choosing and expense. Most simply assume that as they are licenced to drive a car, they are capable of towing a travel trailer. To my knowledge, towing courses do not address the issue of wind forces from trucks and the subsequent potential of harmonic motion causing loss of control.
There are several towing guides, brochures and booklets published by road authorities, motoring organizations, insurance companies, and travel trailer magazines, very few of which address the issue of wind forces from trucks.
An exception to this is the NRMA’s ‘Towing in Australia – Pain or Pleasure’ (about 1983) booklet which contains the following advice on the last page:-
”Travel trailer stability is also seriously affected when the combination is passed or being overtaken by larger tankers or semi-trailers.
Wind forces from the front of large vehicles strike the side of the travel trailer and force it to the side of the road. Alternatively, when being overtaken, and the large vehicle passes the centre of the travel trailer, suction from the rear of the passing vehicle will tend to draw the travel trailer to the centre of the road. This causes the travel trailer to oscillate about its centre of gravity and applies forces to the tow ball, making the car become unstable. In really serious cases, this can cause the trailer combination to go completely out of control and jack-knife. To reduce this dangerous tendency, try to increase the distance between the travel trailer combination and the passing vehicle.
Tests show that for two vehicle passing at 80 km/h. suction force on the travel trailer is reduced two-and-a-half times when the clearance between the two vehicles was increased from hald a metre to two metres. On seeing that you are likely to be overtaken, maintain the current line of direction on the trafficable portion of the carriageway until the approaching vehicle has commenced overtaking, then reduce speed and move as far to the left as possible. . . . “
![Truck wind forces on [cara_s] - electric vehicle batteries,book on batteries,electric car batteries,lithium ion batteries for electric cars,electric car battery technology,how long do electric car batteries last,electric vehicle battery life](https://solbsau.centrails.com/wp-content/uploads/2020/03/NRMA-Towing-in-Australia-Pain-or-Pleasure.jpg "Truck wind forces on [cara_s] 63")
This section needs to be updated to reflect the higher speed (100 km/h) of heavy vehicles, the size of the vehicles, especially the “Cab-over” flat fronted trucks, and the available lateral road space available. There is no mention of electric brakes, anti sway control and, the last line is certainly not appropriate when the speed is 100 km/h.
The Travel trailer and Camping Industry Association of NSW, in their publication, ‘The National Travel trailer and Recreational Vehicle Towing Guide’ does raise the issue, but only recommends that: ‘if these forces are noticeable after fitting an appropriate weight distribution hitch, an added sway control unit should be fitted’.
There is a clear need across all levels of Government, the media, and all organizations associated with caravanning, to provide education, training and re-training of drivers who are towing travel trailers and camper trailers. There has been many fatalities, serious injuries and family trauma resulting from ignorance and lack of knowledge in travel trailers and trucks sharing the road.
Rob Caldwell ( MITE(Life), MAITPM) – Traffic Engineer. August 2010 (Updated August, 2014).
Footnote: I do not know the persons who are responsible for the photos in this report, but I thank them, as it is hoped that this report will make a contribution to greater safety.
RV Books thanks Mr Caldwell (and Caldwell Consulting) for enabling this paper to be reproduced. Caldwell Consulting can be contacted at P.O. Box 476, Nelson Bay, NSW 2315.
NOTE from Collyn Rivers, RV Books
The ratio of travel trailer side area front/rear of the travel trailer rear axle can affect this issue profoundly (some travel trailer owners will experience it more than others but the effect always presents risk). This issue was well understood by legendary travel trailer builder Barry Davidson. His Phoenix series had sloping sides at the front. That and well set-back rear axle/s resulted in one of the most stable travel trailers yet built.
(The dog axle [cavaran] pictured is understood to have been built by Spaceland (any more information appreciated).
Collyn Rivers.
Warning for Potential Travel Trailer Buyers – how to buy a travel trailer
Warning for Potential Travel Trailer Buyers
Travel trailer industry insiders express concern that too many manufacturers and importers compete in a limited and highly competitive market, hence this warning for potential travel trailer buyers – how to buy a travel trailer. RV Books shares this concern.
Potential buyers need to ensure their proposed travel trailer complies with Australia’s safety regulations. These are currently (early 2021) in the Australian Design Rules. The Federal government’s Vehicle Safety Standards branch, however, recognises there are problems in Australia’s travel trailer industry. Its new Road Vehicle Standards Act is effective from July 2021. This Act replaces the 1989 Motor Vehicle Standards Act.
The effect of inadequate rust protection.
Road Vehicle Safety Standards Act
The 2021 Road Vehicle Safety Standards Act allows larger travel trailer companies a lengthy period to meet the new requirements. Hence, it is likely the new law’s intended benefits will not become apparent until mid-2022.
The travel trailer industry veterans warn there are non-compliant travel trailers. The new regulations, however, do not guarantee all future travel trailers will be fully compliant. Nor do these regulations apply to manufacturers and importers. Some companies that produce travel trailers in small numbers will be exempt. So will be industry newcomers.
Not all makers have the resources and experience essential to manufacturing safe, high-quality travel trailers. Also lacking are standard professional after-sales service and repair facilities.
Unfortunately for owners of defective or non-compliant travel trailers, the new Act is not retrospective. Affected owners can only continue to pursue action against the selling dealer. Not the maker.
Australian Consumer Law
Australian Consumer Law protects customers who bought unsatisfactory or unsafe products. Dealers, however, may attempt to avoid their responsibilities. Some advise buyers to seek redress from the travel trailer maker. If that happens, consult a lawyer. Whoever sold you the travel trailer is legally liable.
It is vital that potential buyers do their homework thoroughly before deciding on a particular make and model.’ Furthermore, ‘that a salesperson does not persuade them to buy a better (i.e. higher-priced) travel trailer, which may or may not, live up to promises made.
How to buy a travel trailer
Buying a travel trailer is a significant investment. Make the purchase on a practical basis, not emotional. Moreover, sales staff are professionally trained to sell. Travel trailer buyers, however, are not trained to buy. As a result, buyers are likely to suffer remorse when they realise their purchase lacks expectations.
Travel Trailer Length and Stability
Travel Trailer Length and Stability
Travel trailer length and stability interrelate. The tow vehicle should weigh at least the same as the travel trailer. Excess travel trailer weight is undesirable. Excess travel trailer length, however, is more significant. Limit travel trailer length, and weight at either end.
Extreme travel trailer rear-end weight is particularly undesirable. Many travel trailers have about 110 lbs (about 50 kg) of spare wheels on their rear wall. The effect of that weight when pitching or swaying is many times more. If at all feasible, relocate those spare wheels onto a cradle underneath the travel trailer‘s chassis, or carry in the tow vehicle. Also, why two spare wheels? Tow vehicles normally have only one.
Travel trailer length and stability interact
A travel trailer towed via an overhung hitch is fundamentally unstable. Ample tow ball mass (e.g. 10%) is vital. There is nevertheless a speed at which travel trailers will sway. Friction and other mechanisms dampen that sway. They may not do so sufficiently in an emergency swerve to prevent the rig jack-knifing. This is particularly an issue in the USA. People there claim to tow long and heavy ‘travel trailers’ behind often lighter vehicles. Some do so at a claimed 160 km/h (100 mph). That is virtually a recipe for swaying. Or worse.
Travel trailer length and stability – how to ensure it first and every time
It is possible to design (and load) a travel trailer such that it will normally only sway at speeds as high as 160 km (100 mph) but that speed is better avoided. All this, and a great deal more is explained in RV Books’ top-selling Why Caravans Roll Over – and how to prevent it .
RV Books also publishes How to Choose and Buy an RV, Travel trailer & Motorhome Electrics, The Camper Trailer Book, Solar That Really Works (solar power for RVs) and Solar Success (for homes and properties).
Making stable travel trailers – here’s how and why to do it
by Collyn Rivers
Making stable travel trailers
Making stable travel trailers is readily possible by design, loading, and tow vehicle use and choice. This article by Collyn Rivers explains how. It also provides practical guidelines for buying a travel trailer and tow vehicle, their loading, and their on-road usage. For a full technical explanation of why rigs can be unstable please see my Travel trailer and Tow Vehicle Dynamics/. See also Why Caravans Roll Over/
Making stable travel trailers is always desirable. For Australian (and USA) travel trailers it is essential. Such trailers are increasingly heavier and (worse) longer, yet tow vehicles are increasingly lighter. Accidents have escalated since 2014.
According to one major insurer loss of control accounts for over 90% of all rollovers. ‘ In all cases’, stated that insurer ‘the travel trailer began to fishtail and the driver was unable to bring it back under control.’ Such ‘loss of control’ appeared due to various causes. These include incorrect loading, inadequate tow vehicle weight, excess travel trailer weight, excess hitch overhang, driver error. And particularly speed. It did, however, overlook that most were long twin-axle units.
An only too typical travel trailer roll-over. Pic: original source unknown.
Making stable travel trailers – weight
Many travel trailers built since 2015 are over 6.5 meters. They weigh well over 2000 kg (4400 lb). Some are 7-9 meters and weigh over 3500 kg (7700 lb). A few are over 4000 kg (8800 lb). Many are towed by vehicles far lighter than the trailer. And at 100-110 km/h (plus 60 mph). Worse, an Australian travel trailer magazine stated that many travel trailers reviewed were heavier than their makers claimed.
Before finalizing payment for any travel trailer, weigh it on a certified weighbridge. Never assume the claimed Tare Mass is correct. Few are. That weight is as the unit left the factory. It does not include water. Nor (usually) optional extras originally ordered. Any weight over its actual Tare Mass reduces that for personal effects pro-rata.
Overall length
Whilst excess weight is undesirable the major factor determining a travel trailer‘s stability is its length. In particular the distance from its tow hitch to its axle/s. Known as the ‘radius of gyration’, the greater that is the better. Also assisting stability is the tow vehicle’s wheelbase (i.e. the distance between its front and rear axle). Here, the longer the better. By and large, however, it is excess travel trailer length and where weight is distributed along that length that is now the major issue,
Weight distribution truly matters
That not generally understood is that towing stability is substantially related to a travel trailer‘s length. In particular, where weight is distributed along that length.
A dangerous assumption (still found on RVs forums) is that as long as recommended nose mass is retained, a travel trailer can be loaded as wished. An extreme example, seen at a camp-site, had a motorcycle on its rear. The motorcycle was ‘balanced’ by 200 kg (440 lb) of barbell weights on the trailer’s A-frame. Another was a widely spread article suggesting that tow ball mass be adjusted via sandbags at the trailer’s front end – a seriously bad way of adjusting tow ball mass.
The ideal travel trailer has its axle/s set way back. Then laden with everything heavy as close to the axle/s as possible.
Never locate anything heavy (particularly high-slung spare wheels) at a trailer’s extreme rear. Locating a tool-box on a rear bumper is an absolute no-no. At the front, for stability, the longer the A-frame the better.
Tow ball mass
For a trailer towed via an overhung hitch, to be stable it must be nose heavy. There is a known relationship between its nose weight and speed. The lower that nose weight the lower the safe speed.
Australian trailer makers initially recommended a nose mass of about 10% of the laden weight. Ongoing emission legislation, however, causes vehicle makers to reduce their products’ weight. As a result, trailer makers reduce their nose mass recommendations. Or, and increasingly, do not advise it. While that 10% is still really required, that often now exceeds current tow vehicles’ ability to support it.
The average maker-recommended tow ball mass of typical 2020 Australian-built travel trailers is now 5%-7%. One is a mere 4.0%. Only a few remain at 9% to 10%. Some makers suggest towing with the water tanks empty. That seemingly negates having them.
European travel trailers are about 40% lighter (per metre) than most local products. There, 7% has long been seen adequate (and still is).
Legal reasons preclude suggesting anything other than: ‘follow what the travel trailer maker recommends’ re tow ball weight. RV Books does not, however, endorse such recommendations.
Hitch overhang
Another major factor in trailer stability is the length from the tow vehicle’s rear axle to the overhung tow ball. The less that overhang, the less a travel trailer‘s tendency to pitch and yaw. The average overhang of Australian tow vehicles is 1.24 metres. The longest (well over 2 metres) are mostly extended chassis dual-cab utes. It is not a coincidence that many roll-overs involve such vehicles.
When making stable travel trailers, the tow hitch too should have the minimum possible overhang. Reducing that alone assists stability.
Excess hitch-shank length like this should be avoided. Some hitches have adjustable shanks. If yours is like this, fit one that is shorter. Or have an engineer drill a new hole.
Weight Distributing Hitches
The heavy tow ball weight imposed on an overhung hitch pushes down the rear of the tow vehicle. It acts as a lever. As with a heavy person at one end of a see-saw, it levers up the front wheels of the tow vehicle. A weight distributing hitch is simply a springy lever. Its effect is to force those wheels back down.
This effect is often misunderstood. A WDH cannot reduce the side forces resulting from cornering or yaw. Adding a WDH always reduces the required understeer. Such understeer ensures the tow vehicle automatically increases turning radius if cornering too fast. See pics below. Why travel trailers roll over.
Understeer and oversteer. Original pic – source unknown.
A heavy travel trailer‘s nose weight imposed on lighter tow vehicles is often more than its rear tires can withstand. This necessitates the use of a weight distributing hitch (WDH). These hitches are semi-flexible springy beams that, by using the tow vehicle’s rear axle as a pivot, shift part of that imposed weight to the front wheels. In doing so, however, removing that weight reduces the rear tires cornering power.
Major WDH maker Cequent (parent of Hayman Reese) advises restoring no more than 50% of the ‘lost’ front axle load. This usually results in the laden trailer’s nose being down by about five centimeters. Better by far, however, is to have a rig that has no need for a WDH. Doing so has long been routine in Europe.
Sway control systems
Any trailer towed via an overhung hitch has a natural tendency to sway. With well-designed and laden trailers towed by a suitable vehicle, such swaying normally dies out within two/three cycles. It is mildly annoying but harmless.
After-market sway control systems usefully and effectively control low-speed swaying. They introduce friction that dissipates sway energy as heat. That seemingly overlooked is a basic law of physics. That frictional force is a constant – but sway force increases with the square of the speed. At 100 km/h a friction hitch is close to useless. Its damping is down to 1% or so.
So-called dual cam systems ‘lock’ the travel trailer and tow vehicle together in a straight line. Normal cornering is enabled by tire distortion. The cams release for tight cornering, but also when sway forces are excessive and that control is most needed.
Both are effective at low speed. But, if fitted to a trailer that is otherwise unstable, these devices mask a dangerous underlying condition. They are akin to pain killers instead of medical treatment. Sway control is routinely included with some UK/EU travel trailers – but only as an aid to low-speed comfort.
Electronic stability control
Europe’s IDC, and AL-KO ESC activate when travel trailer sway exceeds about 0.4 g (an uncomfortable level). Or four repeated at about 0.2 g. They then automatically apply travel trailer braking. The Al-KO does so for one to three seconds at 75% of full braking. This reduces the sway, and particularly, reduces speed below the critical level. They can only be fitted to trailers that use the maker’s respective brakes.
How the AL-KO system works
The US products (from ALKO/Dexter) operate at lower levels of sway acceleration (about 0.2 g). They brake each travel trailer wheel at whatever level is deemed optimum. The makers claim they can be fitted to trailers with any form of braking. Either system is worth fitting. They do not, however, substitute for making stable travel trailers. When these systems are triggered they do not initially reduce sway. They reduce speed.
If using such systems never engage cruise control. That attempts to accelerate the rig to its preset (and previous) speed.
Manufacturers stress that such products cannot overcome the laws of physics. With that presumably in mind, most test them at under 100 km/h (about 60 mph).
The tow vehicle
For truly making stable travel trailers the tow vehicle must be heavier than the trailer. The more so the better.
Recommendations about trailer/tow vehicle weight stable stem from the 1930s. Travel trailers back then had an interior length of 4-5 metres. They weighed about 1000 kg (2200 lb). Most were towed by cars heavier than that 1000 kg (2200 lb). Few exceeded 80 km/h (about 50 mph).
Most EU/UK travel trailer bodies now recommend laden trailer weight should not exceed 85% of the tow vehicle’s unladen weight. They suggest that experienced owners may go up to 100% of the car’s unladen weight. Germany legislates that such trailers may not exceed 0.8 times the tow vehicle’s unladen weight.
Whilst the UK’s and European towing legislation has been updated, Australia’s has not. It relates only to maximums. A review is long overdue. The Caravan Council of Australia suggests that ‘for added safety and peace of mind’, the laden travel trailer should not exceed about 77% of the laden weight of the tow vehicle. That recommended 77% is less stringent than that of the UK and Germany – where towing speed limits are 20 km/h lower. Despite that, this recommendation was greeted by travel trailer-owner and industry rage. See Caravan Council of Australia. Few Australian travel trailer tow vehicle combinations meet these independent recommendations.
It is also becoming necessary to stress that limiting travel trailer length is even more important than weight.
Whilst environmentally unsound, when making stable travel trailers, for any over 2200 kg (4850 lb) laden, or over 6 or so metres, buy the heaviest tow vehicle you can find. See below for the minimal hitch overhang.
Braking and accelerating
A major towing risk is driving fast down a hill that has bends or changes in road camber. Particularly if braking, gravitational forces at the rear of a swaying trailer increase that sway. This is a particular risk on long winding motorway downgrades. And even more so in strong side winds. This mainly affects end-heavy trailers. To reduce risk, keep the speed below 70 km/h. Never brake (the tow vehicle) hard when descending a hill. It may cause the trailer to sway.
Advice on forums is that accelerating corrects sway. Whilst true – it is safe only at low speed. Accelerating whilst swaying at higher speeds may cause the rig to exceed the critical speed at which sway suddenly escalates. In that event jack-knifing is likely. If your system permits, a safer way is by gently braking the travel trailer alone.
The effect of speed
Any given combination of the tow vehicle and travel trailer has a unique critical speed. Above that speed, any sufficiently strong disturbing force may trigger it into non-recoverable jack-knifing. This typically results in the rig overturning.
That critical speed is determined by a number of factors. Tests in the UK show that optimally locating typical personal effects alone, can affect it by as much as 25 km/h. See Travel trailer and Tow Vehicle Dynamics for a full technical explanation.
In Australia is that (excepting WA’s limit of 100 km/h) travel trailers under 4.5 tonne can legally be towed at up to 110 km/h. This is a speed limit, however. It is not a ‘recommended’ speed. Many drivers resent being held up by slow traveling vehicles. Towing a trailer that is heavier than the tow vehicle at speed, however, is risky. An emergency swerve, or strong side gust can trigger irreversible snaking. Most owners never experience this. But some do.
Making stable travel trailers – various aids
There is no stability benefit in having dual axles unless travel trailer weight demands. If anything the opposite is so – they add weight and (worse) length.
Follow European practice by not carrying anything heavy on the A-frame. Locate gas bottles (if used) in a ventilated centrally located locker – or as close to the axles as possible.
When designing a travel trailer, set the axle/s as far back as you can – yet maintaining a tow ball weight that the tow vehicle can realistically handle.
This well-balanced 1998 Phoenix’s set-back axles resulted in almost legendary stability. Pic: Caboolture Travel Trailer Repairs.
The side-wall area to the rear of the axle/s needs to be marginally greater than in front of the axle. This reduces sway caused by a side-wind gust and by long trucks passing, or passed, at speed. The 1990s Phoenix shown above has diagonally sloping walls at its front. This ensured the set-back axles did not result in excess side (frontal) area. It is still respected for its excellent stability.
How can I tell if my rig is unstable
No trailer pulled via an overhung hitch can ever be 100% stable. If the trailer sways, that automatically causes the tow vehicle to sway in the opposite manner. And vice versa. Nose mass and correct weight distribution assist to limit this. So does a tow vehicle much heavier than the trailer.
A rig is likely to be acceptably safe if minor sway automatically dies out (without driver correction) after two or three cycles. It is mildly uncomfortable but not necessarily dangerous. EU designed trailers often have sway damping as standard. But makers first ensure sway is addressed as described above.
Long end-heavy trailers with substantial nose mass typically feel ultra-stable on tow. That high nose mass reduces the effect of sway forces. Problems occur however if that trailer begins to yaw. Then, that very mass that normally keeps it so stable will overcome the tow vehicle’s ability to control it. The trailer will begin to fishtail, and this may cause the rig to jack-knife.
The most common statement made by the driver following such an incident is: ‘It always felt so stable up until then’.
Making trailers more stable – further information
This topic is far too big to cover fully in article form. For full details see Travel trailer and Tow Vehicle Dynamics
The UK article www.caravanchronicles.com/guides/understanding-the-dynamics-of-towing/ by Simon P Barlow. is a generally similar and very down-to-earth approach. It is accurate and eminently readable but relates mainly to the much lighter UK and EU travel trailers.
If you liked this article you will like my books! All are written in a similar manner. Why Caravans Roll Over – and how to prevent it covers stability issues in depth. So too does the Caravan & Motorhome Book. My other books are The Camper Trailer Book, Caravan & Motorhome Electrics, and Solar That Really Works! (for cabins and RVs). Solar Success relates to home and property solar.
Solar regulators with current shunts – how to fix misleading readings
by Collyn Rivers
Solar Regulators with Current Shunts
Pic: Plasmatronics
If connected incorrectly, solar regulators with current shunts can register twice your true solar input. This article explains why. Moreover, how you can fix it.
Some years ago a magazine article outlined a solution to a non-existent problem. The article claimed that Australia’s sun may produce excess output. Furthermore that it can overheat solar regulators. It quoted a Plasmatronics 20 amps regulator as indicating 36 amps. The solar array, however, was only 18 amps.
The article misrepresented that happening. It wrongly assumed 36 amps output was feasible. It also advised adding a fan to cool the regulator. In reality, that system’s actual 16-18 amps were registered twice. Once as it flowed through the solar regulator. Then again. It flowed through a current shunt. That shunt’s output also, was to that regulator.
Solar in areas close to a large expanse of water or sand may produce freak high voltages. This happens if direct irradiation is reflected back to light scattered clouds. Then down again. Solar voltage may thus briefly escalate. Their output current, however, is limited automatically.
Solar regulators likewise block excess current. That is necessary for small capacity lead-acid batteries. AGM and lithium batteries, however, accept high currents without harm.
RB Books advises you to use a cooling fan for a solar regulator in tropical areas where airflow is also limited. You do not need one otherwise.
Battery return connection
For solar regulators with inbuilt monitoring, battery positive and negative returns must be direct to that battery. If you include a current shunt, your battery return must bypass that shunt. Unless you do, the solar current is recorded twice. Details vary between regulators.
It is not feasible to show how to do this in article form. Full details, however, are in Solar That Really Works! (for cabins and RVs). Also in Solar Success (for home and property systems). Furthermore, in Caravan & Motorhome Electrics.
Our other books are the Caravan & Motorhome Book, the Camper Trailer Book. For information about the engineer/technical author please Click on Bio.
Australian RV and towing rules and regulations – a general guide
by Collyn Rivers
Australian RV and towing rules
The current (February 2018) Australian RV and towing rules and regulations are outlined here. There will be changes, but not until (a probable) 2024.
Travel trailers – including fifth wheel travel trailers, camper trailers, and their tow vehicles
Tare Mass (weight)
This is the total mass of the trailer when not carrying any load, but ready for service, with all fluid reservoirs (if fitted) filled to nominal capacity except for fuel (as say for a diesel heater), which shall be 10 litres only, and with all standard equipment and any options fitted. This includes any mass imposed onto the tow vehicle when coupled to the resting on a firm and flat surface. It includes one 9 litre LP gas bottle, but not its gas content. It does not include any water.
Tare Mass is not defined as its weight ‘ex-factory’. It may be that, but if any specified ‘options’ are subsequently fitted or provided prior to the owner taking delivery, they too are legally part of the Tare Mass. This should thus be included as Tare Mass on the compliance plate, but that cannot be relied upon. Always, accordingly, insist on the trailer being weighed in your presence on a certified weighbridge, prior to final payment. Take this seriously: there are many confirmed reports of declared Tare Mass being well below the actual weight at the time of delivery.
Aggregate Trailer Mass (ATM)
This is an obligatory rating set by the trailer maker. It is its maximum legally allowable laden weight when standing on a level surface. It includes the weight carried by the tow bar of the towing vehicle. For travel trailers and camper trailers, the ATM includes personal effects but there is no legally obligatory allowance – only an industry recommendation. That (in 2018) is 250 kg (550 lb) for single axle travel trailers and 330-450 kg for two-axle travel trailers. Custom-made travel trailers, however, usually have more and the amount desired should be pre-agreed and included in the purchase contract.
Pic: courtesy of caravanbuyersguide.com.au
Gross Vehicle Mass (GVM)
Applicable primarily to the tow vehicles is a manufacturer-set rating that must not be exceeded. It is the vehicle’s permitted maximum loaded mass – defined as its Tare Weight plus the load and specified by the vehicle manufacturer. If subsequently modified, it is that mass shown on a modification plate attached to the vehicle.
Gross Combination Mass (GCM)
This is a maximum permissible weight rating (specified by the tow vehicle maker). It is of the tow vehicle’s total laden mass, plus the laden mass of anything it may tow. The GCM rating is particularly a trap for buyers of dual-cab utes. Many such vehicles are promoted as having a towing capacity of 3500 kg, but as their GCM is typically around or under 6000 kg if towing that 3500 kg, this limits the tow vehicle’s laden weight to 2500 kg. Such a combination is unsafe.
Tow Ball Mass
There are no legal requirements, but general engineering consensus is that a typical Australian-made travel trailer needs about 10% of its full laden weight as tow ball mass. The typically lighter EU/UK products require 6%-7% of the fully laden weight. The typically shorter (about 4 metres) camper trailers require 5%-7% but more is not a problem. Fifth-wheel travel trailers too are not that critical: 10%-25% is fine.
Legal Maximum Towing Weights
In Australia, for tow vehicles under 4.5 tonne, the maximum laden trailer weight is (currently and legally) the lesser of that allowed by the tow vehicle, tow hitch, or the maximum trailer mass. This overrides earlier legislation limiting towed weight to 1.5 times the tow vehicle’s unladen weight. Many believe these limits are too high for current travel trailer weights and towing speeds: see https://solbsau.centrails.com/caravan-and-tow-vehicle-dynamics/
Trailer Dimensions – conventional trailers
Centre-axled trailers (legally known as ‘pig’ trailers) must not exceed 12.5 metres overall. The maximum distance from tow hitch to centre-line of the axle/s must not exceed 8.5 metres. The rear overhang must not exceed the lesser of 3.7 metres, or the length of the load-carrying area (or body) ahead of the rear overhang line.
Trailer Dimensions – fifth wheelers
The distance from the towing pivot point to the rear of the trailer must not exceed 12.3 metres. That from the towing pivot point to the rear over-hang line must not exceed 9.5 metres. The rear overhang must not exceed the lesser of 60% of the former dimension or 3.7 metres. The maximum forward projection must not exceed a 1.9-metre arc from the towing pivot. The pic below hopefully makes this clearer.
Maximum dimensions for a large fifth-wheel trailer
Compliance Plates
Australian RV and towing rules stipulate that travel trailers and camper trailers less than 4.5 tonnes must have a compliance plate (currently) self-certified by the manufacturer or importer. It confirms the vehicle complies with the Motor Vehicle Standards Act 1989. The plate must specifically show the manufacturer’s or importer’s name, trailer model, vehicle identification number (17-digit), date of manufacture and Aggregate Trailer Mass. It must also include this statement. ‘This trailer was manufactured to comply with the Motor Vehicle Standards Act 1989’.
All information on the compliance plate (and/or otherwise supplied) must be true and correct for that specific vehicle. It should reasonably be expected this information to be accurate but this cannot be taken for granted. Discrepancies related to declared mass occur because some makers produce only standard products. If the declared tare mass is that ex-factory (see above) it may not include dealer-supplied and installed optional extras. If this arises, contact your state or jurisdictions equivalent of NSW’s Department of Fair Trading if the discrepancy seriously prejudices the RV’s usability (measuring errors of a few kgs, however, are inevitable.
NOTE: The above-noted self-certification is likely to be changed under the new legislation. This will be notified when more information becomes available.
Tyre Placard
This too is legally required (section 20.1 of VSB1). It must include the manufacturer’s recommended tyre size, tyre load rating, speed rating, cold inflation pressures and either the statement: ‘the tyres fitted to this vehicle shall have a speed category not less than ‘L’ (120 km/h)’. Or if the recommended maximum vehicle operating speed is less than 120 km/h, ‘the tyres fitted to this vehicle shall have a speed category at least equal to the recommended maximum vehicle operating speed, i.e. ‘ . . . ‘km/h.’, where ‘…’ is the vehicle manufacturer’s recommended maximum vehicle operating speed. This data may be included in the Compliance plate or on a separate plate – that is in a ‘prominent position’.
RV and towing rules – light (powered) vehicles (under 4.5 tonne GVM)
These are covered under the Vehicle Standards Bulletin 14 National Code of Practice for Light Vehicle Construction and Modification. There are minor differences from state to state – covered in each state’s version of Vehicle Standards Bulletin 06 (VSB 06).
Tare Mass
Far simpler than for trailers, this is the mass of any vehicle likely to be converted or made as a campervan or motorhome. It applies to the vehicle when ready for service, unoccupied and unladen. It requires all fluid reservoirs to be filled to nominal capacity except for fuel (10 litres only). It includes all standard equipment and any options fitted.
Gross Vehicle Mass (GVM)
The GVM must include 68 kg for each of two front-seat occupants, plus, if the designated ‘Seating Capacity’ is five or more, 68 kg for a rear ‘Seat’ passenger. Apart from that, it must include a personal effects allowance of 60 kg for each of the first two sleeping berths, and 20 kg per berth thereafter. This ‘allowance’ applies to everything carried. This includes pets, goods, bedding, food, cooking utensils and luggage.
Manufacturers are obliged to provide only that amount. Most owners find that to be far too low. If you need more (and you will), specify by how much, and in writing, when ordering. If you do not, dealers and manufacturers are likely to insist it is ‘not their problem’.
If self-converting an existing vehicle to a campervan and motorhome (under 4500 kg [9920 lb]), see VSB 14. This provides nationally acceptable technical specifications to ensure the result complies with Australian Design Rules (ADRs), and the Australian Vehicle Standards Rules (AVSR). Compliance with VSB 14 helps to ensure the result satisfies the regulatory requirements.
Heavy vehicles (exceeding 4.5-tonne GVM)
The rules and regulations for large motorhomes/coach conversions are covered in the National Code of Practice for Heavy Vehicle Construction and Modification. The dimension and weight requirements are prescribed in the Heavy Vehicle (Mass, Dimension and Loading) National Regulation 201. Dimensional limits are in VSI No. 5.
Main dimensional limits are length (rigid trucks) 12.5 metres (coaches) 14.5 metres. Width must not exceed 2.5 metres except for lights, mirrors, reflectors, signalling devices etc. Exclusions are explicit: e.g., they do not extend to awnings etc. Maximum allowable height is 4.3 metres. Rear overhang must not exceed the lesser of 60% of the wheelbase or 3.7 metres. The maximum combination length (if towing a trailer) is 19 metres.
These are overall measurements; they specifically include bicycle racks, bull bars, toolboxes and spare wheels etc. The weight limits are complex and apply in all states. (www.legislation.qld.gov.au/LEGISLTN/CURRENT/H/HeavyVehMDLNR.pdf.)
Motor vehicles and trailers over 4.5-tonne rating have a Compliance Plate issued by the Federal Vehicle Safety Standard (VSS). It provides proof-of-compliance with the applicable Australian Design Rules following VSS’s engineering inspection and approval.
The main reference, Vehicle Standards Guide (VSG5) sets out the safety requirements. It summarises the most common modifications. It shows how they must be done to comply with the Heavy Vehicle National Law and other legislation and regulations. Some vehicles need certifying by an Approved Vehicle Examiner. It is advisable to consult an Examiner before starting work – especially if the GVM has to re-rated.
An excellent reference source is the Vehicle Standards Guide 5 (VSG-5) Converting a vehicle into a motorhome Revised June 2018.
Electrical
The legal requirements for 230 volts are set out in AS/NZS 3000:2007 and AS/NZS 3001:2018. These apply to 230 volts regardless of its source (e.g. solar or generator etc) even if there is no intent or provision for grid supply.
Most states require Electrical Certification but (for reasons unclear) Energy Safety Victoria declares RVs are not ‘electrical installations’ – but ‘appliances’. Therefore (it claims) they are exempt. It requires RVs to meet AS/NZS requirements re 230 volts but installation need not be done by licensed electricians. Nor is Electrical Certification required.
There are no legal requirements for an RV’s 12/24 volt dc wiring, excepting that relating to obligatory separation from 230-volt wiring (avoided if wished by using 230-volt cable for the 12/24 volt system). For vehicles over 4500 kg, however, all 12/24 volt dc wiring must accord with the Heavy Vehicle (Vehicle Standards) National Regulation, Schedule 2, Part 2. Section 17.
With minor exceptions, the above electrical requirements apply also to RVs used in New Zealand.
Solar
Solar must comply with AS/NZS 5033. If it does not exceed 60 volts DC or 35.4 volts AC, there is no requirement that it be done by a licensed electrician. RV Books recommends using a nominally 12 or 24-volt system for RV use.
LP gas
LP gas installations (Australia-wide) must meet the requirements of AS/NZS 5601.2:2013 in detail. In addition, some states/territories have marginally different requirements. The only way to ensure compliance is to obtain the certificate from a licensed gas fitter. For imports see: https://solbsau.centrails.com/imported-rvs/
RV construction
Apart from chassis and related issues, there is no current RV industry ‘standard’ for any aspect of travel trailer or motorhome construction. This varies from excellent to cynically dreadful. A few companies nevertheless have established a good reputation. Travel trailer forums provide advice – but some posts are blatantly promotional.
Obligatory on-road lighting etc
Vehicle lights and reflectors must meet legal requirements relating particularly to specific functions. Requirements relate, for example, to defined viewing angles (horizontally and vertically) and lighting intensities. Those approved for RVs in Australia carry an E-mark or a CRN. The E-mark is a capital ‘E’, with a circled sub-script number plus an embossed approval number. Those sold only in Australia must have a CRN (component registration number).
Hints for home building
Weigh the bare vehicle prior to starting work. Then weigh and keep a running total of everything you include. It is very easy to underestimate the total weight. If the RV has a toilet or shower, it must be in working order when you present it for registration. If it is not, leave the space, as ‘that’s where I am going to add a cupboard’. (Hint: that ‘cupboard’ does not need to be in place for rego purposes.)
Every aspect of building an RV is covered in the Caravan & Motorhome Book. For solar and electrics see Caravan & Motorhome Electrics. For in-depth coverage of solar in RVs see Solar That Really Works!
Driving licence requirements
A C class licence is required for vehicles under 4.5 tonne (including with seating for up to 12 adults). Such licence includes towing a travel trailer as long as the GCM is not exceeded. (This now includes the ACT). An LR licence is needed for vehicles exceeding 4.5 tonnes and less than 8 tonnes. An MR or HR licence is needed thereon. This requirement relates to the potential carrying capacity. If the GVM is 5.5 tonne but has an on-road weight of only 4.4 tonnes you still need an LR licence.
Parking issues
In most parts of Australia, it is illegal to park a vehicle of 4.5 tonnes or more in built-up areas for over one hour. This applies also to a tow vehicle and trailer over 7.5 metres. An exception, however, is where a sign or traffic control device allows otherwise. It is legal to do so for dropping off or picking up goods but for no longer than necessary. If longer is needed, ask the local council to grant an exemption.
References
Australian RV and towing rules and regulations for large motorhomes/coach conversions are covered in the National Code of Practice for Heavy Vehicle Construction and Modification. Dimension and weight requirements are prescribed in the Heavy Vehicle (Mass, Dimension and Loading) National Regulation https://www.nhvr.gov.au/files/201402-0113-general-dimension-requirements.pdf.
Further information about AVEs and heavy vehicle modifications can be found at https://www.nhvr.gov.au/safety-accreditation-compliance/vehicle-standards-and-modifications/heavy-vehicle-modifications.
See also https://solbsau.centrails.com/articles/ and https://solbsau.centrails.com/imported-rvs/
See also the associated caravan-and-motor-home-compliance/
Our more technically in depth books are the Caravan & Motorhome Book, the Camper Trailer Book, Caravan & Motorhome Electrics, Solar That Really Works! for RVs and Solar Success for home & property systems. All are available from all main bookshops throughout Australia and New Zealand.
To assist others please Link to, or mention this article on related forum issues.
Australian RV and Towing Rules and Regulations – references
Australian Design Rules (ADRs) – https://www.infrastructure.gov.au/infrastructure-transport-vehicles/vehicles/vehicle-design-regulation/australian-design-rules
Heavy Vehicle National Law, Heavy Vehicle (Vehicle Standards) National Regulation, Heavy Vehicle (Mass, Dimension and Loading) National Regulation – www.nhvr.gov.au/hvmodifications
Vehicle Standards Bulletins(VSBs) – https://www.infrastructure.gov.au/infrastructure-transport-vehicles/vehicles/vehicle-design-regulation/rvs/bulletins
Further information
https://solbsau.centrails.com/caravan-and-tow-vehicle-dynamics
https://solbsau.centrails.com/articles
For issues relating to imported RVs see https://solbsau.centrails.com/imported-rvs/
For issues relating to imported RV electrics (particularly compliance) see https://solbsau.centrails.com/imported-rvs/
See also the associated https://solbsau.centrails.com/caravan-and-motor-home-compliance/
Virtually every issue relating to RV is covered in Caravan & Motorhome Book. Full details of RV electrical requirements, installation are in Caravan & Motorhome Electrics. Solar books are: Solar That Really Works! (for RVs) and Solar Success for home & property systems. For information about the author – click on Bio.
To assist others please Link to, or mention this article on related forum issues.
Travel trailer and tow vehicle dynamics
by Collyn Rivers
Travel trailer and tow vehicle dynamics
The complex interactions of travel trailer and tow vehicle dynamics are described here by Collyn Rivers. It is a precis of the rvbooks.com Why Caravans Roll Over – and how to prevent it.
In the early 1900s, trailers with central axles, towed by trucks with overhung hitches, were unstable. This escalated as towing speeds increased. Around 1920, Fruehauf (USA) realised hitch overhang caused (not just allowed) trailers to yaw anti-clockwise. And vice versa. Furthermore, the longer the hitch overhangs the greater extent of and the lower the road of its onset.
To this day, this is an inherent problem with conventional travel trailers. In the 1970s studies plus practical testing revealed the causes. These include excess trailer length, inadequate nose weight, poor weight distribution and incorrect axle positioning. Tow vehicle tyre pressure and side-wall stiffness too affect stability. Furthermore, such causes interact.
It was initially believed that excess trailer weight relative to the towing vehicle was the major concern. It is, however, increasingly realised that excess travel trailer length (and excess speed) are more the cause.
An otherwise stable vehicle towing an equally stable travel trailer will normally stay in a straight line. A side wind gust, however, may deflect it.
Acceleration relates to change in a mass’s rate of movement. It may be positive (e.g. increasing speed). Or negative (e.g. when braking). It is measured by dividing velocity (metres per second) by seconds. The unit is often shown as ‘G’ (but correctly as ‘g’). A driver cornering at an advised road sign speed will experience about 2 g.
Travel trailer and tow vehicle dynamics – tyre behaviour
Horse-drawn carriages had pivoted front axles. This ensures their wheels aligned with the pulling force. But if cornered too fast, the carriage’s inertia overwhelmed the horse’s grip. They would lose control. The carriage’s momentum, however, would cause it to keep moving. Then often overturn.
Tyres back then had to revolve, but not sink nor fail under load. Their marginal grip only partly resisted sliding. Braking was by ordering the horses to slow down. Also levering against a tyre to prevent it rolling. The main forces: for traction, steering and slowing, were external, via animal power.
A powered vehicle has similar limitations, but with a major difference. Forces for moving, braking and steering are applied and reacted only by its tyres.
A travel trailer’s tow vehicle acts physically much as those horses. The travel trailer depends on the stability of whatever pulls it – as did horse-drawn carriages. This is often overlooked.
Early pneumatic tyres
The pneumatic tyres used on early cars were like oversized-bicycle tyres (and solid tyres). They rolled more or less where pointed. When forces exceeded their grip, such tyres slid progressively and predictably.
Then cars became heavier and faster. Tyres became balloon-like. Owners sought a softer ride. Doing so, however, caused them to handle poorly. And often unpredictably.
By the mid-1930s it was understood how suspension and tyre interaction dictates handling. This particularly applies to travel trailers and tow vehicles. Their ultimate behaviour is dictated by their suspension and tyres. Not all travel trailer makers and travel trailereers know this. Let alone how.
Tyre basics
An inflated tyre does not roll over a surface. It has a caterpillar-like action. It lays down and picks up an elongated oval of tread (called its footprint). That footprint’s stability is determined by tyre construction and air pressure.
A typical tow vehicle tyre (green) increases ‘cornering power’ as its slip angle increases. It then levels off and starts falling away sharply. The latter introduces major and possibly terminal oversteer. It can result in jack-knifing.
Slip angles
Steering a tyre is like twisting a rolling balloon. Torque is applied, via the wheels’ rims, to the tyres’ sidewalls. The sidewalls flex, and via their stiffness and air pressure, cause the footprint to distort as directionally required. That footprint’s grip is partly molecular and partly frictional.
The steered footprint’s distortion creates an angular difference between where wheels point and the vehicle travels. That angular difference is called ‘slip angle’. The greater the tyre width, sidewall and tread stability and tyre pressure, the lesser the slip angle.
![[cara_up] and tow vehicle dynamics - electric vehicle batteries,book on batteries,electric car batteries,lithium ion batteries for electric cars,electric car battery technology,how long do electric car batteries last,electric vehicle battery life](https://solbsau.centrails.com/wp-content/uploads/2014/10/tyres-slip_angle3.jpg "[cara_up] and tow vehicle dynamics 76")
A typical tow vehicle tyre (green) increases ‘cornering power’ as its slip angle increases. It then levels off and starts falling away sharply. The latter introduces major and possibly terminal oversteer. It can result in jack-knifing.
The term slip angle can mislead. In normal driving, the footprint does not slip. That footprint is caused (by torque applied to the tyre’s sidewalls), to stretch and distort. It is only when side forces overcome footprint grip that tyre slides.
Footprint grip is not linear with imposed weight. When cornering, weight, (or any weightless downforce such as that from the so-called ‘wind spoiler’ used at the rear of racing cars) imposed on tyres increases their cornering power. It does so, however, by only 0.8 or so of that increase in grip.
Interaction of tyre slip angles
Interacting front/rear tyre slip angles dictate vehicle handling. Passenger vehicles have front slip angles that normally exceed their rear slip angles. This effect, called understeer, causes vehicles to veer away from side-disturbing forces. (So, likewise, do correctly-trimmed yachts, and aircraft).
If cornered too fast, an understeering vehicle automatically increases its turning radius. This reduces side forces, and hence slip angles. If, however, rear slip angles exceed front slip angles, the vehicle adopts an ever-tightening spiral. This causes its rear slip angles constantly to increase. Unless the driver applies some opposite steering lock, the rear slip angles increase until their footprints lose control. The vehicle then jack-knifes or spins.
Understeer and oversteer in extreme. In mild form, understeer adds stability. If the vehicle is corned too fast, it automatically adopts a wider radius turn, thus reducing undesired forces. Too much understeer, however, can result in the (upper) example above. The above is from www.driversdomainuk.com/img/oversteer.jpg (original source unknown).
Rear tyre distortion can cause oversteer. Such distortion can result from a yawing travel trailer. It imposes side forces on the tow vehicle’s rear. Other oversteer causes are excess tow ball weight, or too low tow vehicle rear tyre pressures.
Neutral steer may seem desirable. It is not. Neutral steer requires constant steering correction to overcome road camber. It causes a vehicle to be demanding and tiring to drive. Neutral steering is also impossible to maintain. Even minor changes in tyre pressure, loading, or road camber will cause understeer or oversteer.
Travel trailer and tow vehicle dynamics – maintaining footprint balance
A rig’s dynamic behaviour depends ultimately on tow vehicle tyre behaviour. This necessitates its tyres firmly gripping the road. Despite this, some trailer makers maintain that leaf-sprung products do not need shock absorbers. They argue that inter-leaf friction provides adequate damping.
Such damping, however, only acts as the spring’s compresses. On the rebound, however, the spring leaves are no longer held in firm sliding contact. As a result, release their rebound energy instantly. That energy jack-hammers the wheel back down. As the wheel impacts the ground it imposes shearing forces on wheel studs and stub axles. This causes those studs to snap. Stub axles break. Wheel bearings needing ongoing replacing. See Wheels Falling off Trailers
Inadequate or non-existent spring damping also prejudice electronic stability systems. These rely totally on travel trailer braking. Brakes, however, are only effective when tyres are firmly on the ground. Without adequate spring damping, they are not.
Travel trailer and tow vehicle dynamics – slip angles and load/tyre pressure etc
A tyre’s cornering power decreases with load and increases with tyre pressure. Adding tow ball mass necessitates increasing (tow vehicle) rear tyre pressures to retain the required slip angles. Those rear tyres need to be 50-70 kPa (7-10 psi) higher when towing. Never increase tow vehicle front tyre pressure.
If a vehicle’s front/rear weight balance is unchanged, it’s front and rear slip angles increase proportionally while cornering. The vehicle’s balance is maintained. But if its rear tyres loading only increases (as when a travel trailer yaws), front/rear slip angles change accordingly. If that induces oversteer, the rear tyre footprint may lose all grip. If that happens the rig is instantly triggered into a rig jack-knifing sequence.
Adverse effects of tow vehicle suspension changes
The relative tyre loading front/rear (and hence slip angles) is not just a function of weight distribution. It depends on how the suspension resists roll.
Never stiffen rear suspension without stiffening the front proportionally. Stiffening the rear alone causes more of the vehicle’s resistance to roll to be borne by its outer rear tyre whilst cornering. That increases its slip angle. If that footprint collapses or slides jack-knifing is likely. This is not just theory. It happens.
Minor spring rate changes are rarely detectable in normal driving. This is why many claim it’s safe. But by stiffening rear springing alone a strong yaw force can trigger that vehicle into sudden and terminal oversteer.
If a vehicle’s suspension needs upgrading it’s being overloaded. Suspension changes require serious expertise. Not buying airbags on eBay.
Travel trailer and tow vehicle dynamics – tow ball weight
To keep a travel trailer straight, front end weight is essential. That in Australia has long since been taken as 10% of gross trailer weight. Now (2020) many have as little as 4%. The British, whose travel trailers are 40% lighter (per metre) opt for 6-7%. Americans may use as high as 14%.
Basing a trailer’s tow ball weight on a percentage of travel trailer weight has long been routine. What matters far more, however, is a travel trailer’s length. Furthermore, where mass is distributed along that length. Because of this, even 10% may be too low for a long end-heavy travel trailer. This is an ever-increasing problem. Vehicle makers continue to reduce tow ball weight limits. And tow vehicle weight decreases.
Australian-made travel trailers typically need 250-350 kg nose weight. Such weight, however, thrusts the tow vehicle’s rear downward. As with pushing down on the handles of a wheel-barrow, that nose weight causes the vehicle’s front to lift. This undesirably shifts weight from the tow vehicle’s front (steering) tyres.
Weight distributing hitches
Developed initially in Australia (in 1950, but adopted almost immediately in the USA) a weight distributing hitch (WDH) forms a semi-flexible springy beam between tow vehicle and trailer. This reduces the weight otherwise imposed on the tow vehicle’s rear tyres. It also restores some of the otherwise reduced weight on its front tyres.
A WDH, however, only counteracts downforces on the tow vehicle’s rear tyres. Although the downforces on those rear tyres are reduced by the WDH, those tyres are still carrying much of the tow ball mass. They must still resist travel trailer yaw forces, but a WDH cannot reduce those yaw forces.
Weight distributing hitch drawbacks
That not realised by almost all travel trailer owners and makers is that a WDH inherently reduces a rig’s ultimate cornering ability, typically by about 25%. This issue is recognised and addressed by the US Society of Automobile Engineers in its current SAE J2807 recommendations. These recommendations are now followed by all US (and the top three) Japanese vehicle makers.
That (SAE J2807) recommendation includes advising to adjusting a WDH to correct no more than 50% of the tow vehicle’s rear end droop. Never the full amount. It suggests correcting 25% of that rear end droop is better. Such advice has long been given by Cequent in the USA. (Cequent owns Hayman Reese). Hayman Reese locally used historically to advise levelling the rig. It now follows the Cequent (USA) advice.
A WDH is only required when the download on the tow vehicle’s rear tyres is not acceptable. If it is acceptable you can readily compensate for that weight shift. To do so, increase tow vehicle rear tyre pressures by 50-70 kPa (7-10 psi).
Travel trailer independent suspension has next to no benefit
Passenger car independent (front) suspension stems from the 1930s. It resulted from a buyer demand for softer suspension. Softening and increasing spring travel, however, resulted in beam front axle wheel ‘tramping’. The wheels would alternately jump up and down and swing violently from lock to lock. This particularly happened with poorly damped and/or soft suspension long-travel suspension.
Around 1934, General Motor’s Maurice Olley established this was a ‘gyroscopic precession’. You can experience this by holding a bicycle’s front wheel off the ground, spinning it and then swinging it in an arc. It imposes an unexpected swaying effect. This can also be shown via a gyroscope.
Here, (US) teacher Gary Rustwick demonstrates the effects of gyroscopic precession. He swings the spinning wheel in an arc whilst standing on a free-moving turntable. As he does so precession forces cause the turntable to rotate.
Wheel precession is dangerous. If it builds up, the vehicle becomes unsteerable. Worse, reducing speed (as one must) decreases the tramping frequency but increases the amplitude.
Need for steered wheel stability
In the early 1930s, General Motors’ Maurice Olley realised precession was only totally preventable by ensuring steerable wheels rose and fell vertically. Not forced to move in an arc created by a tilting beam axle. Achieving this required steered wheels to be suspended independently.
This concept was not new. It was used on a road-going steam locomotive in the late 1800s. Lanchester used it in 1901, Morgan in 1911, Lancia and Dubonnet in the 1920s. But all did so to reduce unsprung mass and improve the ride. Olley knew that too. He particularly knew that independent (and vertical) front wheel travel was vital for soft suspension.
Non-steerable wheels are subject to the same forces. As they cannot swivel, however, such forces do not matter. This is why many cars and most trucks and 4WDs retain beam-axle rear suspension.
Travel trailer wheels do not steer
As travel trailer‘s wheels do not steer there is no need or benefit for independent suspension. Nor is there any need for suspension travel greater than that of their tow vehicles. For much of the time, a travel trailer rocks on an axis around its tow hitch. Many pointlessly have suspension like the wallowing US cars of the mid-1930s. Almost all currently-made cars are much firmer. They also have less suspension travel. And do not wallow.
Suspension issues
Human physiology dictates passenger vehicle suspension. The result is compromised by the brain’s response. Nausea is created if the suspension is too soft, and discomfort if too hard. Such constraints do not apply to non-human carrying trailers.
Travel trailers do not carry passengers. It is absurd for their makers to base the suspension on huge wallowing Chevrolets of the mid-1930s. For optimum road holding, suspension needs to be firmer. This can readily be done and with no risk to any contents.
Travel trailer and tow vehicle dynamics – fifth wheel travel trailers more stable
A fifth wheel travel trailer pivots from a hitch above the tow vehicle’s rear axle/s. Side-wind gusts may cause the trailer to swing slightly, but the forces are low and quickly self-damp. They do not affect the tow vehicle. Drivers are rarely aware of them. As long as a fifth wheeler’s rear wheels are well back, the weight on the tow vehicle is within that vehicles’ limits. A well-balanced fifth wheeler is stable at any speed.
Action and reaction
As described earlier in this article a hitch distanced behind a tow vehicle’s causes a trailer to yaw if that tow vehicle yaws – and vice versa. This would not overly matter if the trailer yawed in the same direction. That overhung hitch, however, causes the opposite. If the tow vehicle yaws clockwise, its overhung tow ball yaws anticlockwise. As it does, it takes the nose of the travel trailer with it.
Likewise, if the travel trailer yaws clockwise, that overhung tow ball swings the rear of the tow vehicle anticlockwise. This is the root cause of conventional travel trailer instability. The longer that overhang, the greater the (undesirable) effect.
At low levels, yaw interaction is mainly annoying. It is reducible (at low speed) by friction and other forms of damping. It typically dies out after two or three cycles. If it does not, it indicates instability. That needs resolving at its source. Friction damping is almost useless at speed. This is because the friction stays constant. Yaw forces, however, increase with the square of the rig’s speed.
Severe yaw is serious
If severe yawing occurs above a critical speed (specific to each rig and its loading) the yaw may self- trigger into jack-knifing. It is fuelled by the rig’s kinetic energy. Once triggered, if travelling at speed, this sequence is almost impossible for a driver to correct.
Musicians and public speakers experience a similar effect. If their microphone picks up the sound from the loudspeakers, that sound suddenly develops a full-on yowl. This is only stopped by drastically reducing the volume (akin to braking a travel trailer). Or by moving back from the loudspeakers (akin to reducing tow hitch overhang).
A conventional travel trailer and tow vehicle are inherently unstable. A sanely designed, laden and driven rig is nevertheless safe as long as the speed is not excessive for that rig.
Critical speed
Depending also on loading, every combination of tow vehicle and travel trailer has a so-called critical speed. Once above that speed, yawing can irreversibly escalate out of driver control.
That critical speed, and the degree of yaw, is directly associated with the tow vehicle’s mass relative to the travel trailer’s mass (and particularly mass distribution). It is also associated with travel trailer length, hitch overhang, tyre type and size, sidewall stiffness and pressure etc.
All of the above (and more) is involved. The longer and the lighter the tow vehicle (and its tow ball mass) the lower that critical speed. The onset of critical behaviour is sudden. Because of this, the still-common suggestion ‘accelerate to dampen yawing’ is risky except at low speed.
The critical speed effect does not imply that the rig jack-knifes if that speed is exceeded. If, however, a rig is travelling at or above its critical speed, a strong side wind gust, or a strong swerve puts it at risk. Few owners encounter this, so many dismiss its possibility.
A demonstration of the effect of excess rear end mass can be seen at: www.towingstabilitystudies.co.uk/stability-studies-simulator.php
Avoiding jack-knifing
When a travel trailer yaws, it transfers the yaw force via an overhung hitch to the tow vehicle. The transmitted forces are resisted by the tow vehicle’s weight and the grip of its tyres. Minor travel trailer braking assists straightening the rig. Heavy travel trailer braking, however, may overwhelm the travel trailer’s tyres as they are already stressed by yaw forces.
If the travel trailer yaws never apply tow vehicle braking. Doing so may trigger that tow vehicle’s already stressed rear tyres into terminal oversteer. It may cause it to spin.
Beware of cruise control
Cruise control detects the minor drop in speed when yawing occurs. It attempts to restore the set speed. Meanwhile, the tow vehicles tyres heat up and slip angles increase. While convenient, it is better not to use cruise control when towing a heavy rig at speed.
Wind effects
A further cause of major travel trailer instability is wind forces from fast-moving trucks. This is particularly so of those towing trailers. And even more so if the truck has a flat front (rather than a bonnet). That bluff front creates an ongoing strong bow wave plus a vortex (i.e. a rotating wind gust) along its side.
If overtaking (or being overtaken) a tow vehicle and travel trailer will experiences wind buffeting. As the travel trailer‘s tow vehicle approaches the rear of the truck cab, a side wind vortex initially causes the tow vehicle to be drawn toward the truck. As the tow vehicle draws closer to the front of the truck cab it is hit by the truck’s strong side-going bow wave. This causes the travel trailer to swing slightly away from the truck. The overhung hitch causes the front of the travel trailer to sway toward the truck. A vortex pulls it in further. This initiates a rapidly developing yaw cycle. Jack-knifing can result.
A generally similar but less common effect occurs when the truck and the travel trailer rig are approaching each other at speed on narrow roads.
Electronic stability systems
Electronic stability systems monitor travel trailer yaw. AL-KO’s applies travel trailer braking when it detects ongoing yaw forces exceeding about 0.2 g. The maker warns the system is an emergency aid. It is intended to prevent accidents. It does not enhance stability.
The Dexter system applies the travel trailer’s brakes asymmetrically (i.e. out of phase with the yaw). It does so at lower yaw acceleration levels. As testing is done at 60 mph (just under 100 km/h) the ability (except as a yaw reducer) to prevent a catastrophic incident at speeds above the critical speed is unknown. Both Dexter and AL-KO (now one company) emphasise their products cannot override the laws of physics.
Enhancing rig stability
The major factors include everything that affects front/rear tyre slip angles. Those within owner control include:
Loading and load distribution of the travel trailer and tow vehicle.
Excess tow ball overhang caused by unnecessary hitch bar extension.
The speed at which the rig is driven.
Fitting and use of yaw control devices, WDHs etc.
Those outside direct owner control (but subject to the choice of rig) include:
Length of the travel trailer, the unladen weight of the travel trailer.
Weight and stability of the tow vehicle.
Those determined by the travel trailer builder include:
Length of the travel trailer.
Weight of the travel trailer.
Distance from travel trailer tow hitch to axle centre/s.
Distribution of weight along the length of the travel trailer (particularly at its rear).
Centre of mass (i.e. weight) in both planes.
Height of the roll centre and roll axis (as imposed by the geometry of the travel trailer’s suspension).
Moment Arms about the roll axis, particularly at the far rear.
The magnitude of yaw inertia.
The radius of gyration.
Damping of yaw and roll.
Tyres with good sidewall stability (such as light truck tyres).
Optimising towing stability (summary)
Tow vehicle behaviour is now well understood and proven. That required is a long-wheelbase vehicle with a short rear overhang that weighs at least as much as the trailer. Towing three or more tonne behind a 2.5 tonne dual-cab ute is an accident awaiting the circumstances to trigger it.
A major undesirable factor with travel trailers is excess length. Excess weight matters, but excess length is now known to be a far greater issue.
Reducing travel trailer perimeter weight, and particularly rear-end weight, is vital. If feasible house a travel trailer spare wheel below the chassis and in front of or just behind the axle. Batteries are best located centrally between the axles. Water tanks should be wide but not long and located as centrally as possible.
Friction devices smooth low speed snaking, but have a negligible effect at high speed. One that works well at low/medium speeds is likely to be less than 1% effective at 100 km/h (62 mph). Elastic energy held within sprung-cam devices may suddenly be released when such devices are overwhelmed – and ‘fed into the system’.
Lateral sidewall stiffness of all tyres assists.
The major factor, however, is excess speed.
Travel trailer and tow vehicle dynamics – driver reaction
Most big rigs feel stable in normal driving. There is also usually sufficient stability to enable an experienced driver to cope with scary but not accident-resulting situations.
A major issue is that (particularly) with heavy rigs, unless grossly unbalanced, it is not possible for a driver to know (by feel or ‘experience’) how that rig will behave in an emergency. Most big rigs feel ultra-stable. Short vans are more stable but may feel twitchy (particularly if twin axle). The concern is how the rig behaves in situations that cause major yaw. These include sudden strong side wind gusts on a motorway, braking hard on a steep winding hill at speed, and swerving at speed.
‘My rig always seemed so stable’
Police say the most after-accident reaction is: ‘my rig always seemed so stable until it suddenly jack-knifed’. Such apparent stability is typical of container ships and car ferries, until a rogue wave or turning too sharply proves otherwise.
There is increasing evidence that the safe maximum speed for big rigs is under 100 km/h. This is related to tow ball weight. Furthermore, the lower that weight, the lower the safe speed.
Summary
The above is a precis of some of the most relevant parts of RV Books’ Why Caravans Roll Over – and how to prevent it. The book is written in plain English but has a fully referenced final technical section.
Acknowledgement
My articles in this area primarily summarise current thinking. They stem from my interest and involvement while employed by Vauxhall/Bedford’s Research Dept in the 1950s, and particularly by the influence of Maurice Olley.
Maurice Olley was born in Yorkshire in the late-1800s. Following time as Rolls-Royce’s Chief Engineer, he worked with General Motors Research Division. He later returned to Vauxhall Motors (UK). I was privileged to attend his lectures during my years at Vauxhall Motors Research Centre
His work lives on in the 620-page Chassis Design: Principles and Analysis. The book was prepared from Olley’s notes, some 27 years after his death by Milliken and Milliken.
Why the Move to Electric Vehicles
Why the Move to Electric Vehicles
Introduction to our ten part series on electric vehicles
Why the move to electric vehicles. It is largely because in the past few years there has become an increasing realisation that it is impossible to totally remove emissions from petrol engines. This applies even more so to diesel engines (although to their shame, major European car makers used fraudulent methods to cover this up). It is now all but certain that diesel cars and diesel 4WDs will cease being made after 2030. Many makers are planning an earlier date for diesel as it is becoming clear that it virtually impossible to remove the major polluting components.
As our associated article Electric Vehicle History shows, this is not so much a move to electric vehicles – but a return to them. Almost all cars in the USA were electric from the late 1800s until 1920 or so. They were rendered obsolete largely because battery technology was stagnant – and that of petrol engines was not. It is now virtually certain that about half of all cars will be electric by 2030, with the current part fossil-fuel/part electric hybrids being phased out as battery storage technology advances (to provide comparable range) and the recharge network becomes global.
There is also a strong possibility that we could see hydrogen used both as a fuel and for energy storage (it works well for both). Its only downside is that it is corrosive.
As the world seems to be increasingly taking climate change seriously the move to electric vehicles is accelerating. In July 2021, the European Commission proposed a 100 % reduction of emissions for new sales of cars and vans as of 2030. In 2021, General Motors announced plans to go fully electric by 2035. Volvo Cars announced that by 2030 it “intends to only sell fully electric cars and phase out any car in its global portfolio with an internal combustion engine, including hybrids.” It’s clear that the change is inevitable.
The Electric Vehicle Series
This is a part of a series of articles about the history and technology involved in electric vehicles.
Travel trailer and motorhome compliance
Travel trailer and Motorhome Compliance
Travel trailer and motorhome compliance can confuse. Imports are often not 100% compliant. This article shows what is required. Total travel trailer and motorhome compliance is rarely an issue with the locally-made product. It can be, however, with imported travel trailers. This was particularly so of fifth-wheel travel trailers. There can also be problems with private imports. Non-fully compliant units may legally be used, but only by the original buyer. That buyer often truly (but wrongly) believes them to be 100% compliant. They must not be sold, nor even given away unless brought to 100% compliance.
Travel trailer and Motorhome Compliance is written by the Caravan Council of Australia (CCA). It is published here with the CCA’s permission. It relates to RVs of all types. Similar requirements apply to boat-trailers and horse-floats. See also Imported RVs.
Note: This information is still (late 2020) mostly current but will change once the new Road Rules come into effect – probably in 2024.
Travel trailer and Motorhome Compliance
‘Is your camper trailer, travel trailer or motorhome fully compliant? Many are not, especially American fifth-wheeler and motorhomes imports.
‘It has been proven many times that declarations of compliance on many imports have been false. The Australian Federal Government even warned against this. In such cases, severe penalties can apply.
‘Many manufacturers, importers and ‘facilitators’ have been able to get away with this. When legal actions are instigated against them, or one of their vehicles is involved in an accident, serious repercussions inevitably occur. This is especially if they lead to a coroner’s enquiry. In such cases, lawyers and engineers dig deep to expose the truth.’
Motor vehicles & over 4.5 tonne trailers
‘A motor vehicle or a trailer over 4.5 tonnes will have a Compliance Plate. It is issued by the Federal Vehicle Safety Standards (VSS). The plate confirms the vehicle conforms with all applicable Design Rules. Also, that is been inspected and approved by VSS. That organisation will then probably inspect one of the subject vehicles. This is to confirm that the evidence accurately matches the vehicle’s description and specifications.
Travel trailers & trailers under 4.5 tonne.
‘Self-certification is currently (2020) permitted for travel trailers and trailers under 4.5 tonne ATM Rating. The manufacturer or importer provides a declaration on the VIN/ Trailer/Compliance Plate, that the vehicle complies with the Motor Vehicle Standards Act 1989.
‘Since that 1989 Act became legislated, all travel trailers and camper-trailers have been required to have a valid Trailer Plate securely affixed. As with motor vehicles, buyers and owners expect that all information on the Plate is true and correct. In many instances, this has not been the case.
Plate requirements
‘The Plate is legally required to show the following information:
- Manufacturer’s or Importer’s Name:
- Trailer Model:
- Vehicle Identification Number (17-digit):
- Date of Manufacture:
- Aggregate Trailer Mass Rating:
- The Certification Statement: ‘This trailer was manufactured to comply with the Motor Vehicle Standards Act 1989’
- Often the legally-required Tyre Placard is also included and possibly other information. Three of the items required on the Tyre Placard are: the manufacturer’s recommended tyre size: (without mentioning brand names)
- Tyre load rating
- Speed rating
- All information on the Plate, or otherwise supplied to the public, must be true and correct for that specific vehicle.
- In Australian Consumer Law became uniform legislation. The term ‘Merchantable quality’ later became up-graded to ‘Acceptable quality’. ‘Fit for purpose’ is the main consideration when issues arise. Honesty and ‘duty of care’ are also prime considerations.
VSB-1 (Vehicle Standards Bulletin No: 1) is the legal instrument that prescribes the legal requirements for travel trailers and trailers (under 4.5 tonne ATM Rating). This can be downloaded from https://www.infrastructure.gov.au/infrastructure-transport-vehicles/vehicles/vehicle-design-regulation/rvs/bulletins/vsb1
Ratings and masses
‘The biggest issue that leads to complaints and litigation is Ratings and Masses. This especially relates to the load-carrying capacity’ (maximum legal pay-load) of the vehicle.
Travel Trailer Ratings – reproduced by express permission of the Caravan Council of Australia.
The ‘Tare Mass’ is legally the measured (not estimated) mass of the vehicle as it leaves the factory. The water tanks and gas cylinders are empty. All equipment and accessories that were stated on the Purchase Contract must be included. Tare Mass is not legally required to be stated on the Plate. There is, however, a strong case for being a critical duty-of-care responsibility of the vendor.
ATM
‘The Aggregate Trailer Mass defines the maximum that the trailer may legally weigh on-road. The load-carrying capacity is thus the ATM Rating minus the Tare Mass. Many complaints relate to the actual Tare Mass being significantly more than is the stated Tare Mass. Problems have arisen because dealers or owners have added equipment and accessories later, without requiring the Tare Mass being up-dated.
It is al-but vital for buyers to weigh a newly-purchased travel trailer or camper-trailer (new or second-hand) – to confirm the actual Tare Mass, at a certified weigh-bridge. The (empty trailer’s) ball-loading should also be accurately measured.
GTM rating
‘The GTM Rating is the maximum weight of the fully-loaded trailer that may be imposed on the trailer’s axle when it is coupled to the tow vehicle. It is thus the ATM minus the mass carried by the tow ball. The GTM is not legally required to be stated on the Plate. Despite that, some ADRs (and unique state requirements) depend on the GTM Rating. This especially applies to braking requirements above and below 2000 kg (4400 lb) of the GTM Rating. The ratings of the wheels, tyres, axle(s) and suspension must all be equal to, or greater than, the GTM Rating. It is important to note that the GTM Rating has no bearing on the ball-loading.
Other important compliance items
- Ratings and method of attachment of the coupling and the safety chains
- Braking system
- Lamps and reflectors
- Electrical wiring between the vehicle and the tow-vehicle
- Vehicle dimensions… length, width, height, rear-overhang.
‘The most critical – and potentially lethal (if not correct) – internal safety items are the electrical and gas appliances and installations.
‘These must be in strict accordance with the appropriate Australian Standards. There have been a number of cases where appliances and installations – both electrical and gas – have not been approved to Australian requirements. Some states/territories may have different interpretations and requirements. The way to best ensure full compliance is to obtain certificates from licensed electricians and gas fitters.
‘Lights and reflectors have a number of legal requirements. Each has to be designed for its particular function: e.g. a generic red light cannot be used for the rear position, end-outline, and stoplights; different lamps and reflectors have different fields-of-view (horizontally and vertically) and different maximum and minimum light intensities.
Travel trailer and motorhome compliance – E-mark & CRN
‘There have been numerous cases of cheap non-compliant lights being used on travel trailers and camper-trailers offered for sale in Australia. Those approved have either an E-mark or a CRN (see below).
- An E-mark (E for Europe) is used on many vehicle components used internationally. The mark consists of a capital ‘E’, with a small sub-script number (inside a circle) and with the approval number embossed in the plastic. Lights and reflectors that are sold only in Australia, may have an E-mark. They are however required to have a CRN (Component Registration Number). This is issued by the VSS after proof-of-compliance is provided. Such lights and reflectors must have unique identification markings so that they can be cross-referenced to the specific CRN.
- Lights and reflectors must be oriented correctly, especially front and rear reflectors (in a side view). The prescribed number of lights and reflectors must be fitted, and they must be in the specified positions. While lights and reflectors may not be as critical as brakes, couplings and tyres, they are still an important road-safety item’.
Further information
Travel trailer and motorhome compliance is also covered in my articles: Imported RVs, Imported RV Electrics. It is also covered in my books Caravan & Motorhome Book, Caravan & Motorhome Electrics, and the Camper Trailer Book
The full list of requirements is at:
http://media.wix.com/ugd/74afe1_3005c62231b8dbb46ad5ce8efe57bce5
Wheels falling off trailers – and how to stop it happening
by Collyn Rivers
Wheels Falling Off Trailers
Wheels fall off trailers, their wheel studs break or wheel nuts loosen. Trailer wheel bearings need ongoing replacement. Stub axles may fracture. Next to none of this, however, occurs with the tow vehicles. Here is why it happens, and how to prevent it.
That fastenings such as wheel nuts may be caused, not just permitted, to loosen is rarely covered in engineering training. The causes and prevention are, however, known. This referenced article by Collyn Rivers explains how, why and how to prevent it.
Wheels falling off trailers – and fastenings work loose
The thread of a screw fastening must have some side clearance to enable the nut (or stud) to be turned. Tightening, however, causes the stud to stretch slightly. This marginally decreases its diameter, thus increasing inter-thread clearance. Inter-thread friction normally prevents or limits sideways movement between the threads. As the thread is spiral and in tension, momentarily relaxing the frictional contact may cause the fastening to ‘ratchet’ itself undone. Overtightening worsens this as it further decreases thread diameter – thereby increasing the interthread gap. Wheels fall off trailers because of this.
To see this happens, hold (by its head and pointing downwards) a large-diameter clean dry coarse-threaded bolt, with a loose nut. While stationary, the nut (restrained by minor inter-thread friction) stays where it is. If shaken from side to side, however, gravity will cause the nut to unwind. With a similar bolt and nut under tension, repetitive sideways movement above a certain force will likewise ‘ratchet’ that nut loose.
This can happen with wheel nuts or studs. As the wheels encounter bumps and pot-holes, shock loads impact the wheel studs. Unless correctly tightened or somehow restrained, the studs or nuts may work loose.
The stub axle sheered off this tour group’s trailer on the corrugated track road to the tip of Cape York. It had no shock absorbers, nor provision for fitting them. The OKA in the distance belonged to the author. Pic: Author.
Why wheels fall of trailers – but rarely off whatever tows them
Fastenings mainly loosen where there are repeated side shocks. It also occurs where bolted assemblies bend. etc. It happens particularly with wheel studs and nuts and is usually why wheels fall off.
Far more wheels fall off travel trailers and camper trailers than ever from cars. Wrecked trailers with wheels torn off, or stub axles broken, litter mainly corrugated outback tracks. It does not, however, affect all trailers. If you inspect them you will find that almost all not just lack shock absorbers – most lack provision for fitting them.
The effect of not having shock absorbers
A wheel encountering corrugation (etc) is thrust upward. This compresses the spring. Inter-leaf friction absorbs a small part of the impact on the upward movement. Most, however, remains (as elastic energy) in that spring. Once over the bump, the now unrestrained spring jackhammers the wheel and axle downward. The wheel strikes the road with huge force. The resultant shock load (proportional to the wheels and axle’s mass and the square of their velocity) is now taken via the unfortunate wheel studs.
This issue is at its worst on corrugated roads. These typically have about 1100 plus corrugations per kilometre: 1000 km of corrugation imparts over one million hammer-like blows. All via those studs. Once the stud or nut works even slightly loose. Impact forces may then shear the studs in half. Such repeated shock loads also wreck wheel bearings. Furthermore, they may eventually cause stub axles to break.
This rarely happens with tow vehicles. All have shock absorbers, and even if badly worn most retain at least some damping effect. Much as firing an arrow into water, shock absorbers absorb and dissipate energy. They convert much of the springs released elastic energy into heat. The vehicle tyres also dissipate such energy.
The omission of shock absorbers on trailers (and consequent problems) is confined mostly to Australia. The above is an ultra-cheap but well-engineered Finnish garden trailer that has such large shock absorbers as standard. Pic: rvbooks.com.au.
Friction shock absorbers were fitted to cars as early as 1905. They had them despite travelling at low speed and thus incurring far lower forces. If a trailer maker says shock absorbers are not needed, buy from somewhere else.
Some trailers but rarely travel trailers have springs so stiff there’s little movement to dampen. The springs may not break but the trailer contents take a beating. Furthermore, wheel studs and stub axles are more likely to shear.
Correctly tightening wheel studs and nuts
1. Clean threads thoroughly. Ensure nuts are free to spin along the stud’s full threaded length. Discard any that do not. Never use a nut or stud that is or has been corroded. Studs and nuts need to be totally clean and dry.
2. Locate the wheel on the studs. Finger-tighten using a diagonal sequence. Give the wheel a few wriggles to allow correct location.
3. Tighten diagonally and progressively.
4. Use a torque wrench for final tightening and only to vehicle maker’s specifications. Never exceed specified tightness. That ‘more is better’ is counter-productive – it stretches the thread, thereby reducing its diameter – and hence the gap between the threads.
5. Recheck after 50 km and a further 100 km. If further re-tightening is needed, whatever is being clamped is under-engineered and bending. This occurs with U-bolt axle clamping plates on early OKAs. Any such issue needs urgent fixing by an engineer. If really seeking a belt and braces approach, apply Loctite 290 after the final bedding down. See below re how it works.
If employing a tyre fitter, insist beforehand that a torque wrench be used for final tightening to the vehicle maker’s specification (most include that in the instruction manual).
Never allow anyone to use a rattle gun for this: the risk of serious risk over-tightening is high. Ideally, have a high-quality torque wrench and insist on doing the final tightening yourself.
Insist on the above. Many mechanics and tyre fitters believe they can ‘feel’ correct tension. Extensive research shows that few can do so. Tests (conducted by Vauxhall/Bedfords Research) show variations of plus/minus 30%..
Loctite – and similar products
If there is no inter-thread gap, no side movement is possible. There is hence little likelihood of such threaded fastenings undoing. Rather than ‘glueing’ threads together, Loctite (and similar products) thus expand. They fill the gap between threads. This specifically precludes sideways movement – that enables, or causes, undoing.
The specialised Loctite 290 product is designed for fastenings that subsequent re-tightening (e.g. wheel and U-bolt nuts). It is applied after the initial re-tightening period. It is a self-wicking fluid that works its way between even horizontal threads. As the product effectively precludes nut unwinding, further torque checks are (claimed to be) unnecessary. It must, however, be reapplied after wheel changes.
This product is also used to prevent catastrophic failures. It is thus used in aircraft, and also roller coasters. It even prevents jackhammers from falling apart.
Even without Loctite, in over 500,000 km and fifty years of mostly off-bitumen driving, I have yet to have a wheel nut even loosen. Let alone fall off. And that includes twice across Africa, and a now fourteen return trips across Australia from Sydney to Broome, mainly on corrugated dirt tracks via Alice Springs. All I do is to tighten, via a torque wrench, to the amount the vehicle maker advises. And use truly high-quality shock absorbers.
Rattle guns are prone to over tighten, thereby stretching the stud. This reduces its diameter, thus increasing inter-thread spacing. This alone causes studs to crack and/or sheer off. The fastener and automobile industries emphasise that wheel nuts and studs must never be finally tightened by rattle guns (impact wrenches). They insist that such tightening may only be done via a high-quality torque wrench. This wrench must have known accuracy. It must tighten to vehicle manufacturer’s specified amounts.
Recheck (and tighten if necessary) after 50-100 km. And again after 1000 km. But many tyre fitters sadly ‘know better’. They use only rattle guns.
If you use a lubricant (most authorities recommend against it) you must reduce tightening torque by about 20%. Do not use anti-seize materials, for any but totally static applications. Their intended role is easing undoing.
Caravan Council of Australia
Here’s what the Caravan Council of Australia says about it.
‘The CCA continually receives reports of broken wheel studs, and loose wheel nuts… sometimes with the nuts unwinding completely off the studs.
It must be stressed that if a stud breaks, it is certainly no proof that the stud itself was faulty. There are a number of reasons for the problems.
‘All supplied instructions regarding wheels and wheel nuts must be precisely followed.
‘It is vital to ensure that if ‘van owners or dealers fit after-market wheels and nuts, they thoroughly check to ensure the replacement wheels and nuts are, in fact, completely suitable for the vehicle and axles.
Possible Reasons for Broken Wheel Studs, or Loose – and Lost – Nuts:
- The pitch circle of the studs in the (imperial) hub not exactly the same as that of the holes in some (metric) wheels, such that all studs bend when the nuts are tightened
- The angle of the taper on the nuts not the same as the angle of taper in the wheels
- Low-Grade steel studs being used
- The hole in the wheel centre not compatible with the spigot diameter of the hub
- The serrated studs not “fully driven home” when pressed into the hubs, such that they gradually “give a little”, thus causing the nuts to become loose
- Rattle-guns – set at unknown high-torque levels – used to tighten wheel nuts (rather than just undo them), causing the studs to stretch, and thus become weakened
- Nuts being tightened in a circular pattern in one action, rather than in a criss-cross pattern, using two or three (increasing) torques
- Wheel centres being highly dished, thus acting as a large spring-washer that gradually loses its tension and causes the nuts to loosen.
Clearly, all nuts must be tightened to the correct torque, and in the correct pattern, in strict accordance with the instructions provided by the wheel or chassis manufacturer.
It is strongly recommended that pencil lines are made on one face of each nut – with a mating line on the wheel – so that a quick visual inspection can detect any loosening of a nut. Clip-on plastic “indicators” – fitted to each nut, with their adjacent “arrow-heads” aligned – provide an even-quicker warning of any nut loosening.
Continual vibrations – and occasional heavy impacts – from road surfaces, inevitably have an adverse effect on the wheel assemblies.
This is severely aggravated if the tyre pressures – and the spring rates – are too high for the actual wheel-loading.
Stresses on the wheel assemblies are further increased if shock-absorbers (dampers) are not fitted.
Leaf-springs do provide some damping of vibrations, but unfortunately, it is mainly on the “bump” (up-wards) movement of the wheel, rather than on the “rebound” (down-wards) movement of the wheel… where it would be far more beneficial.’
Wheels falling off trailers – further information
Our published books are written much like this article. They are technically competent but in plain English. They include the Caravan & Motorhome Book, the Caravan & Motorhome Electrics and the Camper Trailer Book. Solar is covered in Solar That Really Works – for cabins and RVs. Solar Success is for homes and properties. For information about the author please Click on Bio.
References
Designing with Threaded Fasteners, Havil G.S, Mech. Eng., Vol 105, No 10, Oct 1983.
Medium/Heavy Truck Wheel Separations, National Transportation Safety Board, Report No. PB92-917004, NTSB/SIR-92/04, Sept 1992.
Myths That Must Be Shattered, Automotive Industries, (April, 1982) p.43.
Design Handbook, Loctite Corporation, (1968) 160 pages.
A Logical Approach to Secure Bolting, Havil, G.S. Soc. of Manufacturing Engineers Ref: AD80-329.
Fastening and Joining, Machine Design, Issue 1967, Vol 14, Penton Publishing.
The Use and Misuse of Six Billion Bolts a Year, Kerely J. J., NASA Goddard Space Centre. Delivered, 35th meeting of the Mechanical Failures Prevention Group, NBS.
Lithium battery rival
by Collyn Rivers
Lithium-ferro phosphate (LFP) batteries – a lithium battery rival
Lithium-ion and lithium-iron-phosphate (a lithium battery rival) are two types of rechargeable batteries. They share some similarities but differ in high-energy-density, long life-cycles, and safety. Lithium-ion is used in smartphones and laptop PCs. Lithium iron phosphate (LiFEPO4) is that used in RVs etc.
Lithium-iron phosphate is cost-effective and more stable at high temperatures. Lithium-ferro phosphate (LFP) batteries may prove a lithium battery rival. It increases the choice of chemicals for battery production. It also reduces reliance on the more expensive, and difficult to produce, lithium hydroxide.
If LFP sells as hoped, the lithium used will reduce. The lithium chemical of choice is then likely to change from lithium hydroxide to carbonate. It will also enhance flexibility in the chemicals for battery production. It will also reduce reliance on the more expensive, and difficult to produce, lithium hydroxide. The lithium used per kWh of storage capacity will reduce. Furthermore, the lithium chemical of choice will trend from lithium-hydroxide to carbonate. An even more compelling outcome is the use of lithium phosphate as a cathode powder precursor.
Lithium battery rival chemistries
Charge and discharge rates of a battery are governed by C-rates. The capacity of a battery is commonly rated at 1℃. This means that a fully charged battery rated at 1 amp-hour should provide one amp for one hour. The same battery discharging at 0.5℃ should provide 0.5 amp for two hours. At 2℃ it should provide two amps for 30 minutes.
Lithium-ion
Lithium-ion can consist of two different chemistries for the cathode: lithium-manganese oxide or lithium-cobalt dioxide. Both have a graphite anode. Lithium-ion has a specific energy of 150/200 watt-hours per kilogram and a nominal voltage of 3.6V. Its charge rate is from 0.7℃ up to 1.0 C. Higher charges can significantly damage the battery. Lithium-ion has a discharge rate of 1℃.
Lithium-iron phosphate (LiFePO4)
Lithium-iron phosphate has a cathode of iron phosphate and an anode of graphite. It has a specific energy of 90/120 watt-hours per kilogram and a nominal voltage of 3.2 -3.3 volts. The charge rate of lithium-iron-phosphate is 1℃. The discharge rate is from 1 to 25℃.
Lithium battery rival – energy level differences
There are significant differences in energy when comparing lithium battery rivals (lithium-ion and lithium-iron-phosphate). At 150/200 Wh/kg, lithium-ion has a higher energy density. This is handy for power-hungry tools etc., that drain a battery at a high rate. The available discharge rate for lithium-iron-phosphate, however, exceeds that of lithium-ion.
Lithium battery rival – life cycle differences
Lithium-iron-phosphate has a lifecycle of 1000-10,000 cycles. These batteries can handle high temperatures with minimal degradation. They have a long life for applications that need to run for a long time between charging.
For lithium-ion, the higher energy density makes it less stable. this is especially at high operating temperature environments. Heat also shortens its life cycle.
Long-term storage benefits
Both lithium-iron-phosphate and lithium-ion have good long-term storage benefits. Lithium-iron-phosphate can be stored longer as it has a 350-day shelf life. For lithium-ion, the shelf life is roughly around 300 days.
Safety advantages of lithium-iron-phosphate
Lithium-iron-phosphate has excellent thermal and chemical stability. Such batteries stay cooler in higher temperatures. It is also incombustible if mishandled during rapid charges and discharges or short circuit issues. Lithium-iron-phosphate does not normally experience thermal runaway. The phosphate cathode will not burn or explode during overcharging or overheating.
Another safety advantage of lithium-iron-phosphate involves the disposal of the battery after use or failure. A lithium-ion battery made with lithium-cobalt-dioxide chemistry is potentially hazardous. It can cause allergic reactions to the eyes and skin when exposed. Special disposal considerations must be made. Lithium-iron-phosphate is non-toxic. It can be disposed of more easily.
Applications for lithium-iron-phosphate and lithium-ion
Lithium-iron-phosphate is suitable for applications where safety and longevity are desired but do not need an extremely high energy density. Examples include solar energy storage and RVs. Such batteries are, however, slightly heavier as well as bulkier than lithium-ion.
Lithium offering a range of benefits
Advances in battery technologies have placed lithium as currently the best power source for portable high energy use devices. It’s long shelf life, and ability to provide a continuous source of power over long periods of time is why both lithium-ion and lithium-iron-phosphate are reliable alternatives.
Currently, lithium batteries cost more than nickel-metal hydride and nickel-cadmium batteries. The long life of lithium batteries, however, can equal out initial high costs. Key factors are:
- Highest energy density: lithium-ion
- Good energy density and lifecycle: lithium-iron-phosphate
- Stable chemical and thermal chemistry: lithium-iron-phosphate
- No thermal runaway and safe when fully charged: lithium-iron-phosphate
- Portability and lightweight characteristics: lithium-ion
- Long life: lithium-iron-phosphate and lithium-ion
- Low costs: lithium-iron-phosphate
The operating environment needs also to be a consideration as well as any vibration issues. For RVs, for example, the chemical stability of lithium-iron-phosphate (i.e.LiFePo4) is superior to that of lithium-ion.
Lead acid batteries for travel trailers – they are still a good buy
by Collyn Rivers
Lead Acid Batteries for Travel trailers
A 100 amp-hour 12-volt lead acid (or AGM) weighs about 33 lbs (about 15 kg). If the travel trailer can cope with that weight, (and a microwave oven is not in frequent use – see below) lead-acid batteries for travel trailers are still a viable buy. They are made in different shapes, sizes and capabilities. All work in a basically similar way. Energy is stored within them as a result of electro-chemical reactions between lead plates and a water/acid mix (called electrolyte). They are charged by imposing a voltage across them that is greater than the voltage ‘within’ them at the time. The greater that voltage difference the quicker and deeper batteries charge. When the battery voltage reaches the charging voltage, charging ceases.
Bosch deep-cycle lead-acid battery. Pic: Bosch.
Deep cycle lead acid batteries for travel trailers
A lead-acid deep cycle battery is intended to supply current consistently over time, but not short term high current. Its life is shortened if discharged regularly at greater than 25% or so of its amp-hour capacity. Its name misleads as none can provide the full amp-hours claimed on the label more than a few times without serious damage.
If correctly charged (see Battery Charging and Battery Chargers), a deep cycle battery can be brought up to 100% charge. In practice, few are. Some in travel trailers never exceed 70%. Their makers advise not to discharge below 50%. In practice, many users ignore that advice. They routinely use the batteries until lights go dim and the beer warms (at about 80% discharge).
If treated as above, no deep cycle battery will withstand more than about 100 such cycles. If run down to about 30% remaining, they are good for 150-200 cycles. Doing as the makers advise provides 500-1000 cycles. Despite this, magazine journalists routinely state that a fridge (for example) that draws 5 amps will routinely run for 20 hours on a 100 amp hour battery. You’ll see pigs flying in formation before a 100 amp-hour lead acid battery can do that.
How low should I discharge?
Deep cycle batteries are best seen as ‘less-shallow-cycle’ batteries. Their vendors sell you amp hours. You can use a few slowly for a long time, or a lot more (and/or) quicker for a much shorter time, but that relationship is not linear. Using a lot quicker, so the battery is often deeply discharged, will cost more per amp hour. Usage is mainly a trade-off between convenience and your bank account. Unless keeping discharge to about 40% remaining, the cheaper so-called traction batteries (such as Trojan) last as long.
At too low voltage, some appliances may be damaged. Water pumps rely on water flow for cooling. They may even stall and burn out if the voltage drops too low. Fan-cooled motors are particularly affected. This is because the amount of air shifted is proportional to the cube of the fan’s rotational speed – and that is related to voltage. Most fridges have a voltage sensing cut-out that disconnects the incoming power below 11.4 or so volts. This is usually claimed to protect the battery (which it does), but its main job is to protect that fridge motor from overheating. Apart from the above, running the battery way down is unlikely to harm other electrical equipment.
Battery capacity
The ideal approach (which may require solar) is to size batteries such that they routinely charge to plus 98% and discharge only by a probable 15-20%. This way the batteries remain 85%-90% charged most of the time. Used like that they may last ten years or more.
Microwave ovens – a battery trap
A microwave oven’s rating (in watts) is a measure of the heat it produces – not the energy drawn in doing so. A typical 800-watt microwave oven draws about 1200 watts. This is about 120 amps from a 12-volt inverter. Doing this consistently will damage deep cycle batteries of less than 350-400 amp-hours. Travel trailers and motorhomes commonly have microwave ovens, yet may have a battery of only 150 amp-hours.
| Percentage of charge: | 100% | 90% | 80% | 70% | 60% | 50% | 40% | 30% | 20% | 10% | 0% |
| Volts: | 12.75 | 12.65 | 12.55 | 12.45 | 12.35 | 12.25 | 12.10 | 11.95 | 11.85 | 11.75 | 11.65 |
Approximate voltages of deep-cycle batteries (rested for at least 12 hours). rvbooks.com.au
Starter Batteries
Engine starting requires 300- 600 amps, typically for two-three seconds. It only seems high. It discharges the starter battery by only 2%-3%. That charge is replaced within a minute or two of the engine starting. In practice, starter batteries spend most of their life at 65%-70% of full charge. Starter motors are designed accordingly.
To provide such heavy current, starter batteries have a large number of thin plates that present a large surface area to the electrolyte. This provides heavy current for a few seconds, but such batteries withstand only a few extended discharges. Flatten most ten times and they are dead.
AGM and gel cell batteries
Absorbed Glass Mat and gel cell batteries are heavier, bulkier and costlier than conventional lead-acid batteries. They charge more readily and may be discharged deeper with less self-damage. They can provide about 70% of their nominal capacity. This compensates in part for their greater weight, bulk and cost.
Charging lead-acid batteries for travel trailers
Older vehicle charging systems deliberately cut back charging at 70% of full charge. Many post-2000 and almost all post-2014 have alternators that produce far too low a voltage for effective charging. For all, the dc-dc alternator charging technique is so effective it is now the only way to consider doing it.
For charging from 230 volts, use only a high-quality multi-stage charger. These are not cheap, but a 10-15 amp such unit will outperform any chain-store 30-amp charger in its ability to charge deeply, quickly and safely. If this is done the batteries will last many times longer.
Maintenance of lead acid batteries for travel trailers
This particularly concerns those wet’ batteries (now used mainly only in big solar systems etc) but for all, keep the terminals clean. A tablespoon of bicarbonate of soda in a bucket of water acts like a charm. Once a year disconnect the terminals and clean them until shiny on their contacting surfaces. After reconnecting, coat with Vaseline or battery protection fluid.
If relevant, check water levels at least every eight to ten weeks. A correctly charging wet battery should use some water. About 10-20 mm every ten weeks is normal in temperate climates. If less, the batteries are probably being undercharged. If much more, and unless you are in a very hot area, they are possibly being overcharged.
Avoid Christmas trees of cables hung off battery terminals. Instead, install one or more common power posts, and take a single heavy cable from there to the battery terminal.
Future of lead-acid batteries for travel trailers
Conventional lead-acid batteries were developed over 150 years ago. They have only barely advanced in their energy holding capacity (that is closely related to the weight of their lead plates). Despite this, they are still a good buy for travel trailers and motorhomes. They are likely to be used for some time to come, also in large solar systems etc.
Gel cell batteries for travel trailers still have a following, but AGM batteries are now more commonly used. Both are increasingly challenged by lithium-ion battery technology. There are now also other contenders.
Further information
There’s a huge amount more about batteries for travel trailers in my books Caravan & Motorhome Electrics, Solar that Really Works (for travel trailers and motorhomes) and Solar Success (for home and property systems). My other books are the Caravan & Motorhome Book, and the Camper Trailer Book.
See also article Battery Charging and Battery Chargers. For an in-depth academic (but readable view) see How Long Can Lead Acid Batteries Last.
This article is copyright RV Books, 2 Scotts Rd, Mitchells Island, NSW 2430.
Solar usage in the USA
Solar usage in the USA
Solar usage in the USA is rapidly becoming cheaper and growing increasingly faster.
In 2004, the average price of an installed 10 kilowatt rooftop solar module was about US$3.50 per watt. As of early 2021 an installed 10 kilowatt system is likely to ranges from $17,750 to $24,000 ($1.77 -$2.40 per watt).
Amount of solar energy available in the USA in a calendar year. Pic: https://www.nrel.gov/
How does system size impact the cost of solar?
Knowing the average cost per watt is helpful, but what does $1.77-$2.40 per watt actually mean for you? The cost of installing solar depends primarily on how much electricity you want to generate – a bigger system will cost more because you’ll need to buy more equipment and more labour will be needed to install it.
Solar usage in the USA – higher solar cell efficiency
This fall in price is due mainly to higher solar cell efficiency. Until recently, most high-quality solar cells were about 18% efficient. In 2020, however, the global JinkoSolar company raised that to 24.79%. The launch of those ultra-efficient modules lowered the USA’s domestic average cost of solar-produced electricity. It is now (early 2021) about US$38 per megawatt-hour (MWh). This cost is similar to that of producing electricity from newly built coal-fired power plants. Currently, the most efficient solar projects in Chile, the Middle-East and China produce electricity for under US$30/MWh. Wind power projects in Brazil, the USA and India are likewise.
The rise in production capacity and efficiency is primarily in China. It is now the centre of global solar panel manufacturing. China’s module production was 17% higher in early 2020 than in the same period of 2019. This despite exports falling slightly.
The implications of solar energy increase are immense. Overall emissions are substantially reduced. Apart from making, transporting and installing solar modules and associated electronics, it is zero thereon. Most solar modules last for at least 25 years. Meanwhile, appliance makers seek to reduce energy use.
Renewable energy tax credits
Under the Consolidated Appropriations Act of 2021, the renewable energy tax credits for fuel cells, small wind turbines, and geothermal heat pumps now feature a gradual step down in the credit value, the same as those for solar energy systems.Tax Credit:
- 30% for systems placed in service by 12/31/2019
- 26% for systems placed in service after 12/31/2019 and before 01/01/2023
- 22% for systems placed in service after 12/31/2022 and before 01/01/2024
Expires: December 31, 2023
Details: Existing homes and new construction qualify. Both principal residences and second homes qualify. Rentals do not qualify.
The USA’s solar energy market is forecast to increase. That increase is a likely (compounded) annual 17.3% throughout 2020-2025. Tax credits on renewable energy-related matters may expire in 2021. Solar power investors in solar power will expedite finishing projects. This trend may partly offset COVID-19 investment impacts.
A 30% tariff on solar module imports has already forced USA producers to become more competitive. Furthermore, to increase domestic manufacturing. Cost-effective battery energy storage technology is also needed. Significant developments are already well underway.
It is now all but sure that solar (and wind) power will continue to displace traditional base-load power sources. This will happen not just in the USA. It will be worldwide.
Generator Battery Charging – Quickly and Deeply
Generator Battery Charging – Quickly and Deeply
Quick and deep generator battery charging is totally possible. You must, however, know how to do it. This article reveals all. It explains why and how. The article is valid for both 120-volt and 240-volt generators.
All such generators have a 12-volt DC socket. Some generator makers label it ‘Battery Charger’. This socket, however, is intended to power small 12-volt devices, such as a TV directly. Its output is a typically unregulated 13.6-volts. It drops under load (to 12.6-volts or less). That voltage is, nevertheless, fine for running 12-volt lights and appliances.
Lead acid and AGM batteries
A generator’s typically unregulated 13.6-volts is far too low for full and speedy battery charging. It may half-charge a flat 100 amp-hour lead-acid or AGM battery within six or so hours. From there on, charging progressively reduces. It may take further 24 hours to charge it over 70%. And a week or more more to fully charge it.
The solution is simple and effective. Charge the battery via a 240-volt (or 120-volt) battery charger powered by the generator’s 240-volt (or 120-volt) outlet. The size charger required (and its safe charging rates) varies with battery capacity and types. This is particularly so for LiFePO4 batteries.
As a general guide, most lead type batteries below 180-200 amp-hour typically have a recommended maximum charging current of less than 40 amps. For these a 25-amp charger is adequate.
Charging Voltage
Recommended maximum charging voltages for most AGM or gel batteries are around 14.6 volts,but always check the manufacturer’s recommendation.
For lead-acid and AGM batteries once fully charged, to avoid overcharging and to extend battery life, the charger should drop to about 13.2-13.3 volts.
Charging in high temperatures
Battery maker charging recommendations usually for an ambient temperature of 250 C. Regardless of battery type, if charged in a high-ambient temperature environment, such as an engine bay, check the battery manufacturer’s related recommendations. Some batteries (particularly AGMs) are not suitable for engine bay installation. Some battery warranties are void if installed in engine bay temperatures. read more…
Should I grease my tow ball?
Should I grease my tow ball?
Tow ball friction plays a vital role in reducing travel trailer sway
Should I grease my tow ball is a question asked by travel trailer owners worldwide. A recent poll in Australia showed that slightly over half do so, but primarily to reduce wear.
Tow ball friction plays a vital role in reducing travel trailer sway. Those owners who grease them unwittingly prejudice safety for the possible need to renew the tow ball every ten or so years. In practice a non-greased tow ball has negligible wear. Even it were to need replacing, the cost to do so is a mere A$15-25.
The common advice to use grease for trailer hitch ball is misplaced. RV Books advises that you do NOT grease that tow ball – nor use any liquid or powder that may reduce that vitally needed friction. While tow ball friction is only one factor it’s one of a range of issues that factor into how to stop travel trailer sway.
Adding tow ball friction
The world-wide AL-KO company produce a tow ball that has four friction linings forced against the tow ball from both sides plus the front and rear. In technical terms, they exert the equivalent clamping torque of 320 Newton/metres force. In Australian terms, this is ‘b-y tight!’. Swaying or pitching movements are effectively suppressed before they become serious.
The AL-KO friction tow ball hitch.
Friction anti-sway limitations
Any hitch (or add-on friction sway control) has a fundamental limitation. This is that unless deliberately increased, frictional force remains constant. The vectored sway forces that they dampen, however, increase with the square of the road speed. Any form of friction hitch or friction stabiliser is thus only marginally effective at (say) 100 km/h (about 62 mph). This was actually confirmed (following extensive controlled testing) in a technical paper some years ago.
That any given frictional force remains a constant is why most UK/EU travel trailers use the friction hitch (for low/medium speed) comfort. They rely on electronic stability systems (that brake the trailer’s wheels) at high speed. Even here, the makers are cautious. They advise that while usually effective, these systems cannot overcome the more basic laws of physics. Ignore all advice to lubricate, or any friction-reducing manner a trailer tow hitch.
How travel trailer and tow vehicles interact
by Collyn Rivers
How travel trailer and tow vehicles interact
How travel trailer and tow vehicles interact is basically this. A trailer towed via an overhung hitch is fundamentally unstable. Minimising the causes ensures stability within limits.
By the mid-1920s vehicle-drawn travel trailers were common. From their beginning, they had handling problems. Now, (2020) reports of rigs jack-knifing and overturning still increase. Most now relate to long end-heavy twin-axle trailers towed by lighter vehicles.
Identifying the cause
In the early 1900s, central axled, heavy transport trailers towed via overhung hitches, were unstable. This worsened as towing speeds increased. Fruehauf (USA) realised hitch overhang imposed lateral forces on tow vehicles. As trailers yawed clockwise, that overhang caused tow vehicles to yaw anti-clockwise. And vice versa. The longer that hitch overhang, the greater the effect.
Figure 1. This shows the inherent problem with a conventional travel trailer. If one part of the rig yaws it causes the other to yaw in the opposite manner. Pic: copyright RV Books, Mitchell Island, NSW, Australia. rvbooks.com.au
Locating the hitch over the tow vehicle’s rear axle/s eliminated side forces (Figure 2) solved the problem. It led to the semi-trailer concept. The transport industry adopted it world-wide. It has used it ever since.
Figure 2. The fifth wheel concept. Yawing of one or other part of the rig barely affects the other. Pic: rvbooks.com.au
Early vehicles used for towing rarely exceeded 30-40 mph (approx. 50-65 km/h). Nevertheless, their overhung hitches caused rollovers. Curiously, early travel trailer makers and owners seemed unaware of this – let alone the known cause. Many still are!
Travel trailer and tow vehicle dynamics – early understanding
Travel trailer and tow-vehicle dynamics began to be understood in the 1970s. Studies, plus practical testing, revealed the causes of instability. These included trailer yaw inertia, inadequate nose weight, poor weight distribution and incorrect axle positioning. Tow vehicle tire pressure and side-wall stiffness affect stability. Furthermore, that all such causes interact.
It was initially believed that excess trailer weight relative to the towing vehicle was a major concern. It is only recently realised that excess trailer length is an even greater issue. Furthermore, poor loading and excess speed are always involved.
Travel trailer and tow-vehicle dynamics – terms used
Mass and weight: these are different concepts.
Mass: is the amount of matter within a body.
Weight: is a measure of the force caused by the downward pull of the Earth’s mass (gravity) on mass. It is that which keeps your feet (and an RVs tires) on the ground. For, the purposes of the article, unless stated otherwise, mass and weight can be seen as identical.
Laws of Motion: In 1668, Newton defined the laws of motion. They usefully describe travel trailer and tow vehicle behaviour.
Law 1. Unless influenced by an external force, mass remains at rest. If a force causes a mass to move it continues to do so at a constant speed. Unless deflected by an external side force it moves in a straight line.
An otherwise stable vehicle towing an equally stable travel trailer will normally stay in a straight line. A side wind gust, however, may deflect it.
Law 2. The rate of change of a masses’ momentum is proportional to any applied force. It acts in the direction the force is acting. For example, a powerful vehicle can accelerate a rig quicker than a less powerful vehicle.
Law 3. To every action, there is an equal and opposite reaction. Jump backwards off a skateboard, and that board is propelled strongly in the opposite direction.
Force: is any influence that causes a mass to accelerate. The greater the force applied, the greater the rate of change of acceleration. That rate of change is directly proportional to the force acting upon it. It is inversely proportional to the mass of that body. Force has both magnitude and direction. Describing it requires both terms.
Moment arm: A moment arm is a lever. A simple example is a wheelbarrow’s handles. Others include tow-hitch overhang and weight along a travel trailer‘s length.
Torque: is the effect of a force causing something to roll or rotate. It enables revolving wheels to cause a car to move. Or the action of using a spanner to tighten nuts.
The terms ‘torque’ and ‘moment arm’ means much the same. The term ‘torque’ is used where there’s some form of powered turning. An example is closing a heavy door. Pushing near its hinge requires more force but less movement. Pushing further from the hinge requires less force but more movement. The work that is done and energy exerted, however, is the same.
‘Moment arm’ relates to levers. An example is an adult and a child on a see-saw. Balance is only possible by the adult sitting closer to the pivot. Or the child sitting further away. A similar effect is a weight on a travel trailer‘s rear. Its effective is far greater than if close to its axle/s.
Inertia: Inertia is virtually any resistance to change. It’s a tow vehicle’s ability to keep moving at the same speed and in a straight line unless steered otherwise. Or, if jack-knifing – to be straightened.
Momentum: is a measure of the quantity of motion. A moving trailer and its tow vehicle’s momentum is its combined weight times its speed.
Acceleration: relates to change in a mass’s rate of movement. It may be positive (e.g. increasing speed). Or negative (e.g. when braking). It is measured by dividing velocity (metres per second) by seconds. In Imperial units, it is 32.2 ft/s. The unit is often shown as ‘G’ (correctly it is ‘g’). A driver cornering at advised road sign speed experiences about 2 g.
Moment of inertia: is a measure of an object’s resistance to changes in rotation. In imperial (US) units it is shown in pound-foot-second squared (lbf.ft.s2). In metric units, it is shown in kg/m².
A trailer’s such resistance to rotational change can be calculated. It is done by theoretically ‘cutting the trailer into thin slices’. Each slice has a mathematically describable shape.
The moment of inertia can also be measured. It can be done by locating the trailer on a friction-free turntable. That turntable is then rotated by about 30 degrees against the force of springs. It is then suddenly released. The time taken for the trailer to re-centre is a measure of its moment of inertia.
Radius of Gyration: this where a trailer’s centre of mass would be, were all its weight in one place. That centre of mass should ideally be just ahead of its axle/s. A travel trailer must never be rear-end heavy.
Work has a specific meaning. It refers to transferring energy or applying force over a distance. One example is lifting a heavy object.
Energy is the ability to perform work. It can be expressed as force times displacement in a given time. An example is stacking goods on a high shelf.
Potential Energy is the capacity of something to do work by virtue of its position or configuration. A compressed spring contains potential energy. So does the water in an elevated tank.
Kinetic Energy is associated with motion. Moving objects perform work as a result of moving. Kinetic energy is proportional to the square of a mass’s velocity. A tow vehicle and trailer at 60 mph (just under 100 km/h) have four times the kinetic energy than at 30 mph (just under 50 km/h). This is why it is dangerous to tow at excess speed. Never tow above 60 mph.
Power: is the amount of work done in a unit of time. When you tow your trailer up a hill the work done is always the same. Doing so at 60 mph, however, needs more power, but for a shorter time, than at 30 mph.
Yaw: is a rotational or rocking movement. An example is a trailer rocking around its axle/s. Many travel trailer owners refer to this as ‘sway’. This confuses. When a trailer sways (rolls) its centre of gravity moves sideways.
Yaw Force: is the effect of (say) a side wind gust that causes a trailer’s front or rear to be pushed sideways. The greater that force, the greater the rate of change of that movement.
Yaw Inertia: can be seen as the resistance of a travel trailer to yaw when subject to a side force (‘yaw’). It can also be seen as the reluctance to cease yawing once started. (It’s like staying in bed on a cold morning).
Tire behaviour
Horse-drawn carriages had pivoted front axles. This ensures their wheels aligned with the pulling force. But if cornered too fast, the carriage’s inertia overwhelmed the horse’s grip. They would lose control. The carriage’s momentum, however, would cause it to keep moving. Then often overturn.
Tires back then had to revolve, but not sink nor fail under load. Their marginal grip only partly resisted sliding. Braking was by ordering the horses to slow down. Also levering against a tyre to prevent it rolling. The main forces: for traction, steering and slowing, were external, via animal power.
A powered vehicle has similar limitations, but with a major difference. Forces for moving, braking and steering are applied and reacted only by its tires.
A travel trailer’s tow vehicle acts physically much as those horses. The trailer depends on the stability of whatever pulls it – as did horse-drawn carriages. This is often overlooked. Pic: courtesy of fineartamerica.com.
Early pneumatic tires
The pneumatic tires used on early cars were like oversized-bicycle tires (and solid tires). They rolled more or less where pointed. When forces exceeded their grip, such tires slid progressively and predictably.
Then cars became heavier and faster. Tires became balloon-like. Owners, particularly in the USA, sought a softer ride. Doing so, however, caused cars to handle poorly. And often unpredictably.
By the mid-1930s it was understood how suspension and tire interaction dictates handling. This particularly applies to travel trailers and tow vehicles. Their ultimate behaviour is dictated by their suspension and tires. Not all travel trailer makers and even fewer travel trailer owners know this. Let alone why and how.
Tire basics
An inflated tire does not roll over a surface. It has a caterpillar-like action. It lays down and picks up an elongated oval of tread (called its footprint). That footprint’s stability is determined by tire construction and air pressure.
Steering a tire is like twisting a rolling balloon. Torque is applied, via the wheels’ rims, to the tires’ sidewalls. The sidewalls flex, and via their stiffness and air pressure, cause the footprint to distort as directionally required. That footprint’s grip is partly molecular and partly frictional.
The steered tires’ footprint’s distortion creates an angular difference between where wheels point and the vehicle travels. That angular difference is called ‘slip angle’. The greater the tire width, sidewall and tread stability and tyre pressure, the lesser the slip angle.
The term slip angle, however, can mislead. In normal driving, the footprint does not slip. That footprint is caused (by torque applied to the tire’s sidewalls), to stretch and distort. It is only when side forces totally overcome footprint grip that tires actually slide out of control.
A typical tow vehicle tire (green) increases ‘cornering power’ as its slip angle increases. It then levels off and starts falling away sharply. The latter introduces major and possibly terminal oversteer. It can result in jack-knifing.
A tire’s footprint grip is not linear with imposed weight. When cornering, weight, (or any weightless downforce such as that from the so-called ‘wind spoiler’ used at the rear of racing cars) imposed on tires increases their cornering power. It does so, however, by only 0.8 or so of that increase in grip.
Interaction of tire slip angles
Interacting front/rear tire slip angles dictate vehicle handling. Passenger vehicle front tires have slip angles that normally exceed their rear tire slip angles. This effect, called understeer, causes vehicles to veer away from side-disturbing forces. (So, likewise, do correctly-trimmed yachts and aircraft).
If cornered too fast, an understeering vehicle automatically increases its turning radius. This reduces side forces, and hence slip angles. If, however, rear slip angles exceed front slip angles, the vehicle adopts an ever-tightening spiral. This causes its rear slip angles constantly to increase. Unless the driver applies opposite steering lock, the rear tire slip angles increase until their footprints lose control. The vehicle then jack-knifes or spins.
Understeer and oversteer. In mild form, understeer adds stability. If the vehicle is corned too fast, it automatically adopts a wider radius turn, thus reducing undesired forces. Too much understeer, however, can result in the (upper) example above.Oversteer (in all except rally cars) is undesirable. Once oversteer sets in, unless instantly corrected – by applying opposite steering lock – it rapidly escalates and usually results in the vehicle spinning out of control. Pic: www.driversdomainuk.com/img/oversteer.jpg (original source unknown).
Rear tire distortion can cause oversteer. Such distortion can result from a yawing travel trailer. It imposes side forces on the tow vehicle’s rear. Other oversteer causes are excess tow ball weight or too low tow vehicle rear tyre pressures.
Neutral steer may seem desirable. It is not. Neutral steer requires constant steering correction to overcome road camber. It causes a vehicle to be demanding and tiring to drive. Neutral steering is also impossible to maintain. Even minor changes in tire pressure, loading, or road camber will then cause understeer or oversteer.
Maintaining footprint balance
A rig’s dynamic behaviour depends ultimately on tow vehicle tire behaviour. This necessitates its tires firmly gripping the road. Despite this, some trailer makers maintain that their products do not need shock absorbers. They argue that inter-leaf friction provides adequate damping. Such damping, however, only acts as the spring’s compresses. On the rebound, however, the spring leaves are no longer held in firm sliding contact. As a result, release their rebound energy instantly. That energy jack-hammers the wheel back down. As the wheel impacts the ground it imposes shearing forces on wheel studs and stub axles. This causes those studs to snap. Stub axles break. Wheel bearings needing ongoing replacing. See Wheels Falling off Trailers.
Inadequate or non-existent spring damping also prejudices electronic stability systems. These rely totally on trailer braking. Brakes, however, are only effective when tires are firmly on the ground. Without adequate spring damping, they are not.
Slip angles and load/tire pressure etc
A tire’s cornering power decreases with load and increases with tyre pressure. Adding tow ball mass necessitates increasing (tow vehicle) rear tire pressures to retain the required slip angles. Those rear tires need to be 7-10 psi ( 50-70 kPa) higher when towing. Never increase tow vehicle front tire pressure beyond that in normal driving.
If a vehicle’s front/rear weight balance is unchanged, its tires front and rear slip angles increase proportionally while cornering. The vehicle’s balance is maintained. But if its rear tires loading only increases (as when a trailer yaws), front/rear slip angles change accordingly. If that induces oversteer, the rear tire footprint may lose all grip. If that happens the rig is instantly triggered into a jack-knifing sequence.
Adverse effects of tow vehicle suspension changes
The relative tire loading front/rear (and hence slip angles) is not just a function of weight distribution. It depends on how the suspension resists roll.
Never stiffen rear suspension without stiffening the front proportionally. Stiffening the rear alone causes more of the vehicle’s resistance to roll to be borne by its outer rear tire whilst cornering. That increases its slip angle. If that footprint collapses or slides, jack-knifing is likely. This is not just theory. It happens.
Minor spring rate changes are rarely detectable in normal driving. This is why many claim it’s safe. But by stiffening rear springing alone a strong yaw force can trigger that vehicle into sudden and terminal oversteer.
If a vehicle’s suspension needs upgrading it’s being overloaded. Suspension changes require serious expertise. Not adding airbags sourced from eBay.
Tow ball weight
To keep a travel trailer straight, front end weight is essential. That in Australia has long since been taken as 10% of gross trailer weight. Now (2020) many have as little as 4%. The British, whose travel trailers are 40% lighter (per metre) opt for 6-7%. Americans may use as high as 14%.
Basing a trailer’s tow ball weight on a percentage of travel trailer weight has long been routine. What matters far more, however, is a travel trailer’s length. Furthermore, where mass is distributed along that length. Because of this, even 10% may be too low for a long end-heavy travel trailer. This is an ever-increasing problem. Vehicle makers continue to reduce tow ball weight limits. And tow vehicle weight decreases.
To keep sway from building-up, Australian and US-made travel trailers typically need 550-770 lbs (250-350 kg (550-775 lb). nose weight. Such weight, however, thrusts the tow vehicle’s rear end downward. As with pushing down on the handles of a wheel-barrow, that nose weight causes the vehicle’s front to lift. This undesirably shifts weight from the tow vehicle’s front (steering) tires.
The Hensley hitch
In 1971, the USA’s N. Gallatin obtained a patent (US 3790191 A) for a trapezoidal trailer hitch. This hitch comprised first and second, spaced apart hitch members pivotally connected at their rearward ends to the forward end of the trailer and pivotally connected at their forward ends to the rearward end of a truck or the like. https://patents.google.com/patent/US3790191A/en. Shortly after (in 1971), the US Hensley company patented a not-dissimilar version, but not integral to the tow vehicle.
That effect of both patents was to geometrically extend the virtual tow ball further toward the tow vehicle’s rear axle. The Hensley unit became widely used. The hitch weighs about 42 pounds (approx. 20 kg [44 lb]). Most US travel trailers over about 20 feet (about 6 metres) use one.
Weight distributing hitches – and drawbacks
Developed initially in Australia (in 1950), but adopted almost immediately in the USA, a weight distributing hitch (WDH) forms a semi-flexible springy beam between tow vehicle and trailer. This reduces the weight otherwise imposed on the tow vehicle’s rear tires. It also restores some of the otherwise reduced weight on its front tires.
A WDH, however, can only counteract downforces on the tow vehicle’s rear tires. Although the downforces on those rear tires are reduced by the WDH, those tires are still carrying much of the tow ball mass. They must still resist travel trailer yaw forces, but a WDH cannot reduce those yaw forces.
That not realised by almost all travel trailer owners, and even some makers, is that a WDH inherently reduces a rig’s ultimate cornering ability. It does so typically by about 25%. This issue is recognised and addressed by the US Society of Automobile Engineers in its current SAE J2807 recommendations. These recommendations are now followed by all US (and the top three) Japanese vehicle makers.
That (SAE J2807) recommendation includes advising to adjusting a WDH to correct no more than 50% of the tow vehicle’s rear end droop. Never the full amount. It suggests correcting 25% of that rear end droop is better. Such advice has long been given by Cequent in the USA. (Cequent owns Hayman Reese). Hayman Reese locally used historically to advise levelling the rig. It now follows the Cequent (USA) advice.
A WDH is only required when the download on the tow vehicle’s rear tires is not acceptable. If it is acceptable you can readily compensate for that weight shift. To do so, increase tow vehicle rear tire pressures by 7-10 psi (50-70 kPa).
Trailer independent suspension can have downsides
Passenger car independent (front) suspension stems from the USA in the 1930s. It resulted from a buyer demand for softer suspension. Softening and increasing spring travel, however, resulted in beam front axle wheel ‘tramping’. The wheels would alternately jump up and down and swing violently from lock to lock. This particularly happened with poorly damped and/or soft suspension long-travel suspension.
Around 1934, General Motor’s Maurice Olley established this was a ‘gyroscopic precession’. You can experience this by holding a bicycle’s front wheel off the ground, spinning it and then swinging it in an arc. It imposes an unexpected swaying effect. This can also be shown via a gyroscope.
![How [cara] and tow vehicles interact - electric vehicle batteries,book on batteries,electric car batteries,lithium ion batteries for electric cars,electric car battery technology,how long do electric car batteries last,electric vehicle battery life](https://solbsau.centrails.com/wp-content/uploads/2014/12/gyroscopic-precession-e1624597949506.jpg "How [cara] and tow vehicles interact 93")
Here, (US) teacher Gary Rustwick demonstrates the effects of gyroscopic precession. He swings the spinning wheel in an arc whilst standing on a free-moving turntable. As he does so precession forces cause the turntable to rotate.
Wheel precession is dangerous. If it builds up, the vehicle becomes unsteerable. Worse, reducing speed (as one must) decreases the tramping frequency but increases its amplitude.
Need for steered wheel stability
In the early 1930s, General Motors’ Maurice Olley realised precession was only totally preventable by ensuring steerable wheels rose and fell vertically. Not forced to move in an arc created by a tilting beam axle. Achieving this required steered wheels to be suspended independently.
This concept was not new. It was used on a road-going steam locomotive in the late 1800s. Lanchester used it in 1901, Morgan in 1911, Lancia and Dubonnet in the 1920s. But all did so to reduce unsprung mass and improve the ride. Olley knew that too, but also that independent (and vertical) front wheel travel was necessary for soft suspension.
Non-steerable wheels are subject to the same precession forces. As they cannot swivel, however, such forces do not matter. This is why many cars and almost all trucks and many 4WDs retain beam-axle rear suspension.
Travel trailer wheels do not steer
As travel trailer‘s wheels do not steer there is no inherent need or benefit for independent suspension. Nor is there any need for suspension travel greater than that of their tow vehicles. For much of the time, a travel trailer rocks on an axis around its tow hitch. Many, for seemingly marketing reasons, have ultra-soft suspension like some American cars of the mid-1930s. Almost all currently-made cars are much firmer. They also have less suspension travel. And do not wallow.
The US-made Airstream is an exception. Right from its beginning in the early 1930s, its pre-tensioned rubber suspension provides a firm but adequately-soft ride. The suspension is independent.
Suspension issues
Human physiology dictates passenger vehicle suspension. The result is compromised by the brain’s response. Nausea is created if the suspension is too soft, and physical discomfort if too hard. Such constraints do not apply to non-human carrying trailers. It is thus absurd for their makers (particularly in Australia) to base the suspension on huge US cars (such as Chevrolets) of the mid-1930s. For optimum road holding, travel trailer suspension needs to be firm. This can readily be done and with no risk to any contents.
Fifth-wheel trailers more stable
A fifth-wheel travel trailer pivots from a hitch above the tow vehicle’s rear axle/s. Side-wind gusts may cause the trailer to swing slightly, but the forces are low and quickly self-damp. They do not affect the tow vehicle. Drivers are rarely aware of them. As long as a fifth wheeler’s rear wheels are well back, the weight on the tow vehicle is within that vehicles’ limits. A well-balanced fifth wheeler is stable at any speed.
Action and reaction
As described earlier in this article a hitch distanced behind a tow vehicle’s causes a trailer to yaw if that tow vehicle yaws – and vice versa. This would not overly matter if the trailer yawed in the same direction. That overhung hitch, however, causes the opposite. If the tow vehicle yaws clockwise, its overhung tow ball yaws anticlockwise. As it does, it takes the nose of the trailer with it.
Likewise, if the travel trailer yaws clockwise, that overhung tow ball swings the rear of the tow vehicle anticlockwise. This is the root cause of conventional trailer instability. The longer that overhang, the greater the (undesirable) effect.
At low levels, yaw interaction is mainly annoying. It is reducible (at low speed) by friction and other forms of damping. It typically dies out after two or three cycles. If it does not, it indicates instability. That needs resolving at its source. Friction damping is almost useless at speed. This is because the friction stays constant. Yaw forces, however, increase with the square of the rig’s speed.
Severe yaw is serious
If severe yawing occurs above a critical speed (specific to each rig and its loading) the yaw may self-trigger into jack-knifing. It is fuelled by the rig’s kinetic energy. Once triggered, if travelling at speed, this sequence is almost impossible for a driver to correct.
Musicians and public speakers experience a similar effect. If their microphone picks up the sound from the loudspeakers, that sound suddenly develops a full-on yowl. This is only stopped by drastically reducing the volume (akin to braking a travel trailer). Or by moving back from the loudspeakers (akin to reducing tow hitch overhang).
Critical speed
Depending also on loading, every combination of a tow vehicle and travel trailer has a so-called critical speed. Once above that speed, yawing can irreversibly escalate out of the driver’s control.
That critical speed, and the degree of yaw, is directly associated with the tow vehicle’s mass relative to the trailer’s mass (and particularly mass distribution). It is also associated with trailer length, hitch overhang, tyre type and size, sidewall stiffness and pressure etc.
All of the above (and more) is involved. The longer and the lighter the tow vehicle (and its tow ball mass) the lower that critical speed. The onset of critical behaviour is sudden. Because of this, the still-common suggestion ‘accelerate to dampen yawing’ is risky except at very low speed.
The critical speed effect does not imply that the rig jack-knifes if that speed is exceeded. If, however, a rig is travelling at or above its critical speed, a strong side wind gust, or a strong swerve makes jack-knifing more likely. Few owners encounter this, so many dismiss its possibility.
Avoiding jack-knifing
When a travel trailer yaws, it transfers the yaw force via the overhung hitch to the tow vehicle. The transmitted forces are resisted by the tow vehicle’s weight and the grip of its tires. Minor trailer braking assists straightening the rig. Heavy trailer braking, however, may overwhelm the trailer’s tires as they are already stressed by yaw forces.
If a travel trailer yaws never apply tow vehicle braking. Doing so may trigger that tow vehicle’s already stressed rear tires into terminal oversteer – such that it spins.
Beware of cruise control
Cruise control detects the minor drop in speed when yawing occurs. It nevertheless attempts to restore the set speed and the tires slip angles increase. While convenient, it is thus better not to use cruise control when towing a heavy trailer at speed.
Wind effects
A further cause of major travel trailer instability is wind forces from fast-moving trucks. This is particularly so of trucks towing trailers; and even more so if the truck has a flat front (rather than a bonnet). That bluff front creates an ongoing strong bow wave plus a vortex (i.e. a rotating wind gust) along its side.
If overtaking (or being overtaken) a tow vehicle and travel trailer will experiences wind buffeting. As the trailer’s tow vehicle approaches the rear of the truck cab, a side wind vortex initially causes the tow vehicle to be drawn toward the truck. As the tow vehicle draws closer to the front of the truck cab it is hit by the truck’s strong side-going bow wave. This causes the trailer to swing slightly away from the truck. The overhung hitch causes the front of the trailer to sway toward the truck. A vortex pulls it in further. This initiates a rapidly developing yaw cycle. Jack-knifing can result.
A generally similar but less common effect occurs when a truck and a travel trailer rig are approaching each other at speed on narrow roads.
Electronic stability systems
Electronic stability systems monitor trailer yaw. AL-KO’s applies travel trailer braking when it detects ongoing yaw forces exceeding about 0.2 g. The maker warns the system is an emergency aid. It is intended to prevent accidents. It does not enhance stability.
The Dexter system applies the travel trailer’s brakes asymmetrically (i.e. out of phase with the yaw). It does so at lower yaw acceleration levels. As testing is done at 60 mph (just under 100 km/h) the ability (except as a yaw reducer) to prevent a catastrophic incident at speeds above the critical speed is unknown. Both Dexter and AL-KO (now one company) emphasise their products cannot override the laws of physics.
Enhancing rig stability
The major factors include everything that affects front/rear tyre slip angles. Those within owner control include:
Loading and load distribution of the trailer and tow vehicle.
Excess tow ball overhang caused by unnecessary hitch bar extension.
The speed at which the rig is driven.
Fitting and use of yaw control devices, WDHs etc.
Those outside direct owner control (but subject to the choice of rig) include:
Length of the trailer, the unladen weight of the trailer.
Weight and stability of the tow vehicle.
Those determined by the trailer builder include:
Length of the trailer.
Weight of the trailer.
Distance from trailer tow hitch to axle centre/s.
Distribution of weight along the length of the trailer (particularly at its rear).
Centre of mass (i.e.weight) in both planes.
Height of the roll centre and roll axis (as imposed by the geometry of the trailer’s suspension).
Moment Arms about the roll axis, particularly at the far rear.
The magnitude of yaw inertia.
The radius of gyration.
Damping of yaw and roll.
Tires with good sidewall stability (such as light truck tires).
Optimising towing stability (summary)
Tow vehicle behaviour is now well understood and proven. That required is a long-wheelbase vehicle with a short rear overhang that weighs at least as much as the trailer. Towing three or more tonne behind a 2.5-tonne dual-cab ute is an accident awaiting the circumstances to trigger it.
A major undesirable factor with travel trailers is excess length. Excess weight matters, but excess length is now known to be a far greater issue.
Reducing trailer perimeter weight, and particularly rear-end weight, is vital. If feasible house a trailer spare wheel below the chassis and in front of or just behind the axle. Batteries are best located centrally between the axles. Water tanks should be wide but not long and located as centrally as possible.
Friction devices smooth low speed snaking, but have a negligible effect at high speed. One that works well at low/medium speeds is likely to be less than 1% effective at 100 km/h (62 mph). Elastic energy held within sprung-cam devices may suddenly be released when such devices are overwhelmed – and ‘fed into the system’.
Lateral sidewall stiffness of all tires assists.
The major factor, however, is excess speed.
Driver reaction
Most big rigs feel stable in normal driving. There is also usually sufficient stability to enable an experienced driver to cope with scary but not accident-resulting situations.
A major issue is that (particularly) with heavy rigs, unless grossly unbalanced, it is not possible for a driver to know (by feel or ‘experience’) how that rig will behave in an emergency. Most big rigs feel ultra-stable. Short vans are more stable but may feel twitchy (particularly if twin axle). The concern is how the rig behaves in situations that cause major yaw. These include sudden strong side wind gusts on a motorway, braking hard on a steep winding hill at speed, and swerving at speed.
‘My rig always seemed so stable’
Police say the most after-accident reaction is: ‘my rig always seemed so stable until it suddenly jack-knifed’. Such apparent stability is typical of container ships and car ferries, until a rogue wave or turning too sharply proves otherwise.
There is increasing evidence that the safe maximum speed for big rigs is under 60 mph (about 100 km/h). This is related to tow ball weight. Furthermore, the lower that weight, the lower the safe speed.
Trailer and tow vehicle dynamics – Summary
The above is a precis of some of the most relevant parts of RV Books Why Caravans Roll Over – and how to prevent it. The book is written in plain English but has a fully referenced final technical section.
Acknowledgement
My articles in this area primarily summarize current thinking. They stem from my interest and involvement while employed by Vauxhall/Bedford’s Research Dept in the 1950s, and particularly by the influence of Maurice Olley.
Maurice Olley was born in Yorkshire in the late-1800s. Following time as Rolls-Royce’s Chief Engineer, he worked with General Motors Research Division. He later returned to Vauxhall Motors (UK). I was privileged to attend his lectures during my years at Vauxhall Motors Chaul End Research Centre
Upgrading solar system has unexpected traps
Upgrading solar system
Upgrading solar system has unexpected traps. It is often better to scrap, use elsewhere, or attempt to sell that existing, and install a new one. This is particularly so with grid-connect systems and doing so with stand-alone systems is still tricky.
The Broome pool. The four 120 watt solar array can just be seen low down at the far (northern) end of the pool. The water nearby is a todal lagoon – that further back is the Indian Ocean. (The auto water level pipe is at pool right.) Pic: Author 2007.
The water pump for this 30,000 litre swimming pool is powered by four 100 watt solar modules. Pic. Solar Books.
Retaining or selling older solar modules is often possible. Good quality solar modules have a working life of 25-30 years (with only marginally less output). They are, however, likely to be incompatible with new ones. This is because solar module electrical characteristics have changed. It may be possible to overcome this – but too costly to be worthwhile. There can also be re problems with upgrading in that a number of legal (and Standards-related) requirements have changed. This relates also to the ways solar is installed.
A further reason for upgrading is that gas prices have escalated. It is now far cheaper to heat a home by using reverse-cycle air-conditioners in their heating mode. The top models now use only a quarter of the power of the same nominal wattage as an electric radiator or gas fire. This may seem impossible but is really so!
With grid-connect systems, in most areas, it now pays to install more solar than you use yourself. This increases feed-in rebates. It will also produce more power during times of lower solar input. Upgrading an existing solar system, however, has unexpected traps. There may, for example, be a limit on the excess amount. if so, the maximum is likely to be 6 -6.6 kW. Your installer can advise. read more…
Fuel cells for homes and properties
Fuel cells for homes and properties
Fuel cells for homes and properties provide clean silent electricity. High current prices hinder their acceptance, but this may soon change. Fuel cells enhance solar. Furthermore, they may all but eliminate our need for battery storage. Fuel cells hugely reduce harmful emissions.
Fuel cells for homes and properties provide clean quiet electricity. This article explains how, why and when they will be used. Fuel cells for homes and properties may all but eliminate battery storage. Moreover, fuel cells slash harmful emissions. This is a major bonus for all-electric cars.
The Panasonic fuel cell in the German Vitovalor product. Pic: Viessmann.
In 1839 Sir William Grove invented the first fuel cell. Petroleum was then found in abundance, resulting in fuel cells being overlooked. NASA later revived them.
Fuel cells for homes and properties – how fuel cells work
Fuel cells generate electricity. They do so via hydrogen reacting with oxygen. Heat, electricity and ultra-clean water-vapour results. Fuel cell chemistry is complex, but having no moving parts is a bonus. Fuel cells are easy to use, ultra-reliable and silent.
Hydrogen that fuel cells does not exist in free form. It can be produced from water, biomass, minerals and fossil fuels. Furthermore, it is readily produced from solar energy. Moreover, hydrogen is an energy multiplier and carrier. So, rather than using batteries, hydrogen can alternatively store energy. This is already being exploited (see below).
Fuel cells for homes and properties – hydrogen (how safe)
All fuels store energy. They have to be volatile. But unlike most fuels, hydrogen is not toxic. Furthermore, spilled hydrogen quickly evaporates. It leaves only tiny amounts of ultra-pure water.
Some quote the Hindenburg disaster. This airship used a huge volume of hydrogen contained within the airship’s outer skin. That skin was cellulose nitrate plus aluminium flakes. Rocket fuel uses the same products. That of the Hindenburg’s finally ignited.
Commercial hydrogen is stored in strong tanks. These are tested and certified accordingly. The risk is no higher than if containing any other fuel. read more…
Convert to your own all solar home
Convert to your own all solar home
This vital easy to read guide shows you how to convert to your own all solar home at minimal cost. You can readily do this between 50-degree latitudes north/south. This easy to read article shows that to to convert to your own all solar home can save you thousands of dollars.
This article shows how to convert to your own all solar home. Do that and you can slash your power bills to virtually zero overnight. Our current home north of Sydney (Australia), when bought in 2000, drew over 35-kilowatt/hours a day. Whilst over twice that typical it did not worry us. We knew how to slash that by 30% or more overnight at zero cost. How you can do this too is outlined below. It is your first step to having your all solar home. It needs only a tiny, but vital, change in what you and your family do but it can save you thousands of dollars! From there you continue to reduce energy use – and only when that is done do you start thinking of how much solar you need.
Our all-solar home in Church Point, NSW. Pic. rvbooks.com.au
The above is not how professional solar installers work. They may suggest a change to LEDs but otherwise calculate the energy you use, add a bit on top, and advise solar capacity accordingly. It is a quick and easy approach, but you will need a huge amount of solar to avoid paying power bills.
Convert to your own all solar home – wall warts suck!
Wall warts are those little grey or black boxes plugged into your power outlets. They enable you to turn off your lights, radio, TV etc by their remote controls. A typical home has 20 to 40 of them. Each draws only a tiny amount of power but do that day and night. Many draw far more power than whatever they control.
These wall warts typically suck a third or so of total electricity usage! Fixing the issue is simple. Turn off everything at all switch – never by the remote control alone.
Convert to your own all solar home – change the light globes
A further major energy user is incandescent light globes. They create a great deal of heat and some light. Many countries ban their sales. Fluorescent globes draw less, but the latest LEDs (Light Emitting Diodes) use only 20% or so of the energy of those incandescent globes and 50% of fluorescent globes. They cost more initially but have a far longer lifespan – typically many years. Many directly replace your existing globes. Almost all are available in warm white as well as the cooler light often used in kitchens. You can use some with existing wall dimmers. You can buy LEDs in Edison screw as well as for bayonet fittings.
This Philips 230 volt Edison screw LED produces 4-5 times more light than its incandescent predecessor.
Changing the light globes should be your next step when you convert to your own all solar home. You do need to spend money to do, but that which you saving over time is huge. Hint: You can often buy LED globes in bulk at a major discount.
Convert to your own all solar home – heating
Many homes have gas or electric radiator heating. It is far more efficient to heat your home by using reverse-cycle air-conditioners, using their heating cycle. By utilising so-called ‘latent heat’ this provides up to four times more heat for the same amount of electricity as electric radiators of the same nominal wattage.
Reverse-cycle air-conditioners vary in efficiency. All reveal their so-called CoP (coefficient of performance): in effect, the amount of cooling or heating (in watts) for the watts actually drawn. Top units (such as Daiken) have a CoP of about 4.0. The higher the CoP the more efficient it is.
If your home has heavy walls, heat it during the day (if/when solar is available). Reduce the heat setting during the evening.
Convert to your own all solar home – refrigerators
Refrigerator efficiency improved considerably from 2000 onward – and in many cases dramatically around 2014. Consider replacing any made prior to 2014 and do replace if pre-2000.
Be aware that the larger the fridge the more efficient it is (pro rata its volume). For this reason, never have two small fridges. One of that same total volume will use only a quarter to a third more electricity – not twice.
Swimming pool pumps
A typical swimming pool pump uses a huge amount of power. Here too, you can make truly major savings. If you have ample sun, consider installing a small stand-alone (48-volt dc) solar array directly running a 48-volt input dc brushless dc pump. You usually need no batteries as ample water is circulated whenever there is some sun. How to do this is explained in our book Solar Success.
Irrigation
You can save power used for pumping by knowing that water truly resists being pumped. Doubling pipe size costs little – but reduces the energy used by the pump no less than five times. This can make a huge difference even with small irrigation systems. Here again, see Solar Success.
Our present home
Our present home has 6 kilowatts of solar plus a 14 kilowatt/hour Tesla battery. The solar array produces 20 to 45 kilowatt/hours a day- and we currently use only 9-11 kilowatt/hours a day. The surplus is sold to the electricity grid (for 20 cents per kilowatt/hour – about A$730 a year). (We plan later to buy an all-electric Mercedes car and use that surplus to run it.)
See also: our previous -self-designed and built stand-alone system in Australia’s remote north-west Kimberley at https://solbsau.centrails.com/ensuring-successful-solar/
About our books
Our books include Solar Success (for home and property systems), Solar That Really Works! (for boats, cabins, travel trailers and motorhomes), and Caravan & Motorhome Electrics (that covers all aspects in depth). They are available in both digital and printed form.
Overweight RVs – a police point of view
by Collyn Rivers
An interview with Sergeant Graeme Shenton
Overweight RVs – a police point of view is a précis of my discussion with Sergeant Graeme Shenton about a major roadside check of the extent of overladen RVs. Most rigs checked were travel trailers.
RV Books: Do RV owners see overloading as a safety issue?
Sgt. Shenton: Travel trailer owners appear to accept overweight travel trailers are a risk. They also accept that police should actively check offenders.
RV Books: Is there not a further problem that vehicles used to tow travel trailers are far too light? They have increasing power, but lighter construction?
Overweight RVs – a police point of view –travel trailers too heavy
Sgt. Shenton: Travel trailers have become larger. Many 3.5 tonnes or more. The vehicles used to tow them are too light to tow such weight. In my opinion, the ‘tail wagging the dog’ effect contributes to travel trailer instability. It causes crashes and roll-overs.
RV Books: Do you have any data about the number of accidents resulting in travel trailer rollovers?
Sgt. Shenton: Of ‘rollovers’ alone, one insurer (that has 30% of the market) advises it has had well over 100 claims a year during the past 4.5 years. If ‘loss of control’ accidents is included, it’s multiple thousands.
RV Books: When did you start publicising details of weighing – was there any negative reaction?
Sgt. Shenton: The concept of what became overweight RVs – a police point of view was in May 2016 and related to rigs being checked at the Cann River weighbridge. There were no negative reactions. Photographs taken there [by Martin Ledwich] were viewed many thousands of times for months thereafter. It was very gratifying as it focused attention on safety issues.
Overweight RVs – a police point of view – overweight issues
RV Books: I recollect your later check (January 2017 in East Gippsland) resulted in some surprises. This because many of those attending had been invited. They knew their rigs would be weighed.
Sgt. Shenton: Indeed! It surprised us too! We had made it widely known that our check was being made. Also that its aim was to gather information. We weighed 71 rigs. Of those, 41 were overweight in one (or more ratings). A surprise was that most owners had some idea of their legally maximum weight. Only three, however, knew what their rigs actually weighed. Only two knew all the applicable ratings.
RV Books: For overweight RVs – a police point of view – were many seriously overweight?
Sgt. Shenton: Five (travel trailers) were overweight by more than 20%.
Overweight RVs – a police point of view – owner reactions
RV Books: What reaction did you receive when owners were made aware of their travel trailer and tow ball weight?
Sgt. Shenton: Surprise at the actual weight. Also that they had so substantially underestimated it.
RV Books: Again for overweight RVs – a police point of view did you also check the tow vehicles?
Sgt Shenton. No, it was felt better to weigh as many travel trailers as possible. It was clearly obvious, though, that many of the tow vehicles too were overladen. We advised owners of how to reduce that weight. We also advised of the [adverse] effects of weight, and its distribution, on stability.
RV Books: The results seem to indicate that many RV owners have no idea what their rig weighs!
Sgt. Shenton: It certainly showed their knowledge of weights and (legal) ratings to be minimal. Also that this lack of knowledge, and its safety implications, requires further attention. It is of major concern that most drivers have little idea of what their rigs actually weigh.
There’s also a problem, primarily with travel trailers. The Compliance plate does not always show the true Tare weight. That can lead owners into loading their RVs beyond the legal maximum.
RV Books: To what extent do you feel that such overloading is causing RVs to be unsafe?
Sgt. Shenton: It is difficult to quantify. It seems logical exceeding permitted limits will increase the possibility of having an accident. It will also increase its severity.
Owner reactions
RV Books: Did you experience any hostility to Overweight RVs – a police point of view operations?
Sgt Shenton: Next to none. RV owners seemed keen to know about matters vital to safe usage. Not just for themselves but to pass on to others.
RV Books: We believe tow courses for new travel trailer buyers towing drivers should be obligatory. Do you have any views about this?
Sgt. Shenton: Yes, very much so. Such courses are commercially available. They are supported by the Australian Government. Furthermore, it is a nationally recognised qualification.
RV Books: Any further recommendations for our readers?
Sgt. Shenton: I feel that education is more important than enforcement. I’d like to see more use of transport authority weighbridges – but many are closed much of the year. Also, that driver education is encouraged by travel trailer dealers.
Also important is that RV vendors stop declaring incorrect Tare Mass on compliance plates.
RV Books: Thank you very much for making this invaluable information available. It is greatly appreciated.
NOTE
Sergeant Shenton was an Acting Sergeant when the original inspections were conducted. He was subsequently promoted. His work is being extended to other states and jurisdictions. They have generally similar results.
Have portable solar in your rented home
Have portable solar in your rented home
You can easily have portable solar in your rented home. Here’s how to do it simply, safely, legally and cheaply using readily bought parts.
You can easily have portable solar in your rented home. Here’s how to do it simply, safely, legally and cheaply using readily bought parts. Doing so requires space that faces the sun for some daylight hours year-round. It works best within 50 degrees latitude north or south. Use high efficiency (plus 20%) solar modules to maximise input. You must not connect the system to any fixed mains wiring. This precludes using existing lighting. Use portable light fittings instead. Also, slash lighting cost by fitting LEDs. You take all that when you leave.
Here’s how
Group electrical units that you use at much the same time. Examples include a home office, child’s study or entertainment centre. Depending on individual needs, make-up one or more systems, each accepting solar input. You can do this by using readily available portable inverter/chargers and battery packs. Grouped electrical devices connect to a multiple power board that can switch each socket individually. The solar unit then powers that board. If solar is adequate it can be used to power a second or more system.
Where and what you can use
Top solar modules produce about 180-200 watts a square metre. In most cases, your solar input is thus limited to about 500 watts. This will be a probable 1500 – 3000-watt hours/day if north facing. This runs computer systems plus LED lights, and good LED TVs up to 60 cm or so. It will not run air con, nor heating/cooking appliances.
All that’s needed is stocked by solar equipment suppliers. The parts needed are used also in travel trailers and motorhomes. They readily interconnect. As pictured above, inverter-chargers combine all required apart from the battery. They are often buyable secondhand at bargain prices.
My books Solar That Really Works! and Solar Success provides ample background for people considering this.
Caravan nose weight – it’s vital for safe towing
by Collyn Rivers
Travel Trailer Nose Weight
Optimising travel trailer nose weight is vital for safe towing. RV Books’ Collyn Rivers shows why, and how to know what it should really be.
A billiard cue thrown light-end first rapidly changes ends. It becomes heavy-end first. Likewise, unless travel trailers are nose-heavy, they try to do the same.
Travel trailer nose weight, however, levers up the front of the tow vehicle. This reduces weight on its front tyres, that reduces their ‘cornering power’, i.e, it tends to oppose it moving in any but a straight line. This, (to put it mildly) is not desirable. It is even less so if needing to swerve to avoid a collision.
Travel trailer nose weight
Early Australian-made travel trailers were typically 4-5 metres long. They weighed 1000-1200 kg. Most had centre kitchens and thus (usefully) centre-heavy. Few were towed above 80 km/h. Keeping them reasonably stable required a nose weight of 7%-10%.
Particularly from 2015, tow vehicles of 2-2.5 tonne led to maker producing longer and heavier twin-axle travel trailers. Many such travel trailers well exceed their tow vehicle’s weight. Furthermore, many are towed at well over 100 km/h.
Travel trailer length
Within reason, a travel trailer‘s weight is less of an issue than its length. And particularly where weight is distributed along that length. The closer that weight is to the axle/s the better. Ideally, the A-frame should carry no load. Furthermore (and vital) nothing heavy should be at its rear. In addition, personal loading should be likewise. If your travel trailer is like that, a nose weight of 7% should suffice.
The effect of weight depends on where it is located. Pic: original source unknown.
The ongoing quest for reducing emissions includes reducing vehicle weight. That, as a result, reduced their allowable hitch weight. UK and EU travel trailer makers accordingly produced lighter travel trailers. Most weigh about 40% less per metre than the local product. They have minimal rear-end weight. Most have a nose weight of around 5%. European research, however, indicates that 6-7% is preferable.
In Australia, despite now lighter towing vehicles, most new travel trailers remain 6-7 metres long. They typically weigh 2 to 2.4 tonne unladen. To enable them to be towed by vehicles typically much lighter, unladen nose weights are, however, now around 4%.
This now very low nose weight is of concern. This is because there is a long-proven correlation between a travel trailer‘s nose weight and the road speed at which it is likely to sway. The lower the nose weight, the lower that speed.
What makers suggest
Some travel trailer makers have ceased recommending nose weight. Many quote the unladen tow ball weight only. Notwithstanding that such weight may be well below optimum, it is only possible (legally), to advise buyers to follow maker recommendations. RV Books, however, does not necessarily endorse such recommendations.
Where no maker recommends otherwise, and where the tow vehicle allows it, use 8%-10% nose weight. For EU-style travel trailers use 6%-8%.
Off-road travel trailer nose weight
It is very rare to see a heavy ‘off-road travel trailer‘ being driven truly off-road. Many Travel trailers, however, buy such travel trailers assuming that they are better made. Some such travel trailers, however, weigh over 3.5 tonne. These really do need at least 2500 kg (5500 lb) nose weight (and preferably 3500 kg [7715 lb]). If buying, I recommend one no longer than 5 metres.
It is not feasible to suggest an off-road travel trailer‘s nose weight – except it should as much as the tow vehicle, travel trailer and tow hitch maker allows. Or, if lower, not towed above 80 km/h.
Weight Distribution Hitches (WDHs)
Unless towed by a vehicle that’s heavier, a WDH is usually required. Adjusting this to correct only 50% or so of nose weight assists towing stability. See weight-distribution-hitch-setting-up.
‘You want your money back!?’ – I told you it could be towed by your pick-up truck. I never said you should! Pic: agcoauto
How to measure travel trailer nose weight
Bathroom scales typically weigh up to 185 kg. To weigh more than that (using such scales) see: https://hildstrom.com/projects/2011/07/tonguescale/index.html
Note: It is technically correct to refer to nose mass (rather than weight). For the purposes of this article, however, the two may be seen as identical.
For an overall view see also:
https://solbsau.centrails.com/reducing-caravan-sway/
https://solbsau.centrails.com/making-caravans-stable/
https://solbsau.centrails.com/caravan-and-tow-vehicle-dynamics/
https://solbsau.centrails.com/fifth-wheel-caravans-safer/
Collyn Rivers’ in-depth books cover every aspect of camper-trailer, travel trailer and motorhome buying, design, building and use. They include the Caravan & Motorhome Book, the Camper Trailer Book and Caravan & Motorhome Electrics, Solar is covered in Solar That Really Works, for cabins and RVs. Solar Success is for homes and properties.
The Caravan & Motorhome Book covers travel trailer stability in depth.
If you find this article of value, please assist others by posting this Link on related travel trailer forum queries.
My articles in this area primarily summarize current thinking. They stem from my interest and involvement while employed by Vauxhall/Bedford’s Research Dept in the 1950s, and particularly by the influence of Maurice Olley.
Maurice Olley was born in Yorkshire in the late-1800s. Following time as Rolls-Royce’s Chief Engineer, he worked with General Motors Research Division. He later returned to Vauxhall Motors (UK). I was privileged to attend his lectures during my years at Vauxhall Motors Chaul End Research Centre.
How to stop paying for electricity
How to stop paying for electricity
How to stop paying for electricity is easy. This article shows how. Going almost totally off-grid is more affordable than ever. Now the electricity provider pays us. You can do the same – here’s how.
Solar is now cheap
We always wanted to stop paying for electricity, and now we virtually have. It is getting easier to free yourself from dependence on the grid.
Many governments subsidise home solar. Most buyers, however, purchase only small systems: typically 1.5 or 2.4 kW (kilowatts). These, in Australia in early 2019 cost A$2500 -A$3000 installed. This helps reduce existing bills, but increasing solar capacity is truly worth considering.
Our (NSW government) subsidised 6 kW system cost us A$4350. It produces an average of 25-40 kilowatt hours a day. We initially paid the electricity supplier A$ 0.27 per kW/h for about three hours each night. We sold the daytime surplus (of an averaged 17 kWh/day) for a contracted 20 cents per kilowatt-hour for two years. This brought in about A$1200 a year. The initial cost of installation was A$4500. The result was then free power plus an increasing yearly income inside four years.
How to stop paying for electricity – adding battery backup to our solar array
As with many others, we prefer not to totally rely on grid-power – even as a back-up. Having self-built our own 3.8 kW stand-alone system in Australia’s Kimberley, we knew that do this is totally feasible. But unless electricity exceeds about $1 a kilowatt/hour it is currently not a money-saving thing to do. Whilst going totally off-grid still appeals we settled on a compromise that is proving very satisfying. read more…
Inverters for Homes and Properties
Inverters for Homes and Properties
How to choose inverters for homes and properties. Inverters convert the solar battery output into 110 or 230-volt alternating current. It is all-but-essential to use one. Using only 12-48 volts is too limiting for all but basic cabins.
Two Outback Power inverters are interconnected. Pic: Outback Power
User only inverters marketed as sine-wave (not modified sine wave etc). High-quality sine-wave inverters produce electricity that is ‘cleaner’ than the average grid supply. Other types do not. They may wreck sensitive electronics. There are two main types of sine-wave inverter:
Transformer-based inverters
Those transformer-based are bulky and heavy. This is rarely an issue for homes and properties. Their major plus is inherent overload capacity. Tools and domestic appliances draw two/three times they’re running current whilst starting. Transformer units handle this with ease. Some produce twice or more their output rating for 30 minutes or so.
Transformer-based inverters up to 1500 watts will run from 12 volts. Those for up to 3000 watts require a 24-volt inverter. Anything over that needs 48 volts.
Only a few (e.g. Outback Power units) can be parallel-connected to increase output. This ability is uncommon. If you need, obtain written assurance of feasibility.
Switch-mode inverters
Switch-mode inverters are smaller and lighter. Few, however, have overload capacity. Most only sustain their rated output for a few seconds. The better quality units sustain 80% (of rated output) for constant use. Some, however, may only sustain 50%. Switch-mode inverters work best for loads that draw no excess starting energy. These are rare. Air-compressors draw many times they’re running current whilst starting.
In Solar Books opinion, the best inverters for home and properties are those transformer-based.
Inverters involve complex technology. Our book, Solar Success explains inverters for homes and properties. Solar That Really Works! does likewise for boats, cabins and RVs. The top-selling Caravan & Motorhome Electrics covers inverters in detail. All our books are in digital or print versions. Digital ones can be bought right now. Click on a title (above). Print versions are stocked by all Jaycar stores in Australia and New Zealand and most Australian book shops. They are also available via email (and post) from booktopia.com.au
Grid connect solar problems – what vendors may not reveal
Grid connect solar problems
Grid connect solar problems include, false promotion and vendor claims, incompetent installation etc. Here’s what vendors may not tell you.
Q. Must solar panels be at an exact angle?
A local installer says my existing 1.5 kW system’s modules must be at exactly the same angle as my latitude. They are only a few degrees out). He say he can fix them for $1000 – so most days they’ll produce a lot more. Is this a scam?
A. Yes. He’s after your money!. In most areas plus/minus 5º makes less than 1% or so change. It may, however, result in a bit more in summer than winter – or vice versa. Less than that will make next to no change. It is, however, desirable to have them face more or less into the sun around midday. But, here again a few degrees does not matter.
Q Grid connect solar problems – do I need after-sales service?
My installer seeks $250 a year for ‘servicing and tuning’ my 1.5 kW grid connect system. Do I really need that?
A. This too is a scam. Installed solar needs no servicing, let alone ‘tuning’. Unless the modules are truly dirty, there is likewise no need to clean them. Occasional rain does the job. Our own grid connect systems (north of Sydney) remains unwashed since 2010. There is no measurable loss.
Q. Grid connect solar problems – do I need a tracking system?
I live in the south of Australia where the sun is much ‘lower in the sky’ in winter. My installer advise using a $5000 (plus $1000 installation) tracking system for my proposed 1.5 kW grid-connect system. He claims it will save the amount of solar capacity otherwise needed by about 30%. Is this true?
A. What he claims is true. But what he has not revealed is a lot!
Tracking systems are costly and need ongoing servicing. It is hugely cheaper to accept that loss. You can add another 450 watts more solar capacity for a probable $1250! And zero maintenance. Find another installer.
Q. Grid connect solar problems – how do I work out the grid-connect size I need?
I’d like to install enough grid-connect solar to halve my existing power bill. Installers say they need to calculate how much electricity is used and quote accordingly. Is there any way I can tell if they are selling me more than I need.
A. This is routine practice. The best way to start, however, is to reduce existing usage. We slashed the previous owner’s 31 kWh a day to 4.1 kWh a day summer and 6 kWh in winter.
It costs some money up front, however, savings are huge over time. That alone will fix that ‘halving’ you seek. Adding solar then – and only then, will drop it yet further. It is not feasible to explain how in an article. The first third of my book Solar Success shows exactly how to do it. It includes actual examples (including our own). Unless you do this, the installer will scale the system to existing usage. read more…
RV Solar and Alternator Charging
RV Solar and Alternator Charging
You can make RV solar and alternator charging work. It is complex on post-2014 vehicles. This article explains how.
How RV solar and alternator charging works
A travel trailer or motorhome battery charges by connecting it across it a source that has a voltage that is higher than that battery has at the time. That battery neither knows nor cares whether that charge is from one source or several. Those sources must all be of closely similar voltage. Ideally, they are identical. If not, the battery will draw mostly from that with the highest voltage. Charging becomes complicated, however, once the battery/s approach full charge.
What happens then is that the controllers associated with each charging source mistake each other’s voltage for the battery. This may cause damaging overcharging. This is particularly so with AGM and LiFePO4 batteries. This applies also to simultaneous solar and generator charging. Do not attempt to do this yourself unless you know how. This explained in our book Caravan & Motorhome Electrics.
Suitable controllers for RV solar and alternator charging.
Most controllers sold for both solar and alternator charging, monitor both solar and alternator input but do not combine them. They switch to whichever has the higher input at the time. Solar Books recommends RV solar users to do likewise. This is particularly so with most vehicles made since 2010 or so and virtually all since 2014.
Issues with post-2014 RV solar and alternator charging
Prior to 2014 or so, vehicle alternators produced about 14.2 volts for some minutes after engine starting. This dropped to a more or less fixed 13.6 volts thereon. This, by and large, presented no issues for RV battery charging. Such alternators had a high enough voltage to charge a secondary battery in the vehicle to a usable level for leisure or auxiliary use. Ongoing emissions regulations however require minimising power usage. This (in 2014) extended yet further – to vehicle alternators of variable voltage. read more…
Solar Shadowing – reducing the losses
Solar Shadowing
Solar shadowing – reducing the losses is like you partially unblocking a water pipe. Partial solar shadowing reduces your losses proportionally. Except in extreme clouding, however, solar modules produce some output. During daylight it’s rare for you to have none.
Pic: solarbay.com.au
Solar Shadowing – reducing the losses – bypass diodes partially assist
Most 12-volt solar modules have 60 cells. Each cell is connected in a string. A totally shadowed cell produces no current. Blocking one affects all.
Basic modules supply the current of the least producing cell. To limit this, good quality modules have three strings. Each string has 20 cells. Furthermore, each string has a so-called ‘diode’. If activated, it carries current from unshaded strings. This assists, but is not a perfect solution. With only one cell shaded, output is slashed one-third. Furthermore, diodes are not reliable. One diode failing will prevent associated strings working.
The ideal is a diode across each cell. Doing so, however, is costly. Worse, diodes fail more often than cells. Reliability is reduced.
Solar Shadowing – reducing the losses – the more effective ways
In basic systems, the lowest cell output limits your overall output. With multiple modules, shadowing one limits output of all. The loss is confined to the area shaded.
Power Optimisers
Power optimisers attach to existing solar modules. They maximise energy. Power optimisers also eliminate power mismatch. They decrease shadowing losses. Such optimisers can be built into solar modules. Or fitted separately. The concept works well.
Pic: Enphase micro-inverter (power optimiser)
Solar Shadowing – reducing the losses
Our books cover shadowing issues in depth. Solar That Really Works! is for cabins and RVs. Solar Success is for homes and properties. Caravan & Motorhome Electrics covers RV solar and general electrics. All are available in digital or print form. Moreover, our books also cover legal issues. Furthermore, you can download our digital versions right now. Click on the books’ title (above). Print versions are stocked by all Jaycar stores. You can also buy them (from anywhere) from booktopia.com.au/
Solar Modules for Homes and Properties
Solar Modules for Homes and Properties
This article shows how to know power output from solar modules for homes and properties. It shows how to optimise it for winter or summer.
Top quality solar modules catch 18% to 20% of the solar energy available. This is typically 140 watts-180 watts per square metre in full sun from about 10 am to 2 pm. Input tapers off before and after. Such modules are priced accordingly. Buy only top quality unless you have ample space for those cheaper but less efficient.
Solar modules for homes and properties – which way to face?
For maximum daily input, solar modules should face directly into the sun at mid-day: due North or due South. This is not always feasible, but the loss is not appreciable. Even if facing away from the sun at midday, you will still have worthwhile input. If in such situations (and you have room) simply add more solar modules. Their cost now is so low it will not cost much more.
Solar modules for homes and properties – at what vertical angle?
Most books and articles advise to tilt them at the same angle as your latitude (e.g about 33 degrees for Sydney, Australia). Errors of 10 or so degrees, however, make little difference in the yearly total. It is possible to increase winter input (at the expense of summer input) by tilting the modules more upright. Likewise, increasing summer input by having them closer to flat. At one time some people had them adjustable – but this is rarely feasible (or safe) if roof-mounted. But here again, if space is available, simply add solar capacity. This may require a larger solar regulator – it cannot ‘overload’ the existing regulator but it blocks current input in excess of its maximum rating. read more…
Travel trailer design need for change
by Collyn Rivers
Travel Trailer Design need for change
The need for travel trailer design change is increasingly necessary. Australia has two main and seemingly interdependent travel trailer industries. One makes travel trailers of stability varying from a few that are excellent, to some that should not be on the market. The other travel trailer industry makes devices (of equally varying effectiveness) intended to increase travel trailer stability. Far from all involved, however, appear to understand the basic laws of physics involved. Or they assume they are somehow immune from them.
With a few rare exceptions, there is a travel trailer design need for change. There is also a need for travel trailer owners to realise to understand, or at least accept, that a conventional travel trailer has inherent stability issues.
So-called travel trailer stability aids have fundamental limitations. An example is any form of friction-only stabiliser. The limitation here is that frictional force is a constant: the sway forces it must control, however, increase with the square of the travel trailers) speed. A sway force which might be trivial at 25 km/h is not four times greater at 100 km/h. It is sixteen times greater. One published paper (re friction-only stabilisers) states the effect of its damping at 100 km/h ‘is less than 1%’.
Known for over 500 years
The basic understanding of the mechanics and physics involved in moving objects have been known and understood for over 500 years. Despite this, some of today’s travel trailers embody principles known as unsound even back then. Around 1480, and as with today’s travel trailers, Leonardo da Vinci (in his ‘Codex Flight’) noted that ‘a body in motion desires to maintain its course in the line from which it started’.
Long travel trailers, particularly those with rear-hung spare wheels, are prone to vertical and horizontal see-saw effects. Yet Galileo (around 1600) explained in detail why and how this happens. Known technically as ‘moments along a beam’ it was raised again by Leibniz in 1684.
In 1686, Isaac Newton ‘noted that a ‘body in motion would stay in the same motion unless acted upon by another force’. Despite this basic knowledge (taught in elementary school science), many travel trailer makers and travel trailer owners seem unaware of, overlook or grossly underestimate that ‘another force’. That force can be a strong side wind-gust, strong emergency swerving etc. Or the result of seriously bad travel trailer loading.
Overhung tow hitches cause jack-knifing
Until 1920 or so, most heavy transport trailers were towed (as are today’s travel trailers) via hitches overhanging the rear of the towing vehicles. This worked well initially. Increasingly powerful engines, however, soon enabled speeds exceeding 20 mph (about 32 km/h). Jack-knifing and rollovers then became increasingly common. This was less so in the UK. Trucks there were limited to 20 mph (32 km/h) until 1957 and then to 30 mph (48 km/h) in 1957. It remained at that until 2015.
In 1920, the USA’s Fruehauf transport company realised that jack-knifing’s cause was that tow hitch overhang. That overhung hitch does not just enable a central-axled trailer to yaw. It causes it to yaw. Fruehauf accordingly located the tow hitch directly above the tow vehicles rear axle/s. Eliminating that hitch overhang solved the problem. The resultant (now-stable) so-called ‘articulated’ rigs (their hitch is often called a ‘fifth wheel’) have been used for heavy goods road transport ever since.
Many Americans then used fifth-wheel hitch travel trailers. The first known was in 1917.
The first-known recreational fifth-wheeler: the 1917 Adams motor bungalow. Pic: Glenn Curtiss Museum.
Many later fifth-wheelers were towed by modified chauffeur-driven coupes. The owner and passengers travelled in the fifth-wheeler.
The 1932 Curtiss Aerocar. The tow vehicle is a 1932 Graham-Paige. This rig was used by financier Hugh McDonald as a mobile office for his daily journey to and from New York. It had a full kitchen and bathroom. His staff included an on-board chef. Pic: HET National Automobile Museum, Steuweg, 8 NL.
Apart from the USA, most other countries opted for travel trailers towed via an overhung hitch. But right from the beginning, as in the early transport industry, jack-knifing was only too common. It was reported in early travel trailer magazines.
Travel trailer design – limiting their length
For many years the main emphasis for optimising tow vehicle and travel trailer stability has been on weight. In particular, a laden travel trailer should not weigh more than its laden tow vehicle. That was and still is important.
Now, however, the major limiting factor has become travel trailer length. As rollover after rollover shows, it is long twin-axled travel trailers that are now mostly involved. Many have front-located water tanks – that result in tow ball mass varying as water is used.
Many recent travel trailer rollovers are off long travel trailers with front-located water tanks
Long so-called ‘travel trailers’ are common in the USA. Most, however, towed by vehicles that are heavier and longer than used in Australia. Many are made by Airstream, a company that has long understood how to optimise trailer stability. The spare wheel, for example, is located under the chassis, to the front of the axles. Most US travel trailers use the heavy, but ultra-effective anti-sway Hensley hitch. This, in effect, uses a trapezoidal linkage that projects the virtual position of the tow ball closer to the tow vehicle’s rear axle.
Travel trailer design – the see-saw effect
A conventional travel trailer is like a see-saw. Its wheels form the pivot. As with a see-saw, the effect of weight on a travel trailer depends on how far weight is from its axle/s. An 80 kg (175 lb) adult a metre in front of the axle/s is readily balanced by a 30 kg (66 lb) child at the travel trailer‘s far end. Because of this effect, a 20 kg (44 lb) spare wheel on the rear of a seven-metre travel trailer is an effective 70 kg (155 lb) or so. Some travel trailers have two such spare wheels. If that travel trailer pitches or yaws, the effective weight of those wheels is magnified yet more. They initially strongly resist that movement, but once that (so-called inertia) is overcome, they then equally resist ceasing it.
This spare wheel ‘end-heavy’ issue is often raised on travel trailer forums. It attracts naive responses to the effect that all is fine – ‘the travel trailer has been designed accordingly’. Physics, however, does not work like that. Do some travel trailer makers not realise this? Or do they simply do not care about its inherently adverse effects?
Travel trailer stability standards
No Australian Standard currently addresses this issue. The national trailer standard, VSB1, states ‘There are no specific body structural requirements, but the trailer must be safe and fit for purpose.’ VSB1 suggests as a minimum: that the manufacturer should be able to demonstrate that the structure is capable of supporting the designed payload with a ‘safety factor of at least three for highway use and a safety factor of five for off-road use.’ It does not comment on stability. Nor do any other Australian Standards or regulations.
Nor is travel trailer stability mentioned in the travel trailer industry Association of Australia Ltd’s own RVMAP Code of Practice. It is almost entirely concerned about building the product. Page 48 of that industry’s travel trailer towing guide, shows a travel trailer that has two bicycles and a motorcycle on the rear of a travel trailer. It comments only that they obscure the number plate. This is an extraordinary sense of priority. https://caravantowingguide.com.au/pdf/TowingGuide2018.pdf
The SAE J2807 standard
Travel trailer stability is addressed in the USA’s J2807. Initiated by Toyota in 2010 this (now) SAE Standard is followed by all US and the top three Japanese vehicle makers. It sets out the performance requirements for determining tow vehicle gross combination weight rating, and trailer weight rating.
The SAE J2807 standard covers all vehicle and trailer combinations of a combined laden weight up to 5896 kg (13,000 lbs). The standard sets out tow-vehicle requirement for (combination) vehicle requirements for acceleration, hill climbing, understeer, trailer sway response and braking (at maximum legal laden weight). It also covers the tow hitch and related components. The main handling requirements relate to ‘cornering power’. It also covers the tow vehicle’s reduction inherent cornering power (of about 25%) when using a weight distributing hitch.
Factors affecting stability
A travel trailer and tow vehicle’s stability is co-dependent.
Assuming correct loading and tow ball mass, excess caravan length is now the major cause of travel trailer instability. Weight, if centralised, and not excessive, is less of an issue.
Critical speed
A reasonably stable travel trailer is likely to become unstable if its tow vehicle is lighter or much shorter. And/or that tow vehicle has too low air pressure in its rear tyres. Or the travel trailer has too low tow ball mass.
For any combination of travel trailer and tow vehicle (and their loading), there is a critical speed. That critical speed is unique to each rig. It is related to many factors. These particularly include tow ball mass and travel trailer length and loading. The lower the tow ball mass the lower that critical speed. For most Australian rigs that speed is likely to be a little over 100 km/h. For some rigs, it will be below 100 km/h.
The issue of critical speed is often misunderstood. It does not follow that the rig will become unstable at, or above that speed. If towing at or above that critical speed, however, jack-knifing is far more probable in the event of an emergency swerve (or strong side-wind gusts). There is no currently-known way of establishing a rig’s critical speed (apart from wrecking it by testing) but the risk is far less by never exceeding 100 km/h. Forum dash-cam videos show many rigs beginning to jack-knife while overtaking heavy transport vehicles. As such vehicles travel at 100 km/h wherever possible, it is all but certain that most rigs were thus well exceeding 100 km/h.
Adverse effects of a weight distributing hitch
The critical speed is lowered if a weight distributing hitch (WDH) is used. The tighter that hitch the lower that critical speed. Here’s why.
Travel trailer towing reality is that if you need a WDH, you are imposing loads on a tow vehicle neither designed nor intended to withstand such loads.
A WDH compensates only for vertical loads. It does so by moving some tow ball weight from the tow vehicle’s rear tyres to its front tyres. The WDH cannot, however, reduce the side forces on those tyres when a travel trailer yaws or starts snaking. That lessened weight reduces their ability to cope with those side forces.
That WDH also reduces the tow vehicle’s intended and vital margin of understeer (that assists keep it stable). This may prejudice its handling in emergencies. It that tow vehicle loses all understeer at speed, it oversteers. If that happens jack-knifing is all-but-inevitable.
If using a WDH never adjust it to more than 50% correction. Contrary to ongoing forum mal-advice never adjust that WDH to have the travel trailer and tow vehicle level. When correctly adjusted, the caravan’s nose weight should cause the rear of the tow vehicle to be about 50 mm lower.
ow-ball weight
As with an arrow, it is vital that a travel trailer be nose-heavy. Tow ball weight is totally related to critical speed. The lower that tow ball weight – the lower that critical speed.
Following a general (2015) reduction in tow vehicle permitted tow ball weight, many local travel trailer makers then recommended only 4% tow ball weight – yet retaining virtually the identical design for which they previously recommended 8-10%. One astute observer described this as ‘brochure engineering’.
If all else remains equal, the speed at which a towed travel trailer is likely to sway is directly related to its tow ball weight. A travel trailer with low tow ball weight may not sway in normal driving. If it does, however, jack-knifing is far more likely. Any number of academic papers backed up by real-life testing confirms this. One USA study showed that a travel trailer with 4% tow ball weight had a critical speed of only 40 mph (about 64 km/h).
Travel trailer design – how to increase your rig’s stability
When buying a tow vehicle, choose one that has the maximum wheelbase (i.e. the distance between the front and rear axle). Furthermore, the shorter the rear overhang, the better. Also, when fully laden, that tow vehicle should weigh at least as much as the fully laden travel trailer.
Travel trailer length too is a vital factor. The longer the travel trailer, the less stable it is.
Use a tow hitch with the shortest possible overhang. Avoid even excess millimetres. If necessary have a machine-shop shorten that overhang. This usually involves simply drilling a new hole. It can be owner-done – but that hole must be only just large enough to provide a tight fit for the hitch securing bolt.
Do not lubricate the tow ball – its friction assists to limit sway. AL-KO has one that deliberately increases its friction. See Should I grease a tow ball.
When towing always load the tow vehicle to its legal maximum. If the fully-laden tow vehicle weighs less than the laden travel trailer, never exceed 100 km/h. In stating this, RV Books does not imply that towing such a weight at 100 km/h is safe.
Ensure, by weighing on a certified weighbridge, that your laden travel trailer is not overweight. Ongoing police checks show that almost all are – one was reported as being 400 kg (880 lb) over its legal maximum.
Never have anything heavy at the far rear of a travel trailer. That many travel trailers have spare wheels located there is contrary to the laws of physics – not just common sense. And why two spare wheels – when tow vehicles have only one – or do not even carry a spare wheel: many have a repair kit and an inflator.
Tyre pressures matter
Tow vehicle rear tyre pressures should be increased by 50-70 kPa (7-10 psi). Never increase front tyre pressures.
For reasons unclear, many travel trailer makers recommend using the maximum tyre pressures the tyre can withstand. The Caravan Council of Australia (and RV Books), however, strongly recommend using the tyre maker’s advised pressures for the travel trailer‘s laden weight.
Friction sway control
Friction-based sway control is effective, but only at low speed. This is because frictional forces remain constant. The sway forces they seek to control, however, increase by the square of the rig’s speed. At 100 km/h that friction is a close-to-useless 1%.
This inherent limitation is recognised in the UK and EU. There, the excellent AL-KO friction tow ball handles low to medium speed sway (yaw). Electronic stability control, however, acts (if needed) at higher speeds.
The AL-KO friction tow ball is very effective at low to medium towing speed. Pic: AL-KO UK.
Forum advice often misleads
Even good travel trailer design is rendered unstable if laden incorrectly. Here, some travel trailer forum advice seriously misleads. Travel trailers must be laden such that most of the weight (as possible) is close to (and preferably over) their axle/s. The required tow ball mass must only be achieved this way. Never adjust tow ball weight by adding sandbags etc at the very front.
Ultimately, travel trailer and tow vehicle behaviour depend on hand-sized rubber oval sections’ grip on the road. That ‘grip’ on dirt roads is on loose gravel (often corrugated). It is not unlike driving on ball bearings.
Never tow at over 100 km/h. Moreover, always bear in that travel trailer stability requires adequate tow ball weight. Furthermore, the lower that mass, the lower the speed that travel trailer is likely to sway.
That not generally realised is that it not so much travel trailer weight that matters. It is far more an issue of travel trailer length. Assuming sane loading, a two-tonne 14-foot (4.26 metres) travel trailer (some exist) is likely to be far more stable than a two-tonne 18-foot (about 5.5 metres) travel trailer.
Further information
This and associated travel trailer design issues are covered in depth in our (now top-selling book) Why Caravans Roll Over – and how to prevent it. As with all RV Books, it is available worldwide in eBook and paperback versions. They are obtainable directly from RV Books – or via outlets such as Amazon.com etc.
Blade fuse problems in travel trailers – they may burn or melt
by Collyn Rivers
Blade Fuse Problems
Blade fuse problems in travel trailers include fuses and fuse holders burning or melting. Fire risk is high because the fuses may continue to conduct. Ongoing current flow, however, may heat the fuse holder to burning point. This article by RV Books explains why and how to overcome the risk.
The blade fuse problems in travel trailers and motorhomes (and particularly boats and 4WDs used on beaches and camper trailers) are mostly caused by exposure or partial exposure to damp air, dirt and water. This corrodes the fuse holder and fuse contact surfaces.
Typical burnt blade fuse and holder. The fuse and fuse holder have melded into a solid lump. Pic: redarc.com.au
Blade fuse problems in travel trailers – fuse holder sizes
There are two main sizes of blade fuses and blade fuse holders. Most blade fuse problems in travel trailers arise if the smaller size fuses and fuse holders are used at currents greater than 15 amps. Some auto-electricians suggest 10 amps. All need protecting against damp or salty water, or atmospheres.
As can be seen, the larger size has substantially more contact area.
Blade fuse problems in travel trailers – quality issues
There can also be blade fuse problems in travel trailers with poor quality versions of the larger sizes fuses and holders. Some have next to no protection against even mild corrosion. This causes them to resist current flow, usually partially melting the holder but not necessarily the fuse. This results in a major risk of fire – especially if the wiring’s insulation is also burned. It may expose current-carrying copper that, then allows full battery current to flow – possibly to earth. This can and does cause fires.
Long term blade fuse problems in travel trailers are also indirectly caused by badly crimped cable lugs. The resultant poor contact eventually allows corrosion between the copper and the lug. Heat builds up, in turn heating up the blade fuse holder.
![Blade fuse problems in [cara_s] - they may burn or melt - electric vehicle batteries,book on batteries,electric car batteries,lithium ion batteries for electric cars,electric car battery technology,how long do electric car batteries last,electric vehicle battery life](https://solbsau.centrails.com/wp-content/uploads/2023/12/crimp-lug-badly-made.jpg "Blade fuse problems in [cara_s] - they may burn or melt 115")
This cable is only barely in contact with the crimp lug. Pic: original source unknown
A correctly formed crimp creates a cold weld. To achieve this it is 100% essential to use a proper crimping tool (as shown). Never use pliers or plier-like cheap crimping tools. A good ratchet type crimping tool, as shown below, forms that cold weld (i.e. an inter-molecular bond).
![Blade fuse problems in [cara_s] - they may burn or melt - electric vehicle batteries,book on batteries,electric car batteries,lithium ion batteries for electric cars,electric car battery technology,how long do electric car batteries last,electric vehicle battery life](https://solbsau.centrails.com/wp-content/uploads/2023/12/Crimping_tool_4_col_OK.jpg "Blade fuse problems in [cara_s] - they may burn or melt 116")
Use only a crimping tool like that shown: they are not cheap, but a badly crimped lug can set a travel trailer on fire! Pic: RV Books.
Blade fuse problems – the need for larger holders
Blade fuses. That most typically used is shown on the right. Use the Maxi version (left) for fuses of 10-15 amps and over.
The above fuses typically blow within 0.1-02 of a second at 600% of their rated value, and 1.0-2.0 seconds at 350% of their rated value. This is fine for protecting correctly specified cabling. Don’t, however, use any fuse that is higher rated than necessary.
Blade fuse problems in travel trailers – circuit breakers preferred
Ideally, replace high current blade fuse holders and fuse by manually re-settable dc circuit breakers. Those of totally reliable quality are stocked by marine electrical suppliers. Cheaper versions are available but are very temperature sensitive. This, in particular, is not an area to cut costs via eBay specials.
This a high-quality double pole dc circuit breaker. It protects both positive and negative cables. Pic: Carling Inc.
See also Circuit-Breakers-and-Fuses-in-RVs
Blade fuse problems in travel trailers – further information
Every aspect of RV electrics is covered in detail in my Caravan & Motorhome Electrics. Solar That Really Works is for cabins and RVs. Solar Success is for homes and properties. My other books are the Camper Trailer Book and the Caravan & Motorhome Book. For info more about the author Click on Bio.
Please post a LINK to this article on forums if you feel it would assist problems in this area.
Towing Without a WDH – Weight Distributing Hitch
by Collyn Rivers
Towing Without a WDH
Towing without a WDH (weight distributing hitch) is often feasible. A WDH is not needed if a tow vehicle’s laden weight is equal to or exceeds that of the laden travel trailer. Nor is a WDH needed for any trailer under 4 metres. A WDH may even cause instability.
Many RVers ask about towing without a WDH
A WDH attempts to compensate for issues better avoided. One is towing a laden travel trailer that exceeds the laden weight of whatever tows it. It is, for example, common to see 2500 kg (laden) dual-cab utes towing 3500 kg (7715 lb) travel trailers. Another is towing a travel trailer longer than six or so metres.
For on-road stability, a conventional travel trailer needs to be nose-heavy by 8-10% of its laden weight. When hitched to its tow vehicle that (typically 200-350 kg [440-770 lb]) pushes down the rear of that vehicle. In doing so, that levers up the front of the tow vehicle. This reduces the weight on the tow vehicle’s front tyres.
Where, however, that tow ball weight is comfortably within the laden tow vehicle’s payload, that front tyre weight reduction is too small to be an issue. It is, however, necessary to increase tow vehicle rear tyre pressure by 50-70 kPa (7-10 psi).
Some travel trailer owners fit a WDH because a sales-person advised it. Or by following misleading advise on Australian RVers forums. Fitting a WDH when not needed, can introduce unwanted issues. Towing without a WDH is preferred unless really needed.
Weight distribuing hitch. Pic. Jayco.
How a Weight Distributing Hitch works – and its unwanted effects
A Weight Distributing Hitch is, in effect, a springy light beam. By levering up the rear of the tow vehicle, it restores weight (down-force) from the tow vehicle’s rear tyres to its front tyres. While a good and useful concept, a WDH only counteracts tow ball downforce. By reducing tow vehicle rear tyre loading, those tyres become less able to counteract the yawing travel trailer‘s side forces on the rear of the tow vehicle.
The overall effect of a WDH is thus to reduce the rig’s ‘cornering power’. It does so by an appreciable amount. The USA’s J2807 Standard notes that ‘cornering power’ is reduced by 25%. Furthermore, those strong side-forces on the tow vehicle’s rear tyres may even cause those tyres to steer the tow vehicle. If that happens a jack-knife is virtually inevitable.
The above does not imply that the rig inevitably misbehaves at speed – but it is more likely to if ‘hit’ by a strong enough side force – such as wind gust. Or by cornering too fast. There is, however, a correlation between tow ball mass and safe speed. The lower that mass, the lower the safe speed. There is a very strong argument for that traditional 10%-12%. In the USA it is often 14%.
Towing Without a WDH – Summary
Fitting a WDH to a rig that does not need one is not only pointless. It introduces issues that do not exist without one. Towing without a WDH is feasible if the laden travel trailer weighs the same or less than the laden tow vehicle. Towing without a WDH is also feasible for correctly laden travel trailers less than six or so metres (about 20 feet).
If the weight issue is only minor, towing without a WDH is feasible by carrying the travel trailer’s spare wheel in the tow vehicle.
A full explanation of Towing Without a Weight Distributing Hitch (WDH) is feasible is in our book Why Caravans Roll Over – and how to prevent it.
Travel trailer suspension – it is mostly misunderstood
by Collyn Rivers
Travel Trailer Suspension
Travel trailer suspension has requirements that are very different from tow vehicles. This is only too often misunderstood. Here’s why and what it should be.
Travel trailer suspension basics
Were roads totally smooth, there would be no need for sprung travel trailer suspension. Most roads, however, are far from that. Even trains on smooth rails need springing. Travel trailer wheels must traverse bumps, holes and sometimes corrugation. They must do so without damaging the travel trailer and that carried in it.
The suspension is speed-related. Road shocks forces increase by the square of the speed. For instance, such shocks at 60 km/h are four times harder than at 30 km/h. At 100 km/h it’s over ten times as hard.
The effects are more severe than many owners suspect.
Jayco independent travel trailer suspension
How hard and how often
At 60 km/h, a bump one metre wide is crossed in a sixteenth of a second. It is not a gentle rise and fall. The wheel and axle are belted upward, compressing the associated spring/s. The heavier the wheels, tyres and moving bits of suspension (relative to that sprung) the greater the shock energy.
Whatever the springing form, it acts as a strong bow. It momentarily stores energy. The instant a wheel has passed over the bump, that spring instantly releases its pent-up energy. This jackhammers that wheel, tyre and axle back down. Unless slowed, it smashes wheel and tyre onto the road. The impact forces are taken via its wheel studs. Over corrugation, this happens about 1300 times per kilometre. And, likewise, per wheel.
Sprung suspension must dampen that downward release. This is typically done by friction (thus turning it into heat).
Travel trailer suspension – energy damping the primary need
With leaf springs, as compressing spring leaves slide (slightly) between each other, friction is caused. This only happens, however on the axles upward travel. As compression suddenly releases, there is no friction to dampen that movement: the spring leaves are no longer pressed together.
Early carriage makers knew all this by 1800 or so. They understood that, if spring movement is damped by friction, spring energy is released as heat. By binding the leaves tightly with strong leather thongs they increased inter-leaf friction. (Some vintage car owners still do). Today’s crude upper clamp only vaguely holds the leaves together.
Early carriage suspension was surprisingly sophisticated.
Less crude was the Hartford friction damper invented in 1895. This had partially rotating clamped friction disks. A later version had hydraulic action. Such methods helped. That specifically needed was to dampen downward movement more strongly than upward movement.
Coil springs and torsion bars made this essential. The solution, de Carbon’s telescopic hydraulic dampers, are used to this day.
Beam axle – or independent
The suspension needed for travel trailers is totally different from that for passenger cars. Travel trailers pivot about the tow ball. They readily absorb even major bumps by rocking. Long travel suspension is not required. It has long since ceased to be on all but off-road vehicles.
Nor do travel trailers benefit from independent suspension. It is used either unthinkingly – or for marketing reasons. Beam axle suspension has many advantages. For example, it provides a stable platform at all times. The wheels remain at right angles to the road at all time.
Leaf springs do not necessarily have to be used. Other forms of spring exist. A major issue, however, is a lack of well-engineered leaf spring systems for travel trailers. Long, parabolic leaf springs are just fine. If self-building use those from the rear for a Hilux.
Travel trailer suspension – little need for compromise
Human physiology passenger car suspension. That required for optimal road holding is too harsh for comfort. Humans, on the other hand, do not travel in travel trailers. There is thus no need to compromise. But travel trailer makers pointlessly ape the type of car suspension used in American cars of the mid-1930s. Passenger car suspension has since had less, but more controlled vertical travel.
Travel trailer suspension needs to be engineered to suit travel trailer needs!
(The effect on humans etc is covered in depth in my Travel trailer & Tow Vehicle Dynamics.)
All this was thoroughly known by the mid-1930s. Despite that, most travel trailer makers ignore it. Or not aware of it. Some products defy basic laws of physics. One example is friction sway damping: makers seem unaware that frictional forces remain constant but the forces they are expected to absorb increase with the square of the rig’s speed.
Travel trailer suspension – further information
I cover suspension in detail in Why Caravans Roll Over – and how to prevent it, and The Travel trailer & Motorhome Book. Camper trailer suspension, likewise in the Camper Trailer Book. My other books are Caravan & Motorhome Electrics, Solar That Really Works (for cabins and RVs). Solar Success is for homes and properties. See also Wheels Falling off Trailers.
This topic often arises on RVers forums. If you find this interesting please consider posting this Link in on related threads.
How much solar capacity do I need?
How much solar capacity do I need
This article answers how much solar capacity do I need. It’s valid anywhere in the world that has enough sun. It can save you a lot of money.
The map below shows the amount you typically have available in Australia. Generally, solar is readily feasible where the daily amount exceeds 3.5. It is still feasible below that but needs a lot more solar capacity. The map shows the amount of sunlight in kilowatt/hours per day per square metre. This refers to any unshaded horizontal surface.
The solar industry, however, in its non-technical publications refers to one kilowatt/hour per day per square metre as 1 Peak Sun Hour. This is usually abbreviated to 1 PSH. The concept is akin to measuring rainfall in a rain gauge.
Solar irradiation in Australia. The units are kilowatt/hours per day per square metre. They are more commonly referred to as Peak Sun Hours.
How much solar capacity do I need – solar module alignment
Ideally, solar modules face due north (in the southern hemisphere) and due south (in the northern hemisphere). You do not need to take this too seriously. If you are more than 20 or so degrees out, adding about 10% more solar capacity (per every extra 10 degrees will compensate).
In terms of tilt, having the solar modules at your latitude angle results in the maximum yearly average. If you need more input in summer than winter, tilt them closer to horizontal. If you need more in winter than summer, tilt them more steeply.
Assessing current energy use
Your next stage is to assess how much electricity you need per day (and also of any rare peaks loads). You can simply look at your electricity bill and see. Then consider what you can do to reduce the draw.
Almost any existing home has 30 or more so-called wall warts. These are the little black boxes that enable you to switch appliances remotely. Many made prior to 2014 (and all cheap ones still) draw 3-6 watts even when the related appliance is switched off. That may not seem much. If, however, you 30 of them (some homes have more) that’s at least 90 to 180 watts, twenty-four hours a day (i.e. 2.16 to 4.32 kilowatt/hours a day. Worse, are items like 230 volt doorbells. One, personally experienced, drew a constant 40 watts, almost 350 kilowatt/hours a year. Yet activated a few times a week for a few seconds each time. Many a TV left on ‘standby’ all day draws far more a day than whilst being watched.
Items to replace – lighting
Replace all incandescent globes by LEDs. These provide better light at less than 25% of the same watts. LEDs last for many years: you recover far more their initially high cost over time. Be aware that ‘wattage’ no longer indicates light produced. Wattage is only a measure of the energy they draw. LEDs vary widely in this respect. Some are far more efficient than others. Their light output is shown in ‘lumens’. Their efficiency is thus lumens per watt. Because of this, LEDs that are cheaper to buy are likely to use far more long-term energy.
Items to replace – appliances
Recently made high-quality refrigerators draw far less energy. Replacing any made prior to about 2014 will save you money, in terms of how much solar capacity you need.
Air-conditioners likewise vary considerably in the amount of energy they draw. Assess their efficiency by looking for, or asking for, their CoP (Coefficient of Performance). This is the ratio of energy draw and work done. The higher the CoP the better. By and large units from 1.5 – 2.5 kW have the highest CoP. They cost more initially, but you will save over time.
Lighting for travel trailers – it makes every sense to install LEDs
by Collyn Rivers
Lighting for Travel trailers
Lighting for travel trailers has changed. Now, by far the most practical and least energy drawing are LEDs (light emitting diodes). This article shows why.
The best LED lighting for travel trailers now provides ten to twenty times as much light for the same energy as incandescent lighting. And ten times that of halogen lighting. An LED’s high efficiency is partly due to its light concentrated as a cone. Some light, however, is reflected from light coloured surfaces. If the need is to light a large space, compact fluorescents do so for similar energy use, and lower price.
LEDs work efficiently in travel trailers as for reading and cooking areas. They are also fine for outdoor lighting, and are good night lights. They draw so little energy there less risk of depleting an RVs battery.
Types of lighting for travel trailers – and their outputs
Low wattage (3-5 watt) LEDs fit the MR 11 thin dual-pin bases. Those from 5-10 or so watts fit the MR 16 dual-pin bases (used for 35 and 50-watt halogen globes). The MR 11 LED globe has pins 4.0 mm apart. It has a maximum of 35 mm diameter. The MR 16 has pins 5.3 mm apart. It has a maximum
diameter of 51 mm.
This typical five-watt MR 16 base LED produces light in a 60-degree cone – ideal for reading etc.
The MR 11 and MR 16 are fine for travel trailer and motorhomes. Their tiny pins do not, however, grip sufficiently over rough tracks etc. The latter requires MR 16 light fittings that secure the globes securely in place.
The GU10 style LEDs have thicker two-diameter pins. They inserted with a push and twist action. These are made in larger wattages. Many are supplied with tiny power converters. These enable the LEDs to run from 230 volts.
The GU10 based LEDs have pins that hold the globes firmly in place.
LEDs ease cabling issues
A major benefit of LEDs is that many travel trailers and motorhomes have 12-volt wiring that’s far too thin. This caused lights to flicker or dim when fridges cycle on/off. LEDs draw so little energy the original wiring is ample. They are also less sensitive to voltage drop.
LED strips are useful for lighting dark cupboards etc. They provide ample light yet draw next to no power.
Whilst an LED’s power rating is in watts, this gives only a rough indication of the light produced. The reason is (a) LED efficiency varies a lot from brand to brand but is substantially price related. A really good (e.g. Cree) 5 watt LED may produce several times as much light as a 5 watt eBay special. The best indication is the output in lumens (total light emitted). The more lumens per watt, the greater the efficiency. A top-quality 10 watt LED will produce as much light as a 100-watt incandescent.
The cone of light
There is a further complication. Most LEDs produce light in a cone. This may be from 15 degrees to about 140 degrees. There is none (but reflected) light outside that cone. Because of this, an LED of say 250 lumens may be just fine for a reading lamp. It is suitable where a broad spread is required. Lighting shops have working examples.
A typical RV needs four or five good quality 5-7 watt LEDs. Only a few will be needed at any one time.
LED globes are made in varying shades of white. They vary from the warm white of incandescent globes, to a hospital’s harsh white. For those seeking a ‘warmish’ light use LEDs that have a ‘colour temperature’ of 3100 degrees K (Kelvin) or at most, 4000 degrees K. Lighting store staff understand what this means.
Some people report excellent ultra-cheap LEDS from eBay. While cheap these LEDs vary hugely in quality and reliability. We have over 80 LEDs in our three-story home. All are top quality products and all but two have (2020) lasted over ten years.
Further information
LED lighting in camper trailers, travel trailers and motorhomes is covered in depth in the Caravan & Motorhome Book. It is also covered in the Camper Trailer Book, and Caravan & Motorhome Electrics. The latter covers every aspect of the design and installation of electrics and solar in camper trailers, travel trailers and motorhomes. Even auto electricians use it as a text and reference book. Solar That Really Works! covers every aspect of using solar in camper trailers, travel trailers and motorhomes, Solar Success is for home and property systems. For information about the author please Click on Bio.
This topic often comes up on forums. If you feel this article may assist others please consider posting this Link on the relevant thread.
RV supply cables – choices of current capacity and length
by Collyn Rivers
RV Supply Cables
This article shows the sizes and lengths of electric supply cables for RVs legally required in Australia and New Zealand.
RV supply cables – the basic requirements
Prior to 2008, some restrictions on RV supply cables ensured they were acceptable for other usages then under revision. Without those restrictions, supply cables would have been legal (and safe) for some uses, but not others. The revised requirements thus removed that risk. Furthermore, they resulted in a greater choice of approved lengths.
The new RV supply cables requirements are set out in Table 5.1 of AS/NZS 3001:2008 (as Amended in 2012). These requirements are still valid (July 2020).
The most relevant part is set out below. The lengths and sizes shown relate to typical supply cables for all RV and general use. There are, however, restrictions if used for loads such as large electric motors etc.
| Cable rating | Conductor area | Length |
|---|---|---|
| 10 amp | 1.0 mm² | 25 m |
| 10 amp | 2.5 mm² | 60 m |
| 10 amp | 4.0 mm² | 100 m |
| 15/16 amp | 1.5 mm² | 25 m |
| 15/16 amp | 2.5 mm² | 40 m |
| 15/16 amp | 4.0 mm² | 65 m |
RV supply cables (and general use). This is Table 5.1 of AS/NZS 3001:2008 as Amended in 2012. Extract reproduction by courtesy of Standards Australia.
Thou shalt not join cables together
There is an overall purpose behind specifying lengths and conductor sizes of supply cables. It is to ensure circuit breakers operate within that vital 0.4 seconds. To save a human’s life against electrocution, that short time is critical. Co-joining cables slow down the circuit breaker’s operation. That’s why joining supply cables end-to-end is so dangerous. It is also seriously illegal.
Supply cables must thus be one of the approved types and of one unbroken length.
10-15 amp adaptors
The restriction on co-joining cables applies also to 15-10 amp adaptor leads. These (illegally) enable 15 amps to be drawn through cable too thin to do so. Here again, doing so slows tripping of the associated circuit breaker. It may not trip in time to save a life. The Ampfibian 10-15 amp adaptor (described below) is legal. It restricts current flow from a 15 amp source, to 10 amps.
Never use a double adaptor to enable another travel trailer to share the socket outlet. This has always been dangerous. It is now illegal. If someone plugs your cable into a double adaptor, attempt removal amicably. If that fails, insist the park manager removes it for you.
The above requirements are not hard. Your supply cable must comply with the standard. You must use only one cable to connect your vehicle to the supply. If it is too short, obtain a longer one, or move the travel trailer closer. The only otherwise alternative is to forgo using that site’s power.
None of the above is negotiable. The requirements are clear and legally mandatory. Personal and forum ‘opinion’ is irrelevant.
How protective devices work
Supply cable rules take into account so-called Residual Current Device (RCD) and circuit breaker protection. An RCD compares the current flowing in both active and neutral leads. If imbalanced it is likely to be via a human to earth. The RCD should detect this and cut the current flow accordingly.
Circuit breakers monitor for excess current flow. They cut the current if an excess is detected. They primarily protect supply cables and appliances. Their effect is similar to fuses – but are more reliable.
10/15 amp issues
Early travel trailers used appliances that drew more current than now. That required travel trailer parks to have 15 amp socket outlets. You may, however, need to use a travel trailer where there are only 10 amp outlets. A 15 amp plug will not fit. It has a larger earth pin. Some people file down that pin to fit. Or make an illegal 10-15 amp cable. There cannot however be a weak link in a chain of safety. That includes not pulling 15 amps through plugs, cables and connectors designed to carry 10 amps. It’s like a 15-tonne winch with a 10-tonne cable.
You can, however, legally use a 10 amp supply cable for travel trailers if all related bits are also changed to 10 amps. That includes the inlet socket, RCDs and circuit breakers. Doing so thus prevents over 10 amps being drawn. Clipsal now has a 10 amp socket inlet that directly replaces the 15 amp unit.
The Amp-fibian
The Amp-fibian is a legal alternative. It is a short cable with a 10 amp inlet plug. It also has an inbuilt 10 amp circuit breaker and RCD. Plus a 15 amp outlet socket. It restricts supply to 10 amps but as most electrical appliances now draw less energy this not likely to be a problem.
The Amp-fibian 15-10 amp adaptor. A standard 15 amp supply cable is plugged into the receptacle (left) that is then sealed by a waterproof cover.
If seeking to power an RV at home, you can use that adaptor – or have a licensed electrician install a 15 amp power outlet socket.
The RV supply cables requirements apply now also to their general use.)
RV Supply cables – tagging
Occupational Health, Safety and Welfare Regulations include provisions for protecting staff. These include regularly inspecting and testing electrical equipment and supply cable. This latter activity is known as ‘tagging’. It generally enforced by travel trailer parks and RV rally organisers.
That it is needed was typically shown by a travel trailer club meeting in 2014. There, of 212 supply cables tested, 84 (40%) failed to pass. Five had broken earth wires within the plug or socket. Twenty-four had neutral and active conductors incorrectly connected – a total give-away of having illegally made one’s own cable. (The standard re-testing is AS/NZS 3760).
[caravan park] owners and managers, and rally organisers, are responsible for employee safety. There is also a general duty of care for those staying or visiting.
None of the above legally requires users’ cables to be tagged. Some travel trailer parks, however, enforce it. There is currently no legal requirement for them to do so. That may, however, be conditional for insurance cover. A travel trailer park can, however, enforce this as a condition of entry.
For cable taggers – check local Yellow Pages (or Google).
Outdated standards
Long-retired electricians may not be aware that fundamental safety approaches have totally changed. This, particularly, is true of earthing. Source documents are: AS/NZS 3000:2018, and the RV-related AS/NZS 3001.2008 (Amended in 2012).
Legal Disclosure
The above is sourced from Standards Australia’s documents (noted above)) I have an extensive practical and theoretical background in high voltage electrical equipment and systems. I am not, however, a qualified electrical engineer, nor a licensed electrician.
Further information
Further details about supply cables for travel trailers etc, is in Caravan & Motorhome Electrics, Caravan & Motorhome Book, and the Camper Trailer Book. My books on solar are Solar That Really Works (for cabins and RVs) and Solar Success (for home and property systems).
Solar input available for travel trailers – know what’s available and increase it too
by Collyn Rivers
Solar Input Available for Travel trailers
Knowing the solar input available for travel trailers is vital, especially up north. This article shows how to know that available and increase it too.
Knowing the solar input available for travel trailers etc. is like measuring rainfall. It uses Peak Sun Hours instead of inches or millimetres. Imagine an open drum that ‘collects and concentrates’ sunlight (rather than rain). When ‘full’, that drum contains one Peak Sun Hour (1 PSH). It is likely to fill in one hour in Alice Springs around noon on most days. In much of Australia’s south, filling one or two ‘drums’ during mid-winter takes most of the day.
The minimum likely is about 2.5 PSH/day for all areas except Australia’s south in midwinter. There, it’s too low to be effective.
Solar modules on a motorhome. Pic: courtesy Solar Energy Products
Solar input available for travel trailers – Peak Sun Hours
The PSH concept has a scientific background. The term ‘Peak Sun Hour’, however, was thought up by the solar industry. It is commonly but not technically recognised. One PSH is a solar irradiance (received sunlight) that averages 1000 watts/metre² on a horizontal surface for one hour. In reality, haze etc. results in a more probable 800 watts/metre².
In practice, even the best commercial solar modules are only about 20% efficient. Most are 14-18%, furthermore, there are heat and other losses. Solar input available is about 70-120 watts/metre² of surface area.
The daily solar input is thus 70-120 watt-hours times the daily Peak Sun Hours for each metre² of solar module area. It’s about 70% of that usually claimed.
Away from the tropics, about two-thirds of that input is during the two to three hours each side of noon. Depending on the season, solar input varies from 2 PSH (down south in winter) to 7-8 PSH in central and southern areas in summer.
Northern Australia has less variation. It’s about 5.5 PSH in winter and 6.5 in PSH summer. This is due largely to a high humidity layer. This absorbs some of the otherwise input. This often fools RVers – who assumed the opposite.
Based on NASA derived original data, this map shows the most probable (averaged) mid-summer solar output (in PSH) in Australia. This map is copyright rvbooks.com.au
Solar input available for travel trailers – Peak Sun Hours worldwide
Meteorological offices have solar input maps. The data, however, is in scientific units. My books Solar That Really Works, and Solar Success includes two maps that cover Australia. One is for mid-summer, the other for mid-winter. The maps are based on a ten-year running average (from NASA data). They are updated regularly. That for summer is shown above. There are daily variations. The totals provide only a general guide.
Solar input available for travel trailers -optimising solar output
The further north or south, the lower the sun tracks east to west. To optimise solar input, solar modules should face true north in the southern hemisphere. They should face true south for the northern. If located horizontally they’ll capture much of the day’s sun for much of the year. You can optimise input by adjusting portable solar modules every hour or two.
Solar modules do not need exact alignment. Most input is from 9 am to 3 pm when alignment is less critical. Furthermore, the sun’s effect is far from a ‘shaft of light’. It’s often diffused. Accurate alignment consequently makes little difference.
This is confirmed by the Australian Solar Radiation Data Book. That, for Adelaide during January, shows the difference between the 10º optimum and horizontal is only 0.16%. Even 20º error makes only 4% difference.
Across much of Australia, variations of plus/minus 20º, in north-facing or tilt cause under 5% difference. Where space allows, compensate by increasing (now very cheap) solar capacity.
Amorphous solar modules are less efficient, but only marginally heat affected. They are flexible, thus handy for curved roofs. They can even be glued on. If doing so, glue them on an aluminium sheet attached to the roof. Doing so eases possible repairs.
Solar input available for travel trailers – Multiple Power Point Tracking (MPPT)
MPPT solar regulators are often claimed to increase solar output. They cannot do that as such. What they can do is recover input otherwise lost. They ‘juggle volts and amps’ to optimise watts.
The common claim of ‘ by up to 30%’ is valid. That rarely revealed, however, is that increase is for an hour or two early and late in the day. Input then is tiny. An extra 30% (of very little) is barely worth having.
A more general approach
Until a few years ago, solar capacity was relatively expensive. It is now so cheap that, unless you need a minimal system for lighting only, have as much solar capacity as feasible. This will ensure batteries fully charge even overcast days. It will also provide adequate input in various areas and/or seasons.
Another good guide to existing RV systems solar input is this. Unless your batteries are fully charged by midday most year round there will be insufficient input up north excepting during mid-winter.
As solar capacity is now so cheap, it’s well worth having excess. The associated solar regulator precludes overcharging. What does not work is to increase battery capacity alone. Doing that’s like opening further bank accounts for the same money deposited. All it does is to increase storage losses!
Furthermore, battery charging/discharging loss is typically 20%. Increasing capacity unnecessarily is counter-productive. The more costly LiFePO4 batteries, however, are better in that respect. Their loss is about 5%.
Solar in tropical areas
As noted above, many RV owners assume that tropical solar input is greater year around. This is not so. The input during a tropical winter is typically 5-5.5 PSH/day, and 6.0-6.5 PSH/day in summer. There are also be fridge issues: in particular that not only is it hotter all day – it stays hot all night too. Fridge energy usage is usually 40% higher.
See also Article: Living with solar
Generator Backup
Given adequate solar capacity, an RV electrical system should run from solar or 95% or so of the time. There can, however, be atypical periods of overcast days. Smoke from major bushfires will reduce input to almost zero.
A need for generator back-up primarily relates to your desire for frozen food. If you replace that by vacuum-packed food, you can do without a generator. If you do need one, use it only to charge the battery/s via a high-quality charger from the generator’s 230 volts output. Never from the 12 dc outlet: that outlet is intended for running 12-volt devices directly. Its output (even if marked ‘battery charger’) is an unregulated 13.6 volts or so. That is far too low for effective charging.
Further information
This topic is not possible to fully cover in article form. If you find this one of value, there’s a huge amount more in my books.
Every aspect of solar is covered in depth in Solar That Really Works (for cabins and RVs). Solar Success covers homes and properties. My other books are Caravan & Motorhome Book, Caravan & Motorhome Electrics, and the Camper Trailer Book.
Fast battery charging from generators – cheap, effective and relatively simply
by Collyn Rivers
Fast Battery Charging from Generators
Fast battery charging from generators is cheap, effective and relatively simple. Few people, however, know how to do it. In many a campground, generators plug away for hours on end in vain attempts to fully charge their batteries. This article by RV Books’ Collyn Rivers explains how to get it right first and every time.
Most 120 and 230-volt generators also have a DC 12 volt and (typically) 8 amp output. Pic: Honda.
Almost all portable generators have a nominal 12-volt output. This outlet is primarily intended for powering 12-volt appliances directly (i.e. with no need for a battery). It typically supplies up to 8.0 amps. The ’12-volt’ output is typically 13.65 volts on light loads. Such output will partially charge a deeply discharged battery at 5-8 amps. Once the battery is 40%-50% charged, the current drops to an amp or so. Even if that outlet is marked ‘battery charger’ it may take a day or more to reach 60%-70%. It should eventually reach full charge, but may take a week or more to do so.
The simple solution
A cheap way of achieving fast battery charging from generators is via a basic 20 to 30 amp (230 volts) chain-store battery charger. You connect this to the generator’s 230 volts ac outlet. This will recharge a 100 amp hour battery from deeply discharged to about 80% within about six hours. A more costly multi-stage (dc-dc) 20 amp charger may reach 100% in even less time. Do not attempt to charge lithium batteries via a cheap charger. While normally rugged, (as with AGM batteries) they can be damaged or wrecked by over-voltage charging.
For a fuller explanation see dc-dc charging on this website.
Switch-mode technology issues
A known problem with fast battery charging from generators relates to some early so-called ‘switch-mode’ chargers and inverter/chargers. Some work well from grid power but not well (or even not all) from most 230-volt generators. The problem is not necessarily related to either unit’s quality or price: it is that a switch-mode power supply converts power by using electronic switching devices that rapidly turn on and off. Much like an engine’s flywheel, storage components (such as inductors or capacitors) supply power when the switching device is in non-generating brief states.
Switch-mode power supplies are highly efficient. They are widely used in computers and other sensitive equipment requiring a stable and efficient power supply. Switch-mode devices, however, require ‘clean’ electricity. That from basic petrol generators (the ultra-cheap eBay specials), however, is ‘dirty’.
Such generators speed up during each power stroke. They slow again on each compression stroke. The generator flywheel’s resistance to changing only partially dampens such rapid changes (they lack the size and mass to do so sufficiently). The consequent rapid speed changes cause voltage spikes on the electric output. Sensing ‘dirty’ electricity may cause a switch-mode charger’s protective circuits to limit output, or even switch itself off.
An owner faced with this (not uncommon) issue has a further problem. While the cause is the generator, each vendor may claim their product works fine (albeit not together). Each vendor tends to blame the other’s product. To avoid this, always buy both from the same vendor insisting they must work with each other.
This issue primarily affects low-priced petrol generators. It does not happen with inverter-generators such as the Honda/Yamaha type products.
In Australia, Power Protection Systems (supplier of Mastervolt etc) has a simple modification. It cleans up dirty input and tricks inverter-chargers into accepting any remaining ‘noise.’ It was designed specifically for Onan’s 3600 petrol generators and Dakar chargers, but is claimed to work with other generators.
Fast battery charging from generators – the power factor
A further issue called ‘power factor’ causes alternating-current (i.e. grid power) chargers and inverter chargers to charge at lower rates than had been expected. Power factor causes the alternating current to peak at a different time than the voltage. It’s rather like rowers sculling out of synchronisation. The same action and energy input has less effect. Power factor is expressed as between 0 and 1.0. The higher the better.
Adverse power factor is like two scullers (Ampy and Volty) rowing out of synchronisation. They do the same work as if they were together, but the boat will not go as fast. Pic: ‘Concentration’ – copyrightdreamstime.com
Most battery chargers have a power factor between 0.65 and 0.7. This necessitates using a generator that is correspondingly larger. Worse, most such chargers are only 70% efficient. A 12 volt, 30 amp (360 watts) such charger may thus need a 1000 watt generator to run it.
Switch mode chargers originally had poor power factor, but many now are 0.85-0.9 (i.e. 85%-90% efficient). Providing you avoid the cheap ‘specials’ this is largely a historical problem.
A charger that has really poor power factor can prevent an otherwise adequate-sized generator developing full power. A quick and dirty fix, that often works, is to run a 100-watt incandescent globe or soldering iron at the same time. It is not efficient but that resistive load tricks the generator into working as intended. An electrician can install power factor correcting capacitors to fix the problem, but the cost of doing so may be similar to buying a higher quality (that will power factor correction already built-in).
Further information
This article will hopefully help speeding battery charging from generators and other battery-charging problems. Many similar issues bedevil electrical, battery and solar systems in camper trailers, travel trailers, campervans and motorhomes.
That needed to fix them (and particularly avoiding problems in the first place) is in Caravan & Motorhome Electrics. It is also in the associated (now 4th edition) Solar That Really Works (for cabins and RVs) and/or Solar Success (for home and property systems). These books are now in eBook and paperback versions. Many auto-electricians use them as working guides. The Caravan & Motorhome Book covers every aspect of RV usage.
Generators for Home and Property Systems
Generators for Home and Property Systems
A backup generator is close to essential for home and property stand-alone solar. You can choose to down without but doing so may triple the cost of that system.
Generators for home and property systems are often needed as it is rarely feasible to size such a system for a 100% reliable solar supply. It is rare to have no input, but there will be days when solar input alone cannot cope.
Having solar and battery capacity for 95% of the time is readily feasible but extending that to 98% may triple the cost! That 95%, however, still leaves about 18 days a year where solar will not cope. Having a generator also provides emotional comfort.
Generators for Home and Property Systems
The most-used approach is a back-up petrol or diesel generator, but LP gas versions are also available. You need one big enough to run a few essential items directly – but primarily for battery charging. You use the generator’s 110 or 230 volts to drive a suitably scaled battery charger.
For homes and small properties, the larger Honda/Yamaha petrol-powered inverter generators used in up-market RVs are adequate for occasional use. For use to routinely charge batteries, the smaller diesel-power generators last far longer. Where noise is an issue with generators for home and property systems, Onan (Cummins) has a range of quiet units. These include generators that run on LP gas.
A few properties have a large diesel like the 25 kW Cummins Triton unit (below) scaled for massive (but rare) loads. Often essential for the larger outback properties areas but cheaper to hire a big mobile unit for a day or two for those with convenient city access.
Generators for Home and Property Systems – how to find out more
Full details of suitable petrol, diesel and LP gas generators are in our book Solar Success. This, as well as our other books: Solar That Really Works! (for boats, cabins and RVs), and Caravan & Motorhome Electrics for all aspects of the topic are now available in directly-downloadable digital form from our Bookshop. Print versions are available via all bookshops in Australia and many in New Zealand – and via email (right now) from booktopia.com.au.
Quietening travel trailer water pumps – easy and cheap to do
by Collyn Rivers
Travel Trailer Water Pumps
Quietening travel trailer water pumps is simple to do at no or trivial cost. This article from RV Books’ Collyn Rivers shows how.
Most travel trailers and motorhomes use 12-volt pumps that have a rotating cam. This cam drives a flexible diaphragm up and down, typically feeding three separate chambers. These chambers draw water as the diaphragm moves downward and close as it moves upward. This action forces water outwards through further valves. Each chamber operates at about 60 times a second. Noise is created by various parts of the action.
Quietening travel trailer water pumps – how and where to start
The first step in quietening travel trailer water pumps is to ensure the pump has a truly rigid mounting. Knock on the existing or proposed base. If it sounds like a drum it’s going to worsen pump noise. Ideally have a truly rigid base, but if not place a small piece of carpet between the pump and its base.
The pump is normally attached via screws and small rubber mountings. Use the thinnest possible hold-down bolts that will adequately hold the pump (Shurflo recommend high-tensile 2.0 mm bolts) and tighten only just sufficiently to marginally compress the rubber mountings. Do not overtighten.
Flexible piping essential
Noise is also transmitted through the flexible hose connecting the pump to the various outlets. A surprisingly effective way of quietening travel trailer water pumps is to reduce this transmitted noise. This is readily done by having a full loop of truly flexible hose (never use rigid copper) between the pump outlet and the rest of the system. This loop should be allowed to hang as loosely as feasible – ideally in free space. Unless able to move freely a lot of noise will still be transmitted.
Avoid right angle elbow fittings. They cause turbulent water flow and back-pressure. Both generate noise. Use smooth curves instead. Another cause of the noise is the vibration of the piping and any fitting where the hose passes through a wall. Use soft plastic foam as an insulator. Plumbing can also vibrate against walls and drawers etc
Once installed, bleed all air from the system as any trapped air causes the hose to rattle.
Start off with one already quiet
A good solution is to start with a pump that is already very quiet – such as the Shurflo WhisperKing shown below – mounted as described above.
The Shurflo WhisperKing works as described above, but is a lot quieter than most such pumps. Pic: Shurflo
Another approach is to use one of the quiet (post-2010) constant flow pumps. These circulate unused water around an internal loop in the pump body. They are much quieter but draw up to twice the current of previous models. This not a major problem in an RV, but can be in (for example) an irrigation system that supplies low pressure to drip feeds over for long periods of time. Another more recent innovation is the variable speed pump. This seems likely to become increasingly popular.
Further information
This issue, and also a solution that provides totally silent operation nearly all the time, is described, in Caravan & Motorhome Electrics, Solar that Really Works!, and Solar Success. If you liked this article you will like my books. My other books are the Caravan & Motorhome Book and the Camper Trailer Book. All are written in the same plain English down to earth manner. They provide solutions that work.
Lightning risk in RVs – how to reduce that risk
by Collyn Rivers
Lightning Risk in RVs
Lightning frightens, but lightning risk in RVs is very low. That risk however is far from random. Here’s how to reduce it yet further.
About 80% of those struck were using a land-line telephone. This risk is falling fast as people switch to risk-free mobiles. Golfers however are particularly at risk, especially if swinging a club. Also at risk is anyone using an umbrella during a storm, or walking on a beach. It’s not that hard to reduce the odds!
Some areas of Australia are especially prone to severe thunderstorms. These include the Blue Mountains, the Dandenong Ranges, the Kimberley, and the north of Australia (generally during the monsoon season). The lightning risk in RVs in these areas is very much higher than in most other areas. It is primarily for those living or travelling in such areas that this article is intended.
Lightning strike over Geelong (Victoria) in March 2012. Pic: (by Rod Howard) courtesy Geelong Advertiser.
How lightning strikes
At all times, the earth’s surface carries a typically negative charge. The upper atmosphere carries a positive charge. As a storm develops, the voltage difference builds up to many hundreds of millions of volts. Once the voltage between ground and upper atmosphere exceeds a certain level, the air ionises (i.e. electrons become freer to move). This eases the passage of a lightning strike much as straightening or surfacing a road initially eases traffic flow.
So-called ‘step leaders’ reach down toward earth and (like early pioneers, the one that gets there first tends to set the route for that which follows). On earth, objects respond by sending out positive voltage streamers. When such a streamer meets a step leader, a conductive link is formed. The resultant current flow generates so much heat that the surrounding air literally explodes – resulting in thunder claps.
Lightning risk in RVs – seek shelter if outside
The most dangerous place to be in a thunderstorm is out in the open but there is usually a fair amount of notice. A good rule is to seek shelter once a thunderstorm is within 10 kilometres. That’s about 30 seconds between seeing the lightning flash and hearing the thunderclap. Stay sheltered for at least 30 minutes after the last lightning is seen.
If you are caught out, avoid becoming a positive voltage streamer – such as a golfer in mid-swing. Do not use an umbrella. You are actually safer if soaking wet as any current is more likely to pass through the wet clothing.
If the risk seems very high, crouch down with feet together and with your head held low. Never shelter under a tree. If you have to stand, keep your feet as close together as possible. This is because a nearby strike causes voltage differences of thousands of volts per metre in the nearby ground. Having a few hundred volts difference between one foot and the other leaves you very dead. Absolutely do not lie down.
Almost any form of building is safer than being outside but keep away from walls, metal plumbing etc. Do not use the loo (water is conductive). The lightning risk in metal-bodied travel trailers, motorhomes and coaches is exceptionally low. A metal structure (even of metallic mesh) provides a so-called ‘Faraday cage’ within which all current flows through the external metal to earth. Within such an RV you may not even be aware of a strike.
If the storm is at least 10 km away, lower the TV antenna (disconnect it at least). Physically disconnect all external power leads. Do not, however, do either if a storm is closer.
‘Cone of protection’ is a myth
Ignore all campfire and forum Internet mythology about the ‘cone of protection’ provided by tall trees and buildings. These attract lightning strikes. Such strikes cause a voltage gradient that spreads out on the ground beneath and near the sides of a tree or building. This can kill at up to 30 metres or more from that strike’s centre. Essentially nowhere outside a building or vehicle is safe whilst lightning is around.
Whilst a vehicle’s tyres might appear to insulate the vehicle from earth, all rubber tyres now contain carbon. They are deliberately semi-conductive to limit static charge build-up. At lightning’s voltages, tyres become good conductors. In storm conditions, however, do not exit an RV holding the door handle whilst touching the ground. It’s best not to go outside anyway.
All large external metal structures attached to a travel trailer or motorhome (e.g. air conditioners) should be bonded to the chassis using at least 6 AWG cable.
Lightning rods
These work by dissipating ‘electrical charge’ built up where the voltage difference does not become high enough to attract a ‘step leader’. They work best if they have a point at the top. That point concentrates and assists charge dissipation. A lightning rod is well worth having in lightning-prone areas – such as the Kimberley.
Lightning risk in RVs that have fibreglass or composite bodied vehicles is reduced by having a conventional lightning conductor with a (sharp) spike. This should be well above the roof and earthed to the vehicle chassis via starter motor cable that runs externally. If you do this never use soldered joints as the massive current flow will melt them instantly. Instead have an auto-electrician crimp them for you.
Lightning seeks the straightest path. To reduce lightning risk in RVs keep any such earthing cable as straight as possible and routed well away from where people may be.
Lightning risk in RVs – further information
For those seriously interested in lightning risk in RVs, the Standards reference is AS/NZS 1768:2007.
The topic of electrics and travel trailers generally is covered in depth in my book Caravan & Motorhome Electrics. That of solar for cabins, camper trailers, travel trailers and motorhomes is in Solar That Really Works!. That for larger home and property systems is in Solar Success. My other books are the Caravan & Motorhome Book, and the Camper Trailer Book. For information about the author please Click on Bio.
Grid connect solar modules for RVs – here’s how you can use them
by Collyn Rivers
Grid Connect Solar Modules
Using grid connect solar modules for RVs is readily done but needs an MPPT regulator. This article by Collyn Rivers explains how and why it is done.
Grid connect solar modules are often sold very cheaply. Most, however, produce optimum power at voltages that cannot be handled by the 12-24 volt solar regulators used in most RVs. Using grid connect solar modules for RVs is however readily done by using an MPPT (Multiple Power Point Tracking) solar regulator. An MPPT regulator accepts a much wider voltage range. Grid connect solar modules for RVs can also be used in stand-alone solar systems. This article by Collyn Rivers (RV Books) explains how and why.
Grid connect modules are made in a huge range of voltages and sizes. Those of around 300-350 watts tend to be the best value for money. Most output about 50 volts at 60-7 amps.
Juggling volts and amps
An MPPT solar regulator ‘juggles’ incoming volts and amps to produce whatever needed to charge your solar system’s batteries deeply, speedily and safely. For RVs such as camper trailers, travel trailers and motorhomes this is usually a (nominal) 12 or 24 volts.
Care is needed when buying an MPPT solar regulator when using grid connect solar modules for RVs. Some accept any input voltage from as low as 9.0 volts to often well over 100 volts. But some work only from 9-36 or so volts. Others have an upper limit of about 50 volts. This will be shown in the maker’s literature.
This 400 watts Morningstar MPPT solar regulator is ideal for smaller systems. It will accept input from solar panels up to a nominal 36 volts. (The maker emphasises its suitability for use with grid-connect solar modules for RVs.) Pic: Morningstar.
MPPT regulators do not need prior setting for incoming solar voltage. They do, however, need setting for the type and voltage of the battery/s used (e.g. lead-acid, AGM, gel cell etc), and usually for the capacity (amp hours). This is usually easy to do. If in doubt ask the vendor (or most girls or boys from 9 upward).
The Australian-designed (now US-made) Outback Power MPPT units will accept up to 110 volts or so at up to 80 amps – ideal for larger systems on motorhomes converted coaches – and home stand-alone systems. Pic: Outback Power.
Can I legally install grid connect solar modules for RVs myself?
In Australia, it is legal for non-electricians to install grid connect solar panels for RVs etc, as long as the solar array’s nominal voltage does not exceed about 65 volts. The peak off-load voltage must be under 120 volts dc. This typically limits solar module output to a (nominal) 72 volts.
You are unlikely to experience other than a tingle up to 24 volts. Care is still needed, particularly if working on the RV’s roof. Anything above 50 volts or so can give quite a shock. Unless experienced in electrical work have someone who is to assist you. If the modules produce, or are series-connected, to produce above 120 volts dc, you must use a licensed electrician.
Be aware that many (probably most) ultra-cheap solar regulators are claimed to be MPPT – when they are not. Stay only with known brands.
Further information
Full details of all this, plus a great deal more is included in my books: Caravan & Motorhome Electrics, Solar That Really Works! and (for bigger systems) Solar Success. See also related articles (under Power/Solar) on this website. My other books are the Camper Trailer Book and the all-new Caravan & Motorhome Book. For information about the author please Click on Bio.
Motorhome and trailer tyres
by Collyn Rivers
Motorhome and trailer tyres
Motorhome and trailer tyres take a far greater beating than those in general use – an industry report noted that such tyres are subject to major abuse greater than any other form of use. In particular, stated the report, travel trailer and motorhome tyres are often grossly under-inflated and overloaded.
The best general usage motorhome and trailer tyres for use in Australia are LT (Light Truck) tyres. Be aware though that their heavier construction does not enable them to carry a heavier load. It enables them to run at or near their maximum load at all times.
The maximum load that a tyre can legally carry is a function of heat build-up. It is also speed-related. That heat build-up is greater with light truck tyres. Their thicker side-walls and tread support generate more heat as they flex. To minimise this they must be inflated to pressures higher than for the equivalent passenger tyres.
This tyre has either been grossly overloaded and/or underinflated. Pic: original source unknown.
Current trends
The current trend is toward larger rim diameters, lower tyre side-walls and greater widths. More extreme examples resemble ultra-wide bicycle tyres. There are various reasons for this. Increased rim diameter enables better brake cooling and/or creates space for larger diameter brakes. The low, wide profile provides more responsive handling and more precise steering. It also reduces side-wall flexing and hence heat build-up. As less energy is lost in heat and rolling drag reduced, less fuel is used. With these tyres, having the right tyre pressure is particularly important.
Travel trailer and motorhome tyres pressure also profoundly affects on-road behaviour, in particular the ratio of tyre pressures front/rear. This is too complex a topic to discuss here – but it is covered in-depth in my article Travel trailer and Tow Vehicle Dynamics.
Except for extreme off-road going (rock-hopping) tyres with normal on-road tread patterns are fine for dirt road use. They are actually better in the sand. I once drove a 1940 QLR seven tonne Bedford twice the length and breadth of Africa. This included two full Sahara crossings. The truck had standard 1100 by 20 London bus tyres. If interested see Last Drive Across Africa.
Pressures to use
Those travel trailer and motorhome tyres that are wide and of low profile run at pressures in excess of 750 kPa (over 100 psi). This is needed to maintain their profile and prevent their on-road footprint collapsing. This is (2016) still a problem in that many service stations compressors pump only to 530 kPa (77 psi). If travelling outside city areas buy a tyre compressor capable of doing this reliably with big tyres. If caught out, limit your speed to 65 km/h until you are able to have the tyre correctly inflated. Any major pressure difference seriously prejudices handling (especially in emergency situations).
Wide tyres improve on-road handling but are less effective in sand etc than high profile tyres. Tyre flotation is mainly a function of the length (not width) of the tread’s ‘footprint’. High profile tyres (such as 750 x 16s) extend that footprint length at low pressures. Low profile, wide tyres swell out sideways at low pressures but at far too high a level to be of any value in sand etc. Worse, they form a V shape that causes them to dig in.
Tyre footprints usefully lengthen as pressure is reduced. Pic: Peter Wright.
For dirt road use, lower travel trailer and motorhome tyres pressure by 20%-25%. Keep speed below 80 km/h to limit destructive heat build-up. Lower pressure also reduces the risk of a blow out when you hit a rock. The tyre ‘folds around’ it. (At full pressure tyres resist distortion. Rocks may punch through them on impact).
Makers’ recommend tyre pressures now allow for heat build increase in pressure of 4%-5% so they should only be adjusted when cold. They are thus slightly under-inflated but attain their correct pressure after 10-15 minutes driving. Do not lower them.
Knowing on-road weight
Correct travel trailer and motorhome tyre pressures are related to on-road weight. Travel trailer and motorhome weight varies with loading. The only reliable way to know that weight is (when fully laden and with water tanks full) to take the vehicle to a Certified Weighbridge and check individual axle loadings. If you advise the weighbridge operator beforehand that you do not need a Certified weight it usually costs less. Some do it free of charge. You must also add the weight of yourself and passenger/s plus all you intend to carry. Then ask the tyre maker’s technical department what pressure to use. (Do not attempt to guess the weight of personal effects, books, food etc – people who do tend to underestimate by at least 100 kg (220 lb), and often twice that).
Further information
This issue is also covered in depth in the 2nd edition of the author’s The Camper Trailer Book. It is also covered in depth in my Caravan & Motorhome Book.
If you liked this article Caravan & Motorhome Electrics, you are likely to also enjoy my books. Apart from the above, there are Solar That Really Works (for cabins and RVs) and Solar Success (for home and property systems). All are written from personal experience and in plain down to earth English. The author is an ex motor industry research engineer who switched careers mid-life to become a technical writer/editor and publisher.
Make travel trailer fridges work as claimed – here’s how to do it
by Collyn Rivers
Travel Trailer Fridges
To make travel trailer fridges work as claimed, and draw less energy, is cheap, simple and easy. Many can be transformed. This article shows how.
Pic: Original source unknown
Fridges do not generate ‘cold’. They pump heat from where it is not wanted to somewhere it does not matter.
Big fridges use more energy than small ones, but not in proportion to their size. Doubling fridge volume will increase energy draw about one and a half times, not twice. Where feasible, use one large fridge – not two smaller ones.
Some cold air is lost when a fridge’s front door is opened. Top-opening fridges lose marginally less. The heat seals of door-opening fridges must be perfect, if they are not, energy usage soars. If they are over three years old, replace them.
Energy consumption
Any fridge’s energy draw relates directly to ambient temperature. All use about 5% more for every 1° C above 25° C. Set temperatures are the same. Fridges need to be +4° C, freezers -18° C (or settle for -14° to save energy).
Cool food before placing it in the fridge. Keep bought frozen goods cold in a heat-insulating bag, and put in the fridge as soon as possible. Defrost anything frozen in the fridge section. Let warm beer first cool overnight. If you keep the fridge full less cold air falls out when opened, so leave gaps for air to move, but fill empty spaces with bottled water.
Most fridges control temperature by cycling on and off. Energy draw relates to the ratio of on times to off times. A fridge that draws more energy but is on less often, or for shorter times, may use less energy per day. Many makers now produce fridges that run constantly: they vary the speed to maintain temperature. For any type of fridge only daily energy draw has any meaning.
Make travel trailer fridges work as claimed – from solar
It is totally feasible to make electrical travel trailer fridges work as claimed primarily from solar. A typical 40-110 litre chest and door opening electric fridge draws 0.7-1.0 amp-hours/day per litre of its volume. Larger ones draw slightly less per litre. This requires 150 to 200 watts of solar, and 100 to 150 amp hours battery capacity per 100 litres of fridge volume in temperate areas (up to 30º C). Above 30º C, solar capacity needs increasing by 5% for each 1º C. Alternator charging assists if driving a few hours each day. See dc-dc-charging/
Three-way fridges work well on gas, from the alternator whilst driving and 110/230 volts when available but their energy draw (12-30 amps at 12 volts) is far too high for solar. See below re ‘Climate Class’.
Unrealistic expectations
Fridges must be competently installed. Few are. Improve them by following that shown below. (Owners comparing fridges unknowingly discuss competent or otherwise installation).
No travel trailer fridge will cool a carton of room temperature beer in an hour or two! Buy beer cold and put it straight in the fridge. Fishers (particularly) grossly underestimate energy needed to freeze their catch. Power draws continuously, doubling or tripling consumption, yet the catch will not freeze quickly. Doing so requires a generator-powered chest freezer.
Correctly installed and sensibly used RV fridges will work as specified, but don’t get carried away by vendor’s claims. Believe the claims in technical data, not those in brochures.
Gas and three-way fridges must suit the climate in which they are used. If not they are not likely to work as you may expect.
Three-way fridges and climate class
Three-way fridges maintain cooling over tightly defined ambient temperatures. These are four (CEN standard) Climate Classes. The ‘SN’, and ‘N’ (Sub Normal, and Normal) units work up to 32° C; ‘ST’, (Sub Tropical) up to 36° C. ‘T’-rated (Tropical) up to 43° C. (T- and ST rated fridges do not work that well below 14°-18° C.) Only ‘Climate Class T’ cool satisfactorily in north and north-west Australia (or tropical areas generally).
Three-way fridges are available in Australia from Chescold, Dometic and Indel. They have an unfair reputation for poor cooling due either to buying one of the wrong Climate Class and/or poor installation. Three-way fridges meet their claims but must be installed as shown above to do so.
Make travel trailer fridges work as claimed – in tropical areas
When making a fridge work as claimed, it is common (but wrongly) to assume there’s more solar input in tropical areas. There is not. Solar input in the tropics in mid-summer is 20% to 30% less than many expect. High humidity causes haze and some solar energy is lost because of this.
It is also hot all day and often all night, so fridges draw up to 50% more energy, meanwhile, solar modules lose energy through heat loss.
To cope in tropical conditions, your solar system must bring batteries to float voltage in temperate areas by noon on most days
All this is thoroughly covered in my books Solar that Really Works, Solar Success and Caravan & Motorhome Electrics.
Installation
Few RV fridges are correctly installed, including many done ‘professionally’. Making travel trailer fridges work as claimed is usually possible: sometimes even better than claimed – and often at little or no cost. It is usually easy to do but in extreme cases, it may be necessary to totally re-install.
Here is a far from extreme example: it is of a $550,000 motorhome with a 450-litre fridge totally enclosed and unventilated, plus a 300-litre freezer. Both are in unventilated lockers with black fronts exposed to the sun. Neither cools below about 5 degrees C. Both connect to the battery via cable barely able to run LEDs. The RV maker refuses to accept responsibility – he blames the fridge maker! Fixing required a major rebuild of the kitchen area at a cost of over $10,000!
Heat must escape
Whilst seemingly obvious, a fridge must not be in direct sunlight:
One character, who has his outside in Broome’s full tropical sun, complains: “my b..y mongrel Electrolux won’t keep my %#@^& beer cold.” He’d listen to nobody (including me) explaining why – despite going through a 9 kg (20 lb) LP gas cylinder a week as a result.
The heat from a fridge must be able to exit the travel trailer – and not re-enter. To do this they need a cool air entry at its base level, and a hot air exit (ideally at roof level). Most need baffles to direct cold air so that it can only flow through or over the cooling fins. Baffles can be made from aluminium, plywood or even cardboard. They must be within a centimetre or two of the cooling fins. Channel rising warm air so none is trapped.
The cool air vent can be at the side or through the floor (but not above or behind an engine’s exhaust outlet). Cool air must enter below the lowest cooling fin and exit well above the highest fin.
The lower inlet is a problem off-road as dust is sucked in. Here, compromise is needed. One way is to have the vent closed off while on dirt roads (but cooling will suffer as a result).
Rising warm air is ideally vented to and through the roof: if not feasible, have a side vent well above the highest cooling fin.
Fridge level is important. Some three-way fridges tolerate 6° tilt, others only 3°, but electric fridges are less sensitive.
The vital requirements
![Make [cara] fridges work as claimed - here's how to do it - electric vehicle batteries,book on batteries,electric car batteries,lithium ion batteries for electric cars,electric car battery technology,how long do electric car batteries last,electric vehicle battery life](https://solbsau.centrails.com/wp-content/uploads/2023/12/Fridge_installCombined.jpg "Make [cara] fridges work as claimed - here's how to do it 139")
Upper Left: – the baffles are too short. They need to be just below the cooling fins. Rising hot air is trapped in the dead air spaces. If not fixable (bottom centre and right), an extractor fan driven by a 5-watt solar module enhances airflow. Upper right: – the upper air vent is far too low – hot air is trapped in the fins above it, to prevent that, baffles are needed. Below: How to install fridges correctly. Baffles truly help, yet rarely used. Rising hot air is channelled to the outside. Drawing is copyright: rvbooks.com.au
A small extractor fan often assists. Some have an integrated solar panel – this works well as cooling is most needed when sunny. Fans used in large desktop computers are cheap. They run directly from a 5-10 watt solar module or the RV’s 12-volt system. Ideally use fans to extract warm air rather than pumping in cool air – but the difference is minor.
Solar-powered extractor fans (Google for suppliers)
Electrical problems with 12-volt fridges
Most 12 volt fridges have grossly inadequate cabling – many only 25% of that required. Check by seeing if the fridge cools better on 230 volts (where relevant). Cable issues are worsened by faulty fuse holders: and particularly cigarette lighter plugs and associated too small wiring. Scrap such plugs and wire the fridge to the battery by the shortest route.
To check if the cable is too small, with the fridge running, measure the voltage directly across the battery, then directly across the fridge. To ensure it keeps running, do this with the fridge door open. Many travel trailer fridges have close to 1.0-volt drop. Accept no more than 0.15 – 0.2-volt drop.
Using adequate cable makes an extraordinary difference to make travel trailer fridges work as claimed. For an electric fridge to battery distance of fewer than four metres, use 4 mm² cable (AWG/B&S 11). Over four metres use 6 mm² cable (AWG/B&S 9). If over four metres, move the battery closer.
Do NOT use the auto cable sold by auto parts and hardware stores without first reading about it below – or in more detail in Caravan & Motorhome Electrics.
Do also see DC-DC Charging – this shows how ensure the travel trailer battery and fridge receive their full required voltage from the vehicle alternator. This can totally transform a travel trailer or camper trailer fridge.
Auto cable problems
Appliance makers specify cable by its cross-section in mm². Auto cable makers (in effect) specify it by the size hole you can just push it through. They rate it by its overall diameter including insulation!
Auto cable sold as 4 mm is typically 1.8 mm², but maybe only 1.25 mm². Many travel trailer electric fridge makers specify 4 mm². But countless fridges are connected by totally inadequate 1.8 mm² auto cable (less than half the minimum specified). No fridges wired that way work remotely as they should and usually can. Direct comparison with other wire gauges is impossible with auto cable as conductor size varies from maker to maker. One exception is that 6 mm auto cable (typically 4.59 mm² – or 10 AWG) can be substituted for 4.0 mm² cable.
Cable current rating trap
Cable ‘ratings’ (e.g. ‘50-amp’ etc) indicate only the current that cable carries before it melts! They tell nothing about voltage drop (as that is also a function of cable length). It’s useless asking most vendors about this because few know it’s even an issue – let alone why. For travel trailers, locate the battery close as possible to the fridge. If alternator charged, install a dc-dc alternator charger close to that fridge’s battery.
Never use cable lighter than advised above. If you do the fridge cannot work correctly
An exact way of establishing the best cable size is shown in my books, Solar that Really Works, Solar Success and Caravan & Motorhome Electrics.
Problems with three-way fridges
Routine maintenance is required. Check the flame colour: it should be blue. If yellow (or the fridge works well on 12 volts but not on gas), the baffle inside the flue is likely coated with soot. Soot etc also drops down and affects the burner.
Wearing safety glasses and old clothing, use a powerful air compressor to clean that baffle. Do likewise around the burner. Be aware this is a filthy job. You may prefer a fridge repairer to do it – and have them check the LP gas pressure at the same time.
Whilst uncommon, an LP gas fridge may suddenly stop working. This is usually caused by a ‘vapour lock’ due to the travel trailer being excessively out of level. You can usually fix this by turning the fridge off, and make sure the travel trailer is level (within 3 degrees) – then turn the fridge back on after a few hours.
A cause of cooling issues with gas fridges in imported RVs (or imported gas fridges) is if they are made for LP gas in a different country. If so, the jets can the wrong size. If so, seek expert advice.
Use three-way fridges as their makers intend. Run them on 12 volts only whilst driving or an hour or so from the battery because they draw too much energy to run from solar.
For travel trailers, use heavy cabling – ideally 10 to 13.5 mm² – from the alternator to the travel trailer battery. Consider installing a dc-dc alternator charger close to that travel trailer battery. Use at least 6 mm² cables from that battery to the fridge.
Make travel trailer fridges work as claimed – in cars and 4WDs
Making travel trailer fridges work as claimed in cars and 4WDs is more of a problem. Keep them out of direct sunlight, and leave air space around the grill’s vent areas. It is fine to pack stuff close to or touching them – except for the types shown below (these must have a 50 mm air gap each side as the heat dissipates from their sides).
You can improve all types of fridges (some dramatically) by running a 6 mm² (8 AWG) cable directly from the battery to that fridge (a maximum of four metres away). Use 6 AWG if the distance exceeds four metres.
A few boat and RV fridges, such as this Australian designed and made Autofridge, dissipate heat from their side-walls. These fridges must have an air gap of 50 mm each side. Pic: Autofridge Australia.
Fridge issues generally
Do not over-pack RV fridges as space is needed to allow cool air to circulate.
Door seals leak after a few years. To check, insert a strong strip of this paper (e.g. a banknote) between the door and the seal (at various places around the door) and see if it grips. If not cool air escapes, so replace the seals every three to five years – you can buy replacements from stores such as Clarke Rubber.
Fridges with external cooling fins benefit by adding extra heat insulation. Some fridges, however, such as the Intel and Autofridge (pic above), dissipate heat from their side-walls. If possible have a cool air feed to the base of their sides. They must have an air gap (of 50 mm or so) at either side and their top.
Make travel trailer fridges work as claimed – summary
It is totally possible to make almost all RV fridges work as claimed (or even better) via the work described above.
Except for the very cheapest fridges, dismiss claims of inherent deficiencies. If a fridge is appropriate for its proposed use, problems are almost always due to faulty installation. For domestic fridges, and fridges in cabins, virtually all of the above is relevant.
Further reading
A great deal more on how to make fridges work as claimed is in my book Caravan & Motorhome Electrics. It even shows how to build your own fridge that leaves commercial units for dead in cooling and economy. That book includes a lot of information about running them from solar. So does Solar that Really Works!
If the fridge is large and in a large home or on a property consider also Solar Success.
There is detailed information about every aspect of travel trailers and motorhomes in the Caravan & Motorhome Book. For camper trailers see the now second edition Camper Trailer Book.
If you find this article useful you will find my books even more so. Each has updates at typically yearly intervals. RV Books accepts no advertising. It does not accept payment for editorial. It covers the cost of all articles solely from the sale of the associated books.
Weight Distribution Hitch limits cornering
by Collyn Rivers
WDH Cornering Issues
This article explains why a weight distribution hitch limits cornering. A weight distribution hitch is often referred to as a WDH.
A travel trailer‘s essential need to be front-heavy imposes a down-force (weight) on the rear of the tow vehicle. It is like pushing down the handles of a loaded wheelbarrow. It reduces the down-force (weight) on the tow vehicle’s front tyres.
If the laden travel trailer weighs the same (or less) than the laden tow vehicle the weight transfer effect is minor. In Australia, however, travel trailers increasingly (and undesirably) outweigh the tow vehicle.
A Weight Distribution Hitch (WDH) assists to restore that otherwise ‘lost’ weight. In doing so, however, a WDH inherently reduces the rigs’ cornering ability.
Furthermore, a WDH reduces the speed at which a rig may become terminally unstable if subjected (for example) to a strong side wind gust from a passing truck. The tighter the WDH is adjusted, the lower the speed at which instability may occur.
That rig is likely to be safer with that WDH, but you need to accept its limitations and downsides – and how to adjust that WDH and drive accordingly.
Adequate tow ball weight is essential
Tow ball weight is essential. It enables a towed travel trailer to stay in a straight line unless steered by the tow vehicle. The tow ball weight needed relates to the travel trailer‘s length and loading. The longer the travel trailer, the greater the tow ball weight required.
For correctly laden travel trailers (i.e. weight mainly centralised), about 10% of the travel trailer‘s laden weight should keep the rig stable up to 100 km/h. If the tow ball weight is less than 10%, the rig may become unstable at lower speeds, particularly in emergency swerves at speed.
That tow ball weight is imposed on a hitch that is (on average) 1.2-1.5 metres behind the tow vehicle’s rear axle. With locally-made travel trailers, the imposed weight maybe 250-350 kg (550-775 lb). Increasingly, however, many new tow vehicles, however, are unable to cope with that weight. It may over-stress the chassis (or rear body structure) and/or the rear suspension and tyres. This particularly affects post-2015 vehicles as, in that year; most manufacturers of vehicles used for towing reduced the chassis thickness (from 3.5 mm to 3.00 mm).
How a Weight Distribution Hitch Works
Tow ball weight pushes down the rear of the tow vehicle – thereby increasing the weight on its rear tyres. A WDH, in effect, is a semi-flexible springy beam that levers back up the rear of the tow vehicle and levers down its front. In doing so, however, it reduces the imposed load on the tow vehicles rear tyres and partially restored it on its front tyres. Reducing the load on the tow vehicle’s rear tyres reduces their ‘cornering ability’. This is why a WDH limits cornering.
The main failing (often overlooked) is that a WDH only addresses travel trailer down-force. It does not (and cannot) reduce the side forces imposed on the rear of the tow vehicle when the travel trailer yaws (sways). If, as not uncommonly, fitting the WDH extends the hitch rear overhang, it makes those yaw forces even worse.
The effect of yaw forces on the tow vehicle
The yaw forces described above are imposed on the tow vehicle’s rear tyres. The WDH, however, has reduced the weight carried by those tow vehicle’s tyres. That reduced weight reduces those tyres ability to resist the yaw forces.
If/when the rig starts yawing, those (yaw) side forces literally steer the tow vehicle by its rear tyres, and e.g. those side forces increase their slip angle. In emergency situations, this can cause the tow vehicle to oversteer. If that happens, and within a few seconds, sway forces escalate to jack-knifing. No matter how skilled this sequence cannot be driver-corrected.
The faster the rig is being driven the more serious the situation. This is because yaw forces increase with the square of the rig’s speed. In other words – the forces are four times greater at 100 km/h than at 50 km/h.
The speed at which the above happens is related to tow ball weight. The lower that weight the lower the ‘safe’ speed. This is why travel trailers with front-located water tanks were mostly recalled – as ‘safe tow ball weight relied on those tanks being full at all times.
WDH adjustment and front axle load restoration
For stability at speed etc all road vehicles have a margin of so-called minor understeer. If a vehicle is cornered too fast, understeer automatically causes that vehicle to take up a slightly wider radius – thus reducing the cornering forces. Understeer’s opposite (‘oversteer’) causes a vehicle to tighten its turning radius yet more and more – until that vehicle spins.
An inherent effect of a WDH is to reduce the tow vehicle’s margin of understeer. It is essential to adjust the WDH to keep that reduction within acceptable limits.
WDH adjustment
The Society of Automobile Engineers’ Standard J2807 requires that a WDH must never be used to level the rig. Doing so results in transferring excess weight to the tow vehicle’s front tyres, and reducing the weight on its rear tyres. This effect is often misunderstood (even by some WDH vendors). It reduces the essential margin of understeer.
The recommended so-called ‘50% Front Axle Load Restoration’ results in the front wheel arch of the tow vehicle being about 50 mm higher when the laden travel trailer is hitched up. The travel trailer‘s nose may be down slightly. This just fine – do not attempt to level it: those days have long gone.
How to adjust the WDH to do this is shown in https://solbsau.centrails.com/page/caravan-tow ball-weight/
See also https://solbsau.centrails.com/tow-vehicle-caravan-weight-ratio-explained/. It explains how to load a travel trailer safely.
Never use a WDH with a travel trailer, that when laden, weighs the same or less than whatever tows it. There is absolutely no benefit, and doing so may introduce undesirable effects.
All the above and a great deal more is explained (in plain English) in our (digital) book ‘Why Caravans Roll Over – and how to prevent it’. It is available in various formats – and costs far less than fixing a rolled travel trailer.
Weight distribution hitches and Land Rovers
Whilst repeatedly being queried on a local Travel trailer‘s forum, Land Rover’s position regarding the use of a WDH on its products is totally clear.
In Land Rover’s own wording. ‘Do not exceed the Gross Vehicle Weight (GVW), maximum rear axle weight, maximum trailer weight, or the trailer’s nose weight. Doing so can cause accelerated wear and damage to the vehicle, and adversely affect the vehicle’s stability and braking. Serious injury or death can also result from a possible loss of control leading to an accident.
The use of weight distribution hitches is not recommended. Using weight distribution hitches can potentially cause serious damage to the vehicle.’
http://www.ownerinfo.landrover.com/document/LS/2016/T22693/18742_en_GBR/proc/G1800997
In essence that which Land Rover is saying is that if you tow a sensible weight travel trailer you do not need a WDH. If you do use one, however, the action of that hitch adversely interacts with the Land Rover’s automatic levelling system.
Comments
RV Books cannot respond to any direct questions relating to why a weight distribution hitch limits cornering. Various other articles on this website address other issues relating to tow vehicle and travel trailer stability.
RV Books updates this article when deemed necessary.
Dc-dc charging – how to speed alternator charging
by Collyn Rivers
Dc-Dc Charging
Dc-dc charging charges boat, cabins, camper trailer, travel trailer and motorhome batteries faster and deeper. Collyn Rivers explains how and why.
Pic: original source unknown.
A rechargeable battery is charged by applying a voltage higher than the battery already has. The higher that voltage difference the quicker such a battery charges. As a battery charges its voltage rises. If that charge voltage is constant, however, the difference between that and the charging battery falls.
Alternators charged at a more or less constant 14.2-14.4 volts until 2000. A few still do. Batteries so-charged rarely exceed 80%. As a result, many in travel trailers never exceed 65%. Moreover, they take hours for even that.
For some years after, many alternators were temperature controlled. They charged at 14.1-14.2 volts when cold. This reduced to about 13.2 volts once warm. Both types can be made to work well for battery charging via dc-dc alternator charging described below.
Variable voltage alternator charging was introduced around 2013. These are controlled by the engine’s central computer unit. They vary the voltage from 15.4 volts to 12.3 volts. Some drop voltage to zero.
How starter batteries are charged
A vehicle’s starter motor is designed to work with 70%-80% charged batteries. The energy required to start cold engines is tiny. It’s less than 2% of battery capacity. This is typically replaced within two minutes. It’s cheap, rugged and simple. Fine generally for starter battery charging – but not for RV use.
Dc-dc charging
Dc-dc alternator charging overcomes these problems. Working fast, deeply, yet safely, it accepts whatever voltage available. Next, it converts it to that optimally required. It bulk charges at whatever current the battery accepts. Such units thus constantly increase charge voltage as battery voltage rises. This enables charging fully, deeply and rapidly.
Such technology, used for telephone exchange batteries for decades, was later adapted for vehicles. See Battery charging and battery chargers.
Dc-dc charging truly scores with batteries distanced from the alternator. Voltage drop prejudices charging, and fridge operation. Heavy cable is necessary. Locating the dc-dc unit close to the battery ensures adequate voltage. It also extends battery life and can transform three-way fridges.
Voltage sensing relays
These systems require a VSR (voltage sensing relay). The VSR senses starter battery voltage. It directs charge to that battery for two to three minutes after starting. It allows auxiliary battery charging once the starter battery exceeds 13.6 volts. The VSR isolates the starter battery if it drops below 12.6 volts. Some dc-dc chargers have VSR functionality inbuilt.
Regenerative braking
Many hybrid vehicles use regenerative braking. Their starter battery is normally 80% charged. Braking increases alternator voltage. This boosts battery charge to 100%. The battery then provides all electrical energy required. During this, alternator output is zero or too low for charging. This causes the VSR to open. That precludes auxiliary charging for minutes each time.
Regenerative braking necessitates dc-dc charging. It is often known as bc-dc. With this, the charger senses the starter battery voltage. I cover these units in Variable voltage alternator problems with travel trailers/ The article also shows how to know your alternator’s type.
Bc-dc units are made by companies including Redarc and Sterling Products. Some companies now produce all such products as bc-dc. Moreover, those for use with variable voltage alternators are of Low Voltage form (see above Link).
Installation is generally similar to that below. There is, however, no voltage sensing relay. A signal lead is taken from the ignition switch. Makers give full details.
Installing dc-dc charging
Dc-dc charging ensures a battery is alternator-charged safely, deeply and fast. Ensure this locating the charger close to the main energy load and battery. That load is typically a fridge or fridge freezer.
Dc-dc charging optimises charging but you still need adequate cable. Use 10 mm² (ideally 13.5 mm²) from source to charging unit. Makers explain this – but rarely stress its need.
Most such units ensure starter battery charge priority. Recharging generally takes only two to three minutes. If inbuilt protection is not provided (excepting for bc-dc units) a VSR must be used.
Some dc-dc charging units have an inbuilt solar regulator, and/or mains battery charger. The sketch below shows a typical installation.
Installation may vary from brand to brand and type to type. The unit shown will charge an auxiliary battery from a 12-volt alternator. Furthermore, it does so at up to 40 amps.
How to install a typical dc-dc or bcdc charger. The function safeguarding starter battery voltage is inbuilt. Pic: Redarc.
Programming dc-dc charging
Different battery types require different voltage/current settings. Dc-dc chargers have programs accordingly. No programming is needed for alternator voltage. The systems accept whatever that is.
Lithium (LiFePO4) batteries have different needs. Redarc consequently has units specifically for this purpose. It stresses they be used only with LiFePO4 batteries they recommend.
The specialised Redarc LFP series of dc-dc battery chargers for (specific) LiFePO4 batteries. Pic: courtesy of Redarc.
Issues with dc-dc charging
Basic dc-dc alternator charger does not work well (or at all) with variable voltage alternators. Moreover, doing so may damage the auxiliary battery/s. See above re bc-dc charging.
Initial charging of a deeply discharged battery is generally limited to a basic dc-dc charger’s capacity. Dc-dc chargers under 20 amps may take longer to attain half charge. Thereon, charging is hugely faster. The CTEK Smartpass dc-dc charger overcomes this. Moreover, it allows direct alternator charging until dc-dc charging takes over.
This is of less issue with 30-50 amp units. With these, charging limitations are mostly alternator output, and (for some batteries) the maximum they’ll absorb. This is a lesser issue with gel cells and AGMs. It is not an issue with LiFePO4s.
Pic: CTEK ‘Smartpass’ dc-dc charger. Pic: courtesy of CTEK.
Further information:
If you like this article you’ll truly benefit from my books. All are in down to earth English. Moreover, they are technically accurate. Furthermore, batteries and battery charging is covered in depth in Caravan & Motorhome Electrics.
Solar that Really Works! covers cabins and RVs. Solar for larger homes and properties is covered in Solar Success. The Camper Trailer Book and the Travel trailer & Motorhome Book cover innumerable issues in depth. Click for my Bio.
See also the many articles on this website. Moreover, click here for Article index.
If you like this article, do please add this Link to any related forum query. Moreover, doing so assists others as well as RV Books!
Battery charging and battery chargers – how to do it properly
by Collyn Rivers
Battery Charging
Battery charging and battery chargers are often misunderstood – causing batteries to die before their time. This article explains why and how to avoid it.
Batteries charge by applying a voltage that is higher than that existing. The greater the voltage difference, the faster and deeper it will charge. That voltage must, however, be tightly controlled. If too high, it damages or wrecks batteries.
Historically, vehicle alternators generated 14.2-14.4 volts. Cheap battery chargers still do.
As the battery charges, its voltage rises towards the charging voltage. The voltage difference between the battery and the charger thus constantly reduces. The charging rate falls accordingly.
Battery charging and battery chargers – like filling one tank from another that’s much bigger
Charging is like filling a small tank from a huge one (of similar height) via a hose between the bottom of each. The water level in the small tank slowly rises until levels equalise. As with ponds, alternators need not know the battery state of charge. The charging battery simply rises in voltage. As it does so, charging tapers off. Eventually, voltages are equal. Charging then ceases.
Many RV batteries charge this way. They take many hours to fully charge. Most never do. Given many days continuously, however, they may even overcharge.
Starter batteries
A starter motor draws surprisingly little energy. Following engine starting, the alternator replaces it within two to three minutes. Such charging is crude but cheap and simple. It works well enough for starter batteries, but less so for RV auxiliary batteries. These are limited to slow charging. Few reach full charge.
Constant current charging
Serious battery charging is done at constantly increasing voltage. This maintains a constant rate of charge current throughout 80-90% of the charging cycle. A final stage is usually done at a constant voltage. There are variations. All, however, work much as below. Conventional lead-acid, gel cell and AGM batteries are similarly charged.
Lithium-ion batteries, however, require a different regime. This is described later in this article.
Boost stage
The initial ‘Boost’ stage constantly increases charging voltage as the battery voltage rises. Its intent is to keep charging current at the battery’s safe maximum. For a lead-acid deep cycle battery that’s typically 20% of its amp/hour capacity. For large batteries, that limit may the battery charger’s ability to do so.
Boost typically continues until the battery voltage reaches about 14.4 volts. That battery is nevertheless not yet fully charged.
Absorption stage
Battery charging is an electro-chemical process. Like many such, it is slow. The charge, in effect, is held within the water/acid electrolyte. At this stage, however, the ‘charge’ is uneven. It is concentrated in and around the battery’s plates. Evenly distributing the charge requires ‘absorption’.
Absorption is typically at voltage ensuring charge current is about half that previously. It typically requires two or so hours.
Float stage
Following Absorption, charging current reduces such that it counterbalances battery internal losses. This stage is called Floating. It is 13.2-13.6 volts for AGMs and gel cells. Conventional lead-acid batteries require 13.6-13.8 volts.
As with the Absorption stage, charging revert to Boost if battery voltage drops. This may happen if there’s a heavy load.
Keep lead acid deep cycle batteries as fully charged as possible. Their life is otherwise shortened. If an RV is unused for more than a week or two – keep its batteries on Float charge.
AGM batteries, however, hold 50%-60% of their charge for a year or more. Whilst rugged, even minor long-term overcharging damages them. Unused AGMs need to be initially fully charged – then only after every 6-12 months. Do not leave them on ‘float charge’. It may ruin them.
Equalising
Some chargers have (usually optional) ‘Equalising’. This heavily overcharges the battery for an hour or two.
The original idea was to equalise cell voltage. Technology changes, however, render it unnecessary. Most battery makers now recommend against it. Never do it AGMs, nor gel cells. Nor, in my opinion, with any battery.
Different battery types require different voltage/current settings. All good quality battery chargers are programmable accordingly. Currently, only a few have programs for LiFePO4s. See ‘Lithium-ion battery charging’ below.
Caution when buying a battery charger
Always use a high quality multi-stage battery charger. Cheap ones sooner or later wreck costly batteries. A multi-stage charger brings a battery up to charge rapidly, deeply and safely. A 10 amp multi-stage charger will thus outperform almost all ’20 amp’ conventional chargers. And many a ’25 amp’ cheapie. Good chargers start at about $250.
Lithium-ion battery charging
A lithium-ion (LiFePO4) cell is nominally 3.2 volts. A 12-volt such battery thus has four such cells. Charging is typically at constant current. It requires 13.2-13.6 volts. This charges the battery to about 80%-90%. Many users settle for about 80%.
It is vital that each LiFePO4 cell maintains equal voltage. Ensuring this requires cell management. This also prevents current draw below a preset state of charge. These systems are available from LiFePO4 vendors. They may not, however, be included with the battery. It is essential one be used.
LiFePO4 state of charge
LiFePO4 state of charge is difficult to assess by measuring voltage. A 100% charged 12 volt LiFePO4 battery maybe 13.4 volts. In typical RV use, this drops to 13.1-12.9 volts at 90% or so charge. It’s then virtually constant until 10% remaining. It then drops rapidly.
Some battery charger makers include a final voltage charge. This brings a LiFePO4 close to 100%. Many users, however, claim this shortens battery life. This may well be so. Reliable evidence, however, is not readily available. See Lithium-ion batteries in travel trailers for an overview.
Solar Regulators
Good (plus $275) solar regulators have multi-stage charging. The better ones include MPPT (multiple power point tracking). This recovers 10%-15% of energy otherwise lost.
Further information
See also DC-DC charging – also Speeding Battery Charging from a Generator and also Lithium-ion Batteries in Travel trailers
If you liked this article you will like my books on RVs and solar. Batteries and battery charging are covered in depth in Caravan & Motorhome Electrics. Solar That Really Works! is for cabins and RVs. Solar Success relates to homes and properties. See also the Caravan & Motorhome Book and the Camper Trailer Book.
LP Gas risk in travel trailers – deaths & brain damage still occurs
by Collyn Rivers
LP Gas Risk in Travel trailers
A major LP gas risk in travel trailers is carbon monoxide build-up. Low levels cause brain damage and death at high levels. Here’s how to eliminate the dangers. Carbon monoxide builds up as a direct result of burning LP gas in any inadequately ventilated confined space. The risk in RVs is high enough to take seriously. Since 2009 about 12 people (in Australia alone) died in travel trailers due to the above. In the USA it typically exceeds 1000 people a year. Far more have suffered brain damage.
The earlier so-called coal gas produced by burning coal in the virtual absence of air resulted in 10% or so carbon monoxide. It was so potentially lethal that it was used with caution. LP gas, however, has a lower carbon monoxide content. It takes longer to kill. Nevertheless, ‘some 30% of people with severe carbon monoxide poisoning are likely to die as a result’. [1]
LP Gas risk in travel trailers – quantified
Inhaling even relatively small amounts of the LP gas can lead to hypoxic injury, neurological damage and even death’ [2]. Carbon monoxide exposure may lead to a significantly shorter life span due to heart damage [3]. Exposures at 100 ppm (part per million) can be dangerous to human health [4]. Carbon monoxide poisoning is the most common cause of injury and death due to poisoning worldwide. [5].
About 35 ppm (parts per million) of carbon monoxide causes headache and dizziness within six to eight hours. Some 200 ppm (about 0.02%) causes a slight headache within two to three hours. Plus loss of judgment. At 800 ppm (0.08%) there are dizziness, nausea, and convulsions within 45 min. There is insensibility within two hours, and death within three.
At 1600 ppm, and still only 0.16%, there is ‘headache, tachycardia, dizziness, and nausea within 20 min. Death occurs in less than two hours. Even at 6400 ppm (0.64%) death occurs inside 20 minutes. At a far from high 12,800 ppm (1.28%), you become unconscious after 2-3 breaths and will be dead in less than three minutes’. [6]. The natural atmospheric level is about 0.1 ppm. The exhaust from a warm car’s exhaust that lacks a catalytic converter is 7000 ppm. [7]
The main causes of LP gas risk in travel trailers
LPG and fossil fuels require a lot of air to burn safely. Doing so in an enclosed space increases LP gas risk in travel trailers. It decreases the oxygen content, thus increasing carbon dioxide concentration. The amount of air required varies with the nature of that gas. Appliances mostly used in boats and travel trailers etc. are intended to run from propane. If used, as some do (illegally plus dangerously) with Autogas, incomplete combustion may produce more carbon monoxide.
That Autogas may not be used for any purpose than its original intent is covered in various legislations. The main one is Clause 5.1.1 of AS/NZS 5601. This states that appliances must be designed, verified and certified to use only a specified gas. No domestic appliance is so certified.
It is also forbidden under 9A (1) of the Gas Safety Act 1997. This in effect recognises that Autogas has a composition other than LP gas.
Incomplete combustion is indicated by a yellow content in the flame. As 100% burning cannot be guaranteed, space heating in Australia, and many other countries, thus requires burning to be sealed from the space heated.
LP gas (in this case it is propane) should burn with a totally blue flame. Any trace of yellow indicates incomplete combustion – and the generation of carbon monoxide.
Direct oxygen deprivation
Increasing the LP gas risk in travel trailers is that our breathing contaminates the air. We take in about a half a cubic metre of air every hour. Of that, we convert about 4% of into carbon dioxide. The exhaled carbon dioxide level thus rises. The available oxygen level falls. The latter is normally 21% or so. It may, however, drop to 15% before symptoms (such as fatigue) set in. Oxygen deprivation through this alone has been tragically demonstrated. ‘Illegal’ migrants have been asphyxiated inside sealed trucks.
The risk of brain damage at lower levels of exposure, where ventilation is poor, is only too real. Those over 40 or so, children, and people with heart and respiratory problems, are likely to suffer from the effects. They do so sooner and more severely as may heavy smokers.
LP Gas risk in travel trailers – Australian government study
As a result of ongoing deaths, a formal (Australian) initiative made people (particularly travel trailer users) aware of the risks. It was called the ‘Gas Appliances (Carbon Monoxide) Safety Strategy’. I prepared the formal submission for the Caravan and Motorhome Club of Australia.
That submission included: ‘Our view is not so much that the existing regulations relating to LP gas installation in RVs necessarily need changing. It more that owners do not take the known risks sufficiently seriously. That is shown often, not only on (the then) cmCA’s forum. It happened (and still does), on other forums.
I noted that ‘the major risk identified (in our opinion) is that of LP gas appliances being used in an inappropriate manner. For example, LP gas ovens left on with the door open to provide heat. Iron plates and ceramic pots placed over LP gas rings for the same purpose’. I also alluded to ongoing illegal use of LP gas catalytic heaters ‘in poorly ventilated annexes and within the RV itself.’
The submission also noted: ‘A further issue is the often alleged lack of quantitative data on reported incidents of carbon monoxide poisoning in RVs. This has created concern because warnings of the dangers are frequently met by denial. The basis of that is typically ‘that no hard data is available.’ There is, however, ample such data.
LP gas risk in travel trailers – Australian government action
Rules regarding LP gas risk in travel trailers have since been tightened in the USA, Australia and New Zealand. The previous Australia-only Gas Standard has been replaced by the joint AS/NZS two-part Standard AS 5601.2013. That RV relevant is Part 2. (Gas Installations in travel trailers and boats for non-propulsive purposes). Legally ‘travel trailers’ now includes all RVs.
As with its predecessor, AS 5601:2013 states, ‘amongst appliances that shall not be installed in a travel trailer is a space heater, other than a room-sealed type.’ This rules out suggesting gas oven doors be left open to heat a travel trailer. And similar idiotically dangerous suggestions.
(AS/NZS standards define RVs as being/: ‘a structure that is or was designed or intended to move from one place to another, whether towed or transported, which is intended for human habitation . . . and includes a self-propelled recreational vehicle.’)
Item 6.9.4 of the new Code thus calls for a permanently legible warning. This must have a minimum character height of 4.0 mm. It must be affixed ‘in a conspicuous position on or adjacent to, the ‘[gas cooking]’ appliance and shall provide at least the following information:’
WARNING
Ensure ventilation when the cooker is in use.
Do not use for space heating.
Appliances defined
It is for very good reason that using LP gas for direct space heating in travel trailers is illegal throughout Australia. Further, any cooking appliance used for space heating by any form of burning gas is defined as a ‘gas appliance’.
It is still occasionally argued that a ceramic pot or whatever placed over a gas ring, or an oven door left open is ‘not an appliance’. This overlooks that devices are legally defined in terms of intent. Not necessarily content. A screwdriver may thus be defined as a device for dealing with screws. Or in dangerous areas at night, as an offensive weapon. The same reasoning extends to LP gas cylinders and cans of petrol. Either, carried onto a plane, is designated a bomb.
Safe heating
Germany’s Webasto and Eberspächer companies produce (very similar) diesel-powered space heaters and space plus hot water power heaters. The Eberspächer product is also sold under the name Dometic. There are also many look-alikes. Truma has an LP gas-powered equivalent.
All draw fresh air in from outside and exhaust to the outside. These are the only form of heating that can be recommended for cabins and RVs. They are fully covered in the Caravan & Motorhome Book and The Camper Trailer Book.
Ventilation openings
The minimum free area of the permanent ventilation that must be provided is defined in Section 7.3.1 of AS/NZS 5601:2 2013. This applies also to a pop-top travel trailer whether the top is up or down. This must be at least 4000 mm², or that value from the formula below (whichever is larger):
V = (610 X U) +( 650 x P)
V is the minimum free area (in square mm) where:
U is the input rating for all gas appliances, including the cooker, in MJ/h (as on the rating plate) P is the number of persons for whom the ‘compartment’ is designed.
The Standard stresses this is the minimum required. It should be exceeded where feasible. It also notes that mesh or screen reduces the ‘free area’. That must be allowed for. The openings must be at opposite ends or sides of travel trailers. But not, however, in the rear wall of a ‘motorised travel trailer’ (e.g. motorhome).
New Zealand
Until 2010, the then Gas Standard (AS 5601) related only to Australia. This was primarily because Australia’s LP gas is either propane or mostly propane with a small proportion of butane. That in New Zealand is propane and up to 50% butane.
Appliances built to burn one form of LP gas can be hazardous when used to burn another. The Gas Regulator’s view was that (as with using Autogas to replace LP gas) it poses an unacceptable safety risk to New Zealand and Australian consumers. This issue is now resolved. The reference is ‘Australian RV appliances increasingly being certified for use with Universal LPG Gas to accommodate the NZ market’. It was from the NZ Office of Energy Safety, 18/09/2012.
(This ‘Universal LP gas’ issue affects only Australian gas appliances made for the NZ market).
Proffered advice and ongoing denial
The ‘advice’, commonly found on website forums to the effect: ‘it is only dangerous if you do not stay awake’ etc shows an astonishing lack of understanding. Doing that oneself is dangerous enough. To advise others to do is seriously illegal.
Were someone to die as a result of following such advice, the consequent charge can even be manslaughter. Further, those inciting others to perform an illegal act, commit a criminal offence.
This came to a head in early 2012. Three men died from carbon monoxide poisoning in a travel trailer in Tasmania. Despite the Coroner’s report not then published, and media reports based on speculation, many forum posts denied that LP gas was the cause.
References (general)
References to local usage are in Australian Standard AS 5601:2013. This is now in two parts. Part 1 is for domestic applications, Part 2 is for travel trailers and boats. ‘Travel trailers‘ is used there as a generic term for any transportable structure.
These Standards are hugely costly but until recently could be obtained on loan by most public libraries
Further information
See also my Safe travel trailer and motorhome heating. Further information on gas installation is provided in the Caravan & Motorhome Book, and The Camper Trailer Book. My other books are Caravan & Motorhome Electrics, Solar That Really Works (for cabins and RVs). And Solar Success (for homes properties). For details of the author’s background please Click on Bio.
Almost all of the above article is applicable also to New Zealand.
AS/NZS 5601(2013) Parts 1 and 2, Published by the Standards Association of Australia.
AG 601 – 1995 Gas Installation Code, published by (the Australian) The Gas Installation Code Committee.
The Annual Report of the (SA) Technical Regulator 2005-2006 (p.7).
Office of Gas Safety (Vic) – Guide to Gas Installations in Travel trailers & Motorhomes.
Similar guides are available from all state gas regulatory bodies.
New Zealand (facts and data) – Permanent Exemption of LPG appliances from the Trans-Tasman Mutual Recognition Arrangements. (Regulation Impact Statement for Consultation – 2008.)
References – specific
I research topics routinely prior to writing anything technical – but rarely include such references in material intended for general reading. I include references (from refereed papers from major journals etc) here to stave off ‘that’s just your opinion’ responses.
1. Varon J, Marik PE, Fromm RE Jr, Gueler A (1999). “Carbon monoxide poisoning: a review for clinicians”. The Journal of Emergency Medicine 17 (1): 87–93.
2. McDowell R, Fowles J, Phillips D (November 2005). “Deaths from poisoning in New Zealand: 2001-2002” (Free full text). The New Zealand Medical Journal 118
3. Raub JA, Mathieu-Nolf M, Hampson NB, Thom SR (April 2000). “Carbon monoxide poisoning-a public health perspective”. Toxicology 145 (1): 1–14. Raub JA, Mathieu-Nolf M, Hampson NB, Thom SR (April 2000). “Carbon monoxide poisoning-a public health perspective”. Toxicology 145 (1): 1–14
4. Henry CR, Satran D, Lindgren B, Adkinson C, Nicholson CI, Henry TD (January 2006). “Myocardial Injury and Long-term Mortality Following Moderate to Severe Carbon Monoxide Poisoning”
5. Prockop LD, Chichkova RI (Nov 2007). “Carbon monoxide intoxication: an updated review”. Journal of the Neurological Sciences 262 (1-2): 122–130.
6. Thom SR (October 2002). “Hyperbaric-oxygen therapy for acute carbon monoxide poisoning”. The New England Journal of Medicine 347 (14): 1105–1106
7. Carbon Monoxide. Washington, D.C.: National Academy of Sciences. 1977. pp. 29. ISBN 0-309-02631-8.
8. Struttmann T, Scheerer A, Prince TS, Goldstein LA (Nov 1998). “Unintentional carbon monoxide poisoning from an unlikely source”. The Journal of the American Board of Family Practice 11 (6): 481–484.
9. “OSHA Fact Sheet: Carbon Monoxide”. United States National Institute for Occupational Safety and Health. http://www.osha.gov/OshDoc/data_General_Facts/carbonmonoxide-factsheet.pdf.
10. http://dspace.rubicon-foundation.org/xmlui/bitstream/handle/123456789/7964/DHM_V38N3_breathing_ gas.pdf?sequence=1.
RV Fuel cells – great idea, but cost is too high
by Collyn Rivers
RV Fuel Cells
RV fuel cells are non-polluting and ultra-quiet. Whilst initially promising their initial and running costs still excludes general RV use.
RV fuel cells have been touted as the ideal energy source since 2005. There have been 12 years of promotional claims. But so far, however, only a few products have surfaced. The arguably best one – Truma’s LP gas VeGa – however, sadly failed to sell.
Fuel cells are part generator/part battery. They use hydrogen and oxygen to generate electricity. As hydrogen is not widely buyable, fuel cells thus derive it from fossil fuel. Any such will (theoretically) do.
Right now, three fuel cells brands suitable for RV use are (more or less) available.
EFOY
The EFOY sells globally. Those marketed for RV use produce from 130-180 amp-hour/day. That is 1600-2200 watt-hours/day. They are about the size of a jerry can. Weight is 7-8 kg (15-18 lb). As with all fuel cells they can be run 24 hours a day. The EFOY uses methanol – about one litre per 1.1 kWh. This, however, is supplied in purpose-made 5.0 and 10-litre canisters. Fuel costs about $10/litre.
The EFOY methanol-powered fuel cell. Pic: Webasto.
Locally available (claimed high quality) methanol is available in 20-litre drums. It costs a fraction of the price. Ultra high-quality fuel is, however, claimed essential. Warranty, furthermore, is invalid unless EFOY’s fuel is used.
There are also industrial and military versions.
The RV units were initially around A$3500. Around, 2012, however, that escalated. To close to $10,000! A subsequent distribution change reduced prices, They are nevertheless still $6000 upward.
Truma VeGA (now defunct)
The VeGa was originally to be delivered in 2007. This became 2008, 2009, 2010. Then ‘early 2011’. Delays, as a result of corrosion issues, were finally overcome. Sales began in 2013. The resultant price (10,000 Euros) proved too high. The unit consequently ceased selling – in 2014.
The Truma VeGA unit – alas no more. Pic: Truma.
Hydromax
The Dutch-designed Hydromax 150 is much the size as the EFOY. It runs from two water-based solutions. One is a salt. The other is malic acid. (Malic is found, improbably in fruit such as apples!).
Hydromax fuel cell
When mixed, this produces hydrogen. The hydrogen molecules are then split by a catalytic converter. That creates electrons. The only waste is water and a little malic acid. The unit produces about 12.5 amps at 12 volts. (This product seems to be no longer available.)
WATT Imperium
As with the (defunct) Truma VeGA, the US designed WATT unit runs on LP gas. A 9 kg (20 lb) cylinder is claimed to generate about 3400 amp hours at 12 volts. This is about 40 kW/hrs. The output is about 14 hWh/day.
Diesel
Diesel-powered fuel cells are being produced in Scandinavia. They are, however, currently too costly for the RV market.
Fuel cells for RVs – installation
Installing the (above) fuel cells is mostly providing ventilated space. Their exhaust is claimed, specifically, to be virtually pollution-free. It is mainly pure water or water vapour.
Small fuel cells need a battery to supply loads exceeding their maximum output. High energy capacity, however, is not required. Energy stores more efficiently in the fuel these cells run from. Starter type batteries are thus fine. So too are LiFePO4s.
Fuel cells for RVs – an economic alternative?
Often-made comparisons with petrol generators are flawed. Such generators are only fuel-efficient whilst under 50%-80% load. That works fine if that amount of energy is for battery charging. On light loads, however, they gobble fuel. Emission regulations. also, may eventually preclude generators.
Fuel cell consumption is virtually proportional to load. Their ability to provide silent, non-polluting electricity is thus a major bonus. Unless money is no issue, they are thus best used to back-up solar etc. Not (yet) as a prime energy source.
Fuel cells for RVs – medium/long-term
The Truma VeGa was a hugely costly failure. It finally worked well. But it cost far too much to sell.
Fuel cell technology nevertheless may yet change the world’s energy economy. It could be from petroleum – to hydrogen-based. This nevertheless requires massive change. Benefits, however, are equal. Hydrogen can furthermore be produced from renewable resources. It can also be readily stored.
This, moreover, is not just conjecture. General Motors suggested a US-wide hydrogen infrastructure. Its aim? To place a hydrogen pump within 3 km of 70% of the US population. Plus every 40 km on most interstate roads. The (2003) cost estimate was US$10-15 billion. A major hydrogen pipe-line has now been built in the USA’s Gulf states.
How fuel cells work
How a typical fuel cell works. Pic: courtesy of Michegan Molecular Institute, USA.
As like conventional batteries, fuel cell technology typically combines many cells. Each produces a small amount of power. Individual cells contain a positive electrode (the cathode). Plus a negative electrode (the anode). The electrodes are separated by a solid or liquid electrolyte.
Hydrogen is fed to the anode. Oxygen (from the air) is fed to the cathode. The hydrogen splits into positively charged protons and negatively charged electrons via a platinum catalyst. The protons are able to flow to the cathode via an external circuit. This thus produces usable electrical energy. The re-united protons and electrons combine with oxygen at the cathode.
Further reading
The topic of fuel cells in RVs is covered in Solar That Really Works! (for cabins and RVs). For RV electrics, see Caravan & Motorhome Electrics. See also Caravan & Motorhome Book, and the Camper Trailer Book. Solar Success <a ” href=”https://solbsau.centrails.com/solar-success/”>is for homes and properties.
The cost of these books is furthermore repaid multiple times. For example – by getting the system right the first time. The author (Bio) has both engineering and writing/publishing backgrounds. The books are technically competent and in plain English.
Electrical converters in RVs – they’re unsuitable for free-camping
by Collyn Rivers
Electrical Converters in RVs
Electrical converters in RVs supply 12 volts from 230-volt power. They work well from 230 volts, but not for long-term camping. Here’s how to fix the problem.
Electrical converters in RVs supply 12 volts dc from 230 volts ac in Australia/NZ, and most of Europe. These converters are intended for RV rental users, private owners for casual use, and those spending most nights in travel trailer parks. Their purpose, says one maker, is to ‘provide a dc power system, with optional battery backup’. Another maker describes that backup as ’emergency power’.
The ‘battery backup’ has limited capacity. It is likewise intended for limited or occasional use. Where 230 volts is available, lights and appliances are powered directly from the converter. The battery is used only when 230 volts ac is not there.
Typical up-market converter. Pic: setek.com
Electrical converters in RVs – unsuitable for free-camping
Electrical converters in RVs work well and reliably for their intended usage. That usage does not extend to free camping for more than one night. Nor do vendors suggest otherwise.
If the RV has LEDs, and uses only appliances originally installed, it should cope with one overnight stay. But rarely two. The vehicle must be driven for some hours the following day. And/or recharged every second night. This is best done from a 230 volt supply via a high output mains battery charger.
Free camping usage however requires a system run from the RV’s alternator, solar or a generator-charged battery. It uses 230 volts only to recharge batteries fast.
Limited charging
Most electrical converters in RVs charge batteries slowly. They do so because their output is typically only 13.65 volts. This is far too low for quick, let alone deep, charging. This is usually made clear in makers’ literature. One advises a deeply discharged 120 Ah battery so charged may ‘take 10 hours to attain 80% charge’. Plus ‘a further 10 hours to fully charge.’
Another advises that charging that same size battery ‘requires up to 70 hours’. Overnight usage away from 230-volt power typically discharges such battery/s by 60%-70%. The inbuilt charging system precludes fully re-charging the following night (assuming 230-volt power). This, say, vendors, safeguards the battery from being overcharged. But no high-quality charging system overcharges batteries anyway.
The above is openly revealed in converter specifications. Only buyers with technical understanding are likely to understand the implications.
RV vendors may explain how to use the system. They rarely advise, however, that usage does not include extended free-camping. The converter instruction manual is not always given to the buyer anyway.
Voltage Drop Problems
The original electrical converter cannot be modified. Replacements that charge at higher voltage also charge faster. That, however, can only partially assist.
The limitation is that most converters produce 13.6-13.65 volts. Lighting and appliances, however, need 11.8 to 12.7 volts. Converters are intended for RV owners having 230 volts most of the time. That 13.6-13.65 volts thus enables makers to use cable far thinner than needed when running from a 12-volt battery. As a result, part or all of that RV’s related cable deliberately drops up to one volt. That’s fine on 230 volts. But not when battery powered.
At least 80% of all RVs globally have these converters. In the USA it’s a probable 95%. Most RVs using such converters have that lightweight cabling: it’s much cheaper.
Replacing the converter
Electrical converters in RVs work well for their intended usage. They do not work well for extended free camping. If free camping is in mind there is little choice but to replace them.
Replacing the converter by a high-quality battery charger and dc-dc alternator charging assists. But if the RV has lightweight wiring, some needs upgrading. This includes all charging circuit and battery cabling, fridge cabling (essential), and the water pumps. If LEDs are not fitted, change whatever is. As LEDs draw far less current, the existing cable is fine.
Increasing battery capacity (alone) is pointless. The converter’s charging is inadequate for any purpose other than intended.
A high-quality battery charger charges the battery much faster. The appliances (particularly any compressor fridge), however, will not work as intended unless that cabling is upgraded.
With decent wiring in place a good solution is to install a battery management system. These include the 100% recommended dc-dc alternator charging, plus solar regulation. Many have also a 15-40 amp multi-phase charger. Plus energy monitoring.
You can alternatively use separate units. These may be a dc-dc alternator charger, and a serious multi-stage 110/2130 volts battery charger. Buy all from the same vendor to ensure they are 100% compatible.
LiFePO4 batteries assist
LifePO4 batteries in RVs produce from a typical 13.1 volts to about 12.9 volts. Whilst lightweight cabling imposes a voltage drop, that 13.1-12.9 volts is much higher than with other types of battery. These batteries also charge to at least 80% from 13.65 volts. They do so, however, very slowly. It’s better by far to scrap the converter and install a high-quality charger.
For the technically minded
A typical converter works much as shown below. Most are 110/12 volt or 230/12 volt transformers. The have a full-wave bridge rectifier and possibly smoothing capacitance.
Some include a direct 12-volt input. As shown that ‘input’, however, is a few centimetres of wire plus a diode (to prevent reverse flow). That diode nevertheless introduces up to 0.6-volt drop. This reduces alternator charging to snail’s pace. 
Typical basic converter. Pic: Copyright rvbooks.com.au
Most converters float the battery across that 13.60-13.65 volts output. They do so via a sensor, that typically limits float current to 0.8-1.5 amps. An override enables charging at higher current if the battery drops below a typical 10.5 volts). It so however at that unregulated 13.65 or so volts. This is not nearly enough for deep and rapid charging.
A few converters include multi-phase charging, but usually via fixed voltages for bulk, absorption and floating. They do not supply the constant current required for an effective bulk cycle.
Electrical converters in RVs – further information
See also Article Charge Batteries Faster and Deeper. It relates specifically to using converters for purposes for which they are not intended.
This subject is covered in depth in the author’s best selling book Caravan & Motorhome Electrics. It also covered (re solar) in Solar That Really Works (for cabins and RVs), and Solar Success (for home and property systems). My other books are the all-new Caravan & Motorhome Book and the Camper Trailer Book. For information about the author please Click on Bio.
These books have helped tens of thousands worldwide to make the right decisions. Any one of them will save you many times its cost.
Safe RV heating – use diesel or LP gas
by Collyn Rivers
Safe RV heating
This article is about safely heating travel trailers and motorhomes using diesel or LP gas. It explains how it works. It lists what is available. And moreover, how you can safely install it. To ensure safe RV heating correct installing is essential. Apart from carbon monoxide, there is furthermore a risk of oxygen deprivation. Furthermore, for a technical and medically-referenced explanation see Gas Risk in Travel trailers.
Safe RV heating
Diesel or LP gas-powered heaters draw fresh outside air into a tiny sealed furnace. The fuel burns in this furnace. Air is blown across the furnace’s hot outer skin. Flexible hose directs the heated air as required.
For safe heating, you must air-seal the furnace unit from the living area. This is essential. Fumes from burning fuel are expelled outside.
The Webasto diesel space and water heater installed in a TVan.
Several manufacturers make RV heating products. These include Eberspacher (‘Dometic’ in Australia), Webasto, Truma and Diesel Heating Australia. All are available as space heaters. Moreover, some are space plus water heaters. The smallest produce ample heat for medium-sized RVs. The next size up heats a cabin, or a large RV.
Webasto space heater. The Dometic unit is virtually identical. Truma’s is similar but taller. Pic: Webasto.
Space heater
The units are about the size of a brick. They mount with intake and exhaust outlets downward. A 12-volt pump draws from a typically 10-litre tank. Alternatively, you can tap into your vehicle’s tank. Some may have a larger separate water tank or radiator. Furthermore, most have a control panel that you locate where convenient.
The Genesis II combines space heating and water heating. Pic: Diesel Heating Australia.
I used a Webasto diesel unit in outback Australia. There, after sun-down, temperatures drop quickly. Often to below freezing. On its lowest heat setting, the heater kept the interior at 24º C. It used a litre per five hours.
The unit was slightly noisy. You can, however, reduce by adding an inlet silencer. Reports indicate all brands are much the same.
The Truma LP gas space heater. Pic: Dometic Australia.
Space/water heaters
Combined space/water heaters initially heat glycol. The hot glycol flows through an exchange unit. That unit heats water to a scalding 80º C. A tempering valve is legally required. It mixes cold and hot water. This limits the water to 50º C. Water heating water takes about five minutes.
The Webasto space/water heater. Pic: Webasto Australia
See also Gas Risk in Travel trailers on the Articles section of this website.
Further information
RV heating is covered in The Camper Trailer Book, Caravan & Motorhome Electrics and Caravan & Motorhome Book. Our other books are Solar That Really Works (for cabins and RVs). Furthermore, Solar Success is for home and properties.
These books help tens of thousands to make the right decisions. Moreover, any saves you many times its cost.
For information about the author: Click on Bio.
RV electrical wiring – twin-wire or chassis return – here’s why twin-wire is usually better
by Collyn Rivers
RV electrical wiring – Twin-Wire or Chassis Return
Twelve-volt RV systems require two electrically conductive paths between the battery and whatever light or appliance they energise. This can be done in two different ways. The first is to use a separate lead for each. The second way, twin-wire or chassis return is to use the RV’s metal chassis as part of one of the leads. This is primarily to save cost. Copper is very expensive – the chassis is already there.
This article strongly recommends using the twin-wire connection. This is particularly so for campervans and motorhomes. Furthermore, this article explains why. Moreover, it shows how to avoid known problems.
Twin-wire has one conductor (usually red) the positive lead. The other conductor (usually black) is for the negative lead. The two wires may be separate. Or within one sheath.
The chassis as a conductor
So-called chassis negative return uses the RV’s metal chassis as the common negative conductor. A single light wire from each appliance connects to the chassis. A heavy cable then connects the chassis to the battery’s negative terminal. A single positive wire only is thus needed most appliances. This saves the RV maker a few dollars.
Chassis negative return works well initially if the chassis connections are correctly made. Many are, however, exposed to damp. They then corrode. After a year or two connection may become intermittent. Or fail totally.
After a time negative return connections may look like this! Pic: inspectapedia.com
Avoiding RV electrical problems
Faulty connections cause many RV problems. Auto-electricians dislike them as faults may be intermittent. Not all RV makers use chassis return. Those that do, however, make such connections thoroughly. Moreover, they protect them against dirt and damp.
Chassis return RV electrical wiring is rarely an issue. It is usually done thoroughly with the chassis terminals welded to the chassis. Most problems arise with owner-added connections – usually via self-tapping screws – that rust over time.
Electrolysis
The major issues with chassis return particularly affect powered vehicles. It can cause so-called ‘electrolysis’. This is a particularly invidious form of corrosion.
Chassis return’s intention is for all negative current to flow only via that chassis and the heavy cable to battery negative. Electric current, however, attempts to flow via every metallic path. It does this mostly via the chassis. Problems occur, however, if that main earthing cable loosens. Or its connection corrodes, also if inadequately sized. Return current then seek paths of lesser resistance. This is often via the radiator and water pump. Both contain different types of metal. These are mainly attacked. As current flows through them they corrode.
Single-core (usually black) is used for chassis earthing. Red is used for positive. A few companies, however, use black (+ve) and white (-ve). The twin-core cable shown here is used for circuits that do not use chassis return.
This issue is often caused following vehicle front end repairs. A spot-light (or worse a winch) may have originally had its negative lead strapped to the chassis. The repairer, however, may re-connect to the closest nearby metal. That can result in part of the current flowing via the radiator. Or the water pump. If that happens, corrosion is virtually inevitable.
Vehicle makers require routine service checks for electrolysis. It is done by measuring the voltage (to earth) of the radiator fluid. It should zero. For a fuller explanation ‘Electrolysis Corrosion in Vehicles’.
RV electrical wiring – further information
Caravan & Motorhome Electrics covers every aspect of designing, specifying and installing RV electrical wiring. It also covers every type of lighting and appliances, plus solar and charging systems.
Solar that Really Works does likewise re solar for cabins and RVs. Solar Success is for homes and properties. Caravan & Motorhome Book covers every aspect of RV use. For author information: Click on Bio.
Connecting travel trailer batteries – there’s no magic way of doing it!
by Collyn Rivers
Connecting Travel Trailer Batteries
Connecting travel trailer batteries is often misunderstood. This article explains what’s possible, and why and how to do it successfully.
A typical travel trailer has an ongoing need for energy. And an occasional need for (high) power. Knowing the difference between energy and power truly assists.
Energy is the ability to perform work. It was originally estimated that a brewery horse could typically lift 33,000 pounds one foot in one minute. That amount of energy was thus called one horsepower. This now mostly expressed in watts. (About 750 watts is one horsepower).
Power is the rate at which energy is used to perform work. If that 750 watts is drawn for one hour, it’s expressed as 750-watt hours.
That brewery horse’s one-minute lifting is equalled, in a few hours, by a child. Horse and child exert equal energy. But the horse needs far more power.
Battery usage is similar. A starter battery is thus horse-like. It can exert high power. Starting a car engine however, takes only two/three seconds. The energy expended is tiny. It’s about that used by a 12 watt LED in ten minutes.
A deep cycle battery, contrarily, is akin to a marathon runner. Less ‘power’ but energy can be expended far longer.
Connecting travel trailer batteries – ensuring enough energy and power
As explained above – most travel trailer batteries have two main (but different) requirements.
1. Enough power to cope with high peak loads.
2. Enough energy to cope whilst away from 230 volts etc.
This can be addressed in two main (but different) ways.
Different batteries – different characteristics
Increasing battery capacity increases available power. And, virtually by definition, more energy. There are, however, downsides. You must, for example, have the ability to recharge them. That charging must be both deep and fast.
Lead-acid deep cycle batteries are heavy. Twelve-volt versions weigh about 25 kg/100 amp hour. Their life is greatly reduced by frequent deep discharging. Their plus side is (relatively) low price. Plus ready availability.
AGM batteries are a compromise. They are physically rugged – thus suited to off-road use. AGMs can supply higher power than conventional batteries. They maintain charge far longer (12 months plus in cool climates). AGM batteries, however, are even heavier than conventional batteries. Discharge needs limiting to about 50%. If exceeded, their life is thereby curtailed. And they cost a lot more. (Gel cell batteries are similar – but less often used.)
Any 12-volt LiFePO4 battery above 18 amp-hour supplies RVs peak power with ease. The energy capacity needed, however. is slightly less. This is because they can be routinely discharged to 10%-20% remaining. Another benefit is that (in RV use) they rarely drop below about 12.9 volts. They are about 35% of the weight and bulk. On the downside, they cost far more. They must also have effective individual cell management. Buy only from vendors who truly understand them. These are, however, rare.
In practice, a 300 plus amp hour AGM battery will provide the peak power required for any RV. It also has ample energy capacity. AGM batteries are thus a good choice if space and weight permits
Connecting travel trailer batteries
To ease handling, (or obtain higher voltage, or higher current) batteries can be connected together. There are two main ways of doing so.
Series: consecutively positive to negative. Total battery voltage is the sum of each individual battery voltage. The total current is that of the battery that produces the least current. For example, were all batteries 100 amp hour, but one 50 amp hour, the total output would be 50 amp hour.
Parallel: positive to positive, and negative to negative.
Here, all batteries must be the same voltage but can be of widely different capacity. The available current and capacity is the sum of each individual’s current and capacity.
When connecting travel trailer batteries in parallel, it is, for example, just fine to parallel a 12 volt 10 amp hour battery across a 12 volt 500 amp hour battery bank. The result is a 12 volt 510 amp hour battery bank.
![Connecting [cara] batteries - there's no magic way of doing it! - electric vehicle batteries,book on batteries,electric car batteries,lithium ion batteries for electric cars,electric car battery technology,how long do electric car batteries last,electric vehicle battery life](https://solbsau.centrails.com/wp-content/uploads/2014/09/Battery-shed-coconut-well-reduced-jpg.jpg "Connecting [cara] batteries - there's no magic way of doing it! 162")
This battery bank (at the author’s previous all-solar powered property outside Broome, WA) had 16 batteries, each of 12 volts and 235 amp-hour. Each level has four such batteries in series. All four rows are parallel connected.The output is thus 48 volts and 950 amp-hour. That’s 45,120-watt hours (45.12 kW/h). Pic: rvbooks.com.au
Parallel connecting batteries is safe
Contrary to common belief, this is safe. Like good socialists, each (battery) will thus take according to its need, and supply according to its capacity. See Interconnecting batteries in series or parallel re advised limits.
To increase both voltage and current, you parallel identical strings of series-connected batteries. Here, the voltage is that of any one string. The amp-hour capacity is the sum of all the batteries’ capacity. Doing so, furthermore, is routine in large solar systems. They are typically 48 volts upwards.
Connecting batteries in series (end-to-end) thus increases the total voltage. Connecting batteries in parallel increases the total current.
In every case, their total energy (i.e. watt-hours) is the sum of each battery’s energy so connected.
There is no magic way of increasing it.
Connecting travel trailer batteries – 6 volts or 12 volts?
Most travel trailers and motorhomes have 12 volt systems. As batteries are heavy, some owners prefer 6-volt batteries. To obtain 12 volts they are series-connected (positive to negative) as below. This results in the same current (as each 6-volt battery) but twice the voltage.
Series connection. If each 6-volt battery is 100 amp hour (600-watt hour) two series-connected such batteries hold 100 amp hour at 12 volts (1200 watt-hour). Pic: rvbooks.com.au
If more capacity is required, further pairs of so-connected batteries are then wired in parallel as shown below. 
Here, four 6 volts 100 amp-hour batteries can hold 200 amp-hours at 12 volts (2400 watt-hours). Similar connection (but using 12-volt batteries) are used to obtain 24 volts in converted coaches with 24-volt alternators. Pic: rvbooks.com.au
A few travel trailers have only one 12 volt battery. Most, however, have two 12 volts, 100 amp-hour batteries. The result is 200 amp hours (2400 watt-hours.)
If four batteries, each of 100 amp-hour are parallel connected, total capacity is thus 400 amp hours (4800-watt hours). 
Typical battery bank for a largish RV. Four 12 volt 100 amp-hour batteries store 400 amp-hours at 12 volts (4800 watt-hours). Pic: rvbooks.com.au
Probable requirements
For most RVs, the highest (domestic) power need is likely to be a microwave oven. They draw about 130 amps for 5-15 minutes, typically via an inverter.
Any LiFePO4 battery used as the main RV supply will cope with ease. Such power can just be met by a 12 volt 200 amp-hour AGM battery. But 300 plus amp hour is preferable. Some owners attempt this with 200 or so amp hour deep cycle lead-acid batteries. They will supply such power for a short time, but doing so repeatedly shortens their life.
Connecting travel trailer batteries – Summary
The best way to increase available power for the same energy capacity is via batteries capable of doing so.
Conventional lead-acid deep cycle batteries are the least so-capable. AGMs are better. If bulk and weight are not a handicap, a 300-400 amp hour AGM bank readily provides RV energy typically needed.
The highest energy and power (by far) is from lithium-ion (LiFePO4). Any such battery will have ample to drive whatever you wish. They also have more available energy capacity. They are however costly. Furthermore, they need specialised installation and charging.
Connecting travel trailer batteries – further information
Batteries and their charging are complex subjects. Caravan & Motorhome Electrics explains battery charging in depth.
If you liked this article you will like my books. They are technically accurate – yet in plain English. Other books are the Caravan & Motorhome Book, the Camper Trailer Book, Solar That Really Works (for RVs), and Solar Success (for homes and properties).
Ultra-light travel trailers – they are rare but feasible. Here’s how to do it
by Collyn Rivers
Ultra-Light Travel trailers
Ultra-light travel trailers and fifth-wheelers are rare but feasible. Here’s how it is done using hi-tech materials. One, over 9 metres, was under 2000 kg (4400 lb).
Australia’s Glenn Portch spent 20 years experimenting and building ten ultra-light fifth-wheel travel trailers. His own 11.3-metre unit weighs 3200 kg (7050 lb). Its payload (of an extraordinary 1200 kg [2650 lb]) allows him to include his Harley Davidson motorcycle with ease. The last of the eight he made is 9.1 metres. It was originally under 2000 kg (4400 lb) but the buyer insisted on a granite kitchen bench-top!
Glenn’s ultra-light travel trailer research had no financial motive. He made them to see what was possible. The other nine were sold at close to cost price. By doing so, Glenn has shown that ultra-light travel trailer design is feasible.
Glenn’s own ultra-light Navigator is 11.3 metres. It weighs 3200 kg (7050 lb) and its carrying capacity is 1200 kg (2650 lb). Pic: Glenn Portch
Glenn’s first engineering was in the 1980s. He sought a pair of up-market loudspeakers. Most, however, were costly, available only in black, and lacked styling. He researched extensively. Then, using the very best available components, designed and built them himself. They had gloss white enclosures with black granite overlays. A Sydney hi-fi shop owner (that I also know) asked if Glenn to build more.
Glenn and his (then) partner set out to build the world’s best. Within a few years, they exported their (Audio Definition) loudspeakers to nine countries. They had 14 local dealers. The products were not cheap. Their sound quality necessitated top-quality components. The superb cabinet finish demanded years of research and testing. They made lower-priced models too, but the top ones were $35,000 a pair. They were so successful they won many top world awards.
Ultra-light travel trailers – fifth wheel format
Glenn later became interested in travelling around Australia. Often in the USA – researching audio, he could see that fifth-wheeler travel trailers were rapidly gaining acceptance. The fifth-wheeler configuration (and its inherent towing stability) appealed to his knowledge of the physics involved. But whilst liking the concept, those available seemed unnecessarily heavy. Some absurdly so. So, once again Glenn decided to build his own. But ultra-lightly!
Ultra-light travel trailers – strength
Despite aluminium-framed aircraft since 1900, many travel trailer builders assume weight confers strength. Many a locally-made travel trailer‘s floor and fit-out are of heavy plywood. This adds little structural strength, yet considerable and unnecessary weight. It is seriously counterproductive. Such weight necessitates a heavier chassis, suspension and tyres to carry it. As a result, most US and Australian-built travel trailers are heavy, yet not necessarily strong.
A few local makers use lightweight body construction. Most, however, retain a heavy (yet not strong) chassis. They are still lighter -yet still unnecessarily overweight.
Ultra-light travel trailers – chassis
Before designing and building himself, Glenn approached many travel trailer builders. All claimed it could not be done. ‘Aluminium tends to break mate’. But, as Glenn points out, steel used incorrectly may also break. He suggests anyone truly believing aluminium used correctly breaks, to ‘bear in mind that Boeing’s aircraft are hardly based on rolled steel joists’.
A partially completed main chassis – the triangulated design is clearly seen. Pic: Glenn Portch
Some trailers have alloy chassis – but of ‘C’ section, or I beams 6-10 mm thick. Their resultant weight and poor torsional rigidity, however, defeats the point of using alloy. But promotionally it’s good.
This end view of a partly-completed ultra-light travel trailers chassis shows triangular bracing. Pic: Glenn Portch.
Glenn Portch’s concept employs ultra-light three-dimensional trellis-like chassis of light box-section aluminium. A composite material floor, and a similar (frameless) body bonds to that chassis. This allows slight flexing to cope with road irregularity stresses. His ultra-light travel trailers are thus similar to aircraft and ultra-yacht design. It enabled his aim, of about 200 kg/metre for fully equipped units, to be achieved.
Ultra-light travel trailers – strength
For anyone doubting the strength and durability of Glenn’s ultra-light travel trailers approach, consider this. The first (of eight) built had (in 2018) already exceeded 300,000 km. That’s 23 times more than the average travel trailer‘s 13,000 or so km a year.
Ultra-light travel trailers – interiors
Glenn’s overall ultra-light monocoque concept handles forces via the external skin. Internal fittings too structurally brace. Floor, shower and divisional walls, are all MonoPan. This is an ultra-strong fibre-reinforced thermoplastic skin bonded to a similar core. The outer skins provide structural strength and resist impact. An ultra-light core separates the skins, enabling major resistance to bending.
The cabinetry’s cube-lock square aluminium extrusion is held together by plastic corner locks. These are riveted and glued to the main structure. This, working in unison with the monocoque shell, further adds strength. Glenn makes the drawers out of 1.6 mm aluminium. Runners rivet them in place within the cube-lock structures.
Benchtops are 30 mm Monopan, laminated, and with Jarrah timber edging. The Monopan is finished inside and out with automotive two-pack paint. ‘It withstands weathering better than bare fibre,’ says Glenn.
This is the last and lightest built of Glenn’s builds. It is 9.1 metres – yet can be built at under 2000 kg (4400 lb). Pic: Glenn Portch.
The last and lightest
The last built (in 2015) is 31 ft (9.1 metres). It is far from an average fifth-wheeler (that typically has a 100-litre plastic water tank and cassette toilet).
This one is sumptuously fitted out. It has 380 amp-hour battery capacity, plus 450 watts of solar. The 1500 watt Trace inverter has an inbuilt 75-amp charger. There is a 219-litre compressor fridge, 400 litres of freshwater, 300 litres of grey-water, plus 220-litre black water tanks.
Without its AL-KO suspension, the chassis weighs a mere 200 kg (440 lb)! Had a traditional 19 mm plywood floor been used, that alone would add some 200 kg (440 lb). Yet have zero structural strength. Traditional construction also necessitates a heavier chassis, wheels, tyres and brakes to carry it. All add yet pointless weight.
The completed unit originally weighed under 2000 kg (4400 lb)! The buyer, however, sought heavy additions, including dining, vanity and bedside tables of solid Jarrah. Also sought was a full-size double domestic sink and 6 kg (13 lb) capacity washing machine. Plus a china toilet and macerator. There is also a hospital-grade vinyl floor that weighs as much as the 30 mm Monopan it covers!. Required too was a slide-out BBQ, beneath a 5.4-metre awning.
Gas bottles are set within the chassis rails. Pic: Glenn Portch.
Despite all this, the unladen unit weighs only 2260 kg (4980 lb). Its permitted on-road weight, however, is 3800 kg (8375 lb). This leaves an extraordinary 1540 kg (3400 lb) for water and personal effects!
Ultra-light travel trailers – proving them possible
Glenn is constantly asked to build ultra-light travel trailers for general sale. His main aim, however, was to show (and prove) what he felt possible. He did not do this for profit, but out of intellectual interest. Developing and proving the concept took over 20 years. That he has now done. He considered consulting if any manufacturer was interested. But, a now five years later, none appear to be.
Meanwhile, local travel trailer makers need to start thinking hard about far lighter travel trailers. With rare exceptions, the era of heavy tow vehicles is rapidly passing.
Now, Glenn enjoys using his own fifth-wheeler. He spends much the Australian winter up in the tableland outside Cairns.
I thank Glenn Portch for so generously sharing his knowledge. This article (originally published in 2017) has already inspired many self-builders.
Further information
For further information on fifth wheelers see https://solbsau.centrails.com/fifth-wheel-caravans-are-safer/ Also https://solbsau.centrails.com/caravan-and-tow-vehicle-dynamics. The topic is covered also in the Caravan & Motorhome Book. My other books are: the Camper Trailer Book, Caravan & Motorhome Electrics, Solar That Really Works (for RVs) and Solar Success (for homes and properties). For author information click on Bio.
Battery ventilation is vital – why take any risk?
by Collyn Rivers
Battery Ventilation
All lead-acid batteries, AGMs and gel cells, generate explosive gas. Even though most are sealed, makers stress that battery ventilation is vital still. Confusion exists over this. Around 2000, some battery makers began to claim that no ventilation was required. Or, ventilation is advisable but not necessarily essential. They withdrew this advice, however, shortly after. Many batteries thus have a warning notice as below.
Despite warning notices like this, many RV builders install batteries in unventilated compartments. In 2012, one threatened criminal defamation when I published that ‘battery ventilation is vital’. The company withdrew only when shown evidence the batteries they were fitting in their own products had such notices.
Explosion risk
Hydrogen lacks colour or smell. Without instrumentation, a human cannot detect it. Unsealed batteries smell whilst charging, but that odour is not hydrogen.
Many batteries have an acid/water mix called an electrolyte. If overcharged, that liquid produces explosive hydrogen. In a typical battery enclosure with about 10 litres of free air space, a 10% (explosive) concentration builds up within 60 seconds. When mixed with air, ignited hydrogen typically starts fizzling at a concentration of about 4%. If the concentration exceeds 10% a tiny spark causes it to explode.
Sealed batteries cope with low levels of overcharging. To prevent an explosion, they have normally sealed vents. These open when pressures reach dangerous levels. As long as the batteries are ventilated (and there is no source of ignition) this gas typically dissipate harmlessly.
Lead-acid battery explosion is rare. It can however blow an RV apart. One (Australian) RV maker, whose product lacked ventilation, blew out the floor of his very own, through just that.
Assuring basic ventilation is so easy it seems ridiculous not to provide it. Let alone (as some do) to argue against it.
An exploded battery is an ugly sight. Pic: http://www.rayvaughan.com
Hydrogen only explodes when ignited. An almost invisible tiny spark, however, does so. Common sources include insecure terminal clamps and cables. Also, battery connectors that work-harden and crack. Sparks can also be caused by any electrical or moving device. Worn bearings may do so. Battery chargers, isolating relays etc, should never be installed in battery enclosures. Such battery ventilation is vital.
Venting details
The battery enclosure must enable fresh air to enter at its base. The (lighter) hydrogen must be able to escape to atmosphere via unrestricted outlets at the enclosure’s very top. The RV industry has no standards regarding this. General practice, however, is to provide a few 25 or so mm holes at the top. They are needed to the very bottom.
In 2003, the (then) Sustainable Energy Industry Association suggested the following minimum. The size given is for each vent (top and bottom).
Area in sq cm = 0.006 X ‘n’ X I.
Where ‘n’ – the total number of cells in the battery/s (for this purpose each cell is nominally 2.0 volts)
‘I’ = maximum charging rate in amps.
For example a travel trailer with two 12 volt batteries (each of 6 cells) and maximum charging rate might be 50 amps. Then A = 0.006 x 12 x 50 = 3.6 sq cm. The above is a minimum requirement. Ventilation can thus be one or two slots top and bottom. Each should be about 5 cm by 1 cm.
Naturally vented enclosures have been criticised. Decades of experience, however, indicate they are adequate. Wind, however, can generate areas of high pressure around exit vents. This can prevent gas from escaping. This is less of an issue if adequate lower vents are provided. But many an enclosure is vented only at the top. If yours is like that, cut a few holes at the very bottom.
LiFePO4 batteries
These batteries use a technology that is different from lead-acid. These batteries can and do explode. When they do, they typically emit dense white smoke. This strongly irritates and may harm the respiratory tract, mucous membranes, eyes, and skin. The electrolyte reacts with moisture to form hydrogen chloride and sulphur dioxide. Some also release bromine and chlorine. There are also fire risks if they are overcharged. This is due to the flammable properties of volatile organic substances.
So here too battery ventilation is vital. Vendors offer little advice re this. It seems prudent, however, to house them much as with lead-acid batteries. Ideally using fire-proof materials. (See also Article Lithium-ion batteries in travel trailers.)
Battery ventilation is vital – summary
There are no legally enforceable (RV) standards in this area. This article can thus only state that battery makers stress battery ventilation is vital. Some explain why.
There is little or no risk if batteries are housed in well-vented enclosures. With sealed batteries, the risk is not high. It exists however if they are within (say) a closed bed base that traps gas. Eliminating this risk consist of little more than cutting slots, or drilling holes. So why not do it?
Further information
For information on batteries and battery charging see: AGM batteries for travel trailers, Lithium-ion batteries in travel trailers, and Speeding battery charging from generators.
In-depth coverage of batteries and battery charging is included in my books Caravan & Motorhome Electrics, Solar that Really Works! (RV-related), and Solar Success (homes and properties). My other books are the Caravan & Motorhome Book, and the Camper Trailer Book. For information about the author please Click on Bio.
This topic often arises on RV forums. If you feel this article might assist others, please consider posting this Link to it on the relevant forum thread.
How much solar input – here’s how to find out
by Collyn Rivers
How Much Solar Input
Knowing how much solar input is coming in like measuring rainfall. It uses units called Peak Sun Hours instead of inches or millimetres.
Much as a rain gauge shows a day’s rainfall in millimetres, knowing the day’s number of Peak Sun Hours indicates how much solar input there is each day. This article, by Collyn Rivers (RV Books), explains all.
How much solar input
Imagine an open drum that ‘collects and concentrates’ sunlight (rather than rain). When full, that drum contains one Peak Sun Hour (1 PSH). It is likely to ‘fill’ in one hour in Alice Springs around noon on most days but takes longer early and later in the day. In a Melbourne mid-winter, filling one drum takes most of one day.
Solar is even used on the world’s highest lake (Lake Titticaca) in Peru.
A Peak Sun Hour is a solar industry unit. It is that amount of sunlight that averages 1000 watts per square metre for one hour. For example, 4 PSH/day is as if there were four hours at 1000 watts per square metre. About 75% is likely to be over the two/three hours each side of noon, and 25% over remaining daylight hours. Translating that into solar module input is (relatively) simple.
In theory, a solar module of one square metre captures 1000 watts per PSH a day. In practice, it’s far less, because solar modules are only 14-21% efficient.
Depending on latitude, season and weather, PSH in Australia varies from 2.0 (south in winter) to 7-8 (in central and southern areas in summer). Northern Australia has less variation: from 5.5 in winter to 6.5 in summer. This fools visitors assuming the opposite and wondering why there’s less than expected.
Based on NASA data, this map shows probable (averaged) mid-summer output (in Peak Sun Hours). copyright © rvbooks.com.au
How much solar input – worldwide
Meteorological offices worldwide have maps that show how much solar input – but in scientific units. My own are based on a ten year running average (from NASA data) and updated when needed. The current summer data is shown here. There are inevitable variations, but they provide a reasonable guide to how much solar input for most years.
Optimising solar output
The further north or south, the lower in the sky the sun tracks east/west. To optimise solar input, solar modules face into the sun at midday. They face due north (in the southern hemisphere) and south (in the northern), tilted at the location’s latitude angle. To establish that angle, Google your location plus ‘latitude’. In Australia’s far north, the sun tracks close to, or overhead part of the year, so close to horizontal captures the most sun. For homes, avoid having modules totally flat – or dust settles. And so do birds and small animals.
Tracking mechanisms enable solar modules to face directly into the sun. They work but are complex and costly. It is cheaper and simpler to accept the loss. Adding 10%-30% more solar capacity compensates. Further, the sun’s effect is far from a ‘shaft of light’. It is often diffused – so minor non-alignment makes little difference. Tilting or tracking increases output if/when the module is producing less than its capable maximum.
The Australian Solar Radiation Data Book has full data. It shows that for Adelaide (35º south) in January in solar input differs, between horizontal mounting and the optimum 10º tilt by only 0.16%. Even 20º error makes only 4% difference. Over a year, solar input there, with modules at the optimum 30º provides an average gain of about 8% compared with horizontal mounting. Variations of plus/minus 20º in north-facing or tilt cause less than 5% difference.
The now less common amorphous modules are less heat affected, but all others lose power when they become hot. This loss is typically by 5% for each 10º C.
Solar input for marine and RV use
Data above is for fixed locations, or those travelling mainly in summer. A different approach is needed whilst travelling extensively in Australia, or at varying times of the year.
For distance travelling, you need solar capacity that is excess much of the time. Or if preferred, using solar to complement a generator-based system (or vice versa). An effective rule is assuming 2.5 to 3.0 PSH for all areas except Hobart and Melbourne’s midwinter. There, under 2 PSH is common in June/July.
A reliable guide (for existing systems) is that, the batteries are fully charged by midday most days year-round there’s insufficient up north except in mid-winter.
What solar modules really produce
The promotional output cannot be achieved in typical use. Just why is explained below. In practice, if used with a cheap solar regulator, most solar modules produce about 70% of that seemingly claimed. A Multiple Power Point Tracking (MPPT) solar regulator lifts that to about 80%.
Your most probable input is daily PSH (for the area times 70% of what was claimed. Or with the MPPT unit, 80%-85%.
Technical explanation (why solar makers do not get sued)
Typical solar modules produce maximum power (volts times amps) at around 17.1 volts. Charging a 12-volt battery, however, requires 13.0-14.7 volts. With basic solar regulators, all between that 17.1 volts solar output and the charger’s needs is not accessible.
An MPPT regulator ‘juggles’ available volts and amps thereby optimising watts. This recovers of that otherwise unavailable. It is particularly effective when the battery is low in charge, and during early and late hours of the day. Dismiss claims of MPPT ‘increasing’ energy by 25-30%. It recovers about 10%-15% over a day of that otherwise lost. Enough to justify its use but generally less than claimed.
How much solar input in tropical areas
Many owners assume solar input in tropical areas is higher year-round. This is not so. Input during tropical winter is typically 5-5.5 PSH, and 6.0-6.5 PSH in summer. There can be major issues with fridges that run from solar because it stays hot all night as well. Energy usage is up to 40% higher.
Further information
For a full explanation see my Solar That Works (for cabins and RVs). Solar Success (for homes and properties. See also Living With Solar. Details of the author’s own (Broome) system see All Solar House.
All aspects of RV usage is in the Caravan & Motorhome Book. For RV electrics – Caravan & Motorhome Electrics. See also the Camper Trailer Book. For author info click on Bio.
If you find this article helps, adding this Link assists others on forums.
How to Reverse a Travel trailer
by Collyn Rivers
How to Reverse a Travel trailer – the basics
This How to Reverse a Travel trailer article will guide you through how to do it yourself. Learning how to reverse a travel trailer is not hard to do. Ongoing practice then assists.
How to Reverse a Travel trailer – if possible start with a box trailer
It is better to learn by towing a box trailer. It seems less daunting and costs less to fix if you damage it. To many first-time tow-drivers surprises, however, long travel trailers are easier to reverse than short ones. This is because a longer distance between trailer axle(s) and the tow hitch enables the trailer to respond more progressively.
Learning how to reverse a travel trailer only seems difficult at first. This is because, when reversing, the tow vehicle’s overhung hitch causes the travel trailer to turn in the opposite direction to that of the tow vehicle. Once that is realised (and its implications understood) all becomes clear. From thereon it just needs practising.
A good place to do so is a close-to-empty car park and well away from all other vehicles. Do everything slowly because a reversing travel trailer amplifies every movement of the steering wheel.
How to Reverse a Travel trailer – practice reversing in a straight line
Start by teaching yourself to practice in a straight line. This is likely to be harder to do than expected. Turn the steering wheel by only tiny amounts, while watching the travel trailer via the wing mirror. Once you have grasped that, do the same but in a slight curve. This will entail ongoing minor corrections because the turning circle self-tightens.
If possible have someone stand well behind the rear of the travel trailer (but not in its path). You need to able to see that person through your wing mirror. It also helps to be able to communicate via CB radio, mobile phone or hand signals – or whatever works for you.
Ask the helper to advise only what is happening that is out of your sight, e.g. distances, and when to stop if necessary – so as not reverse into a brick wall or up a kerb. It is then up you to work out what to do.
How to Reverse a Travel trailer – the jack-knife point
The most common initial problem is inadvertently reversing in a progressively tightening curve such that tow vehicle and trailer end up at close to a right angle. If that happens the driver must stop and drive forward, or the rig will be damaged.
This so-called jack-knife angle is different for each trailer and tow vehicle combination and can only be determined by trial and error. It is well worth checking this.
To determine your trailer’s jack-knife point find a large safe area. With a partner assisting, very slowly reverse your rig, turning the steering wheel slightly (such that the trailer turns toward your side). As you do so watch the trailer’s movement constantly via the wing mirror.
Do this a few times. Each time turn the steering wheel a little further. As you do this you will find that the tow vehicle and trailer become increasingly close to a right angle. You will also find there a safe limit to this. If you overdo the turn, the trailer’s draw-bar will jam against the rear of your tow vehicle. If you keep turning you may damage both the tow vehicle and travel trailer. If necessary, adjust your wing mirror so that the ground at the rear of your tow vehicle is visible.
How to reverse a travel trailer. A towing course is not essential but builds reversing confidence – Pic: Tow-Ed
How to Reverse a Travel trailer practice makes perfect
While learning how to reverse a travel trailer may seem daunting at first, with practice, you will be able to align your trailer to wherever it will fit. You are likely also to reduce the severity and number of steering wheel movements, making reversing quicker and smoother. After a time it becomes a natural action.
Take every opportunity to practice how to reverse a travel trailer where it is totally safe. You will progressively become proficient and relaxed about doing so. Alternatively, consider taking an initial lesson or three at a driving school that specialises in teaching travel trailer towing. All include learning how to reverse a travel trailer. They are readily found via Googling.
How to Reverse a Travel trailer reversing a fifth wheel travel trailer
Reversing a fifth-wheel travel trailer is as almost as easy as reversing a motorhome. If you are used to driving a long vehicle, it is a virtually self-obvious technique that can be acquired within minutes.
Variable voltage alternator problems with travel trailers – how to fix
by Collyn Rivers
Variable Voltage Alternators
Variable voltage alternator problems with travel trailers and motorhomes arise when charging auxiliary batteries. Here’s why and how to fix them. These alternators are, in particular, installed on many post-2013 vehicles.
Prior to the year 2000, alternators produced 14.4-14.7 volts, and a few close to 15 volts. This adequately charged travel trailer and motorhome auxiliary batteries. Furthermore, where it did not, voltage boosting assisted.
Typical smart alternator – note extra-wide belt pulley. Pic: original source unknown.
Smart alternator problems with travel trailers – temperature compensating
These produce about 14.2 volts when the engine is cold. This decreases to about 13.2 volts as the engine warms. Lead-acid and AGM battery charging, however, needs up to 14.4 volts. Charging such batteries directly from these alternators is thus not effective.
Dc-dc alternator charging nevertheless fixes this problem. It accepts voltage available, boosting it to the levels required. This assists high current appliances that are far from the alternator or connected via a too thin cable.
All alternators must ensure the starter battery has charge priority. This is done by a voltage-sensitive relay. The relay precludes auxiliary batteries charging until the starter battery exceeds about 13.6 volts. It also disconnects if the starter battery voltage falls below 12.6. Used as above, temperature compensating alternators are not a problem with RV batteries.
Variable voltage alternator charging problems
Common since 2013, variable voltage alternator output is controlled whilst driving by the vehicles’ main computer. The voltage varies from 12.3 volts to plus 15 volts.
That 15 volts is too high for direct battery charging. It wrecks lead-acid deep-cycle batteries, gel cell and AGM batteries. Moreover, anything below 14 volts is of little charging use. When output falls below 12.6 volts the voltage sensing relay drops out. It consequently cuts auxiliary charging two to three minutes each time.
Some dc-dc alternator chargers will still work. How to do this varies as charger manufacturers develop solutions.
Smart alternator problems – regenerative braking
A vehicle at speed has so-called kinetic energy. Conventional braking dissipates that energy as heat. Rather than losing energy, braking is done by increasing alternator voltage. This loads up the alternator such that it acts as a brake.
Doing so requires the main (starter) battery to be normally 80% charged. The recovered energy brings the battery to 100% charge. Alternator voltage then drops to about 12.3 volts (or zero) until battery capacity falls to 80%. This cycle repeats every time the vehicle brakes.
When alternator voltage drops below 12.6 volts, the voltage sensing relay drops out. This isolates auxiliary batteries for minutes each time. Worse, ongoing bursts at plus 15 volts quickly destroy them.
Fixing smart alternator problems – regenerative braking
Companies tackling this include Redarc (Australia) and Sterling (UK). Both use the starter battery’s voltage to know what the alternator is doing and optimise auxiliary charging accordingly. This also protects auxiliary batteries against excess voltage.
How to know what alternator is which
Alternators used for regenerative braking are large. In addition, they may have multiple drive belts
To establish alternator type connect a multimeter across the starter battery. You may, however, need to extend the leads. Ensure they cannot be wound up by the drive belt. Have an assistant check voltage over a range of driving. Check whilst braking for a distance downhill. This may increase output to over 15 volts. (One BCDC maker suggests to do this by fitting a lighter plug to the meter lead socket. This is not a good idea. Some vehicles have them feed them at constant voltage!)
An output that drops below 12.7 volts whilst driving identifies variable voltage alternators.
Experienced auto electricians should be able to help. See also the dual battery system selector (that indicates RV alternator types etc) at https://www.redarc.com.au/calculator/dual-battery-calculator.
Variable voltage alternator problems with travel trailers – summary
Variable Voltage Alternators – these drop below 12.7 volts at any time whilst driving. They require a specialised BCDC unit that senses various voltage levels etc. None operate satisfactorily with a voltage sensing relay.
Fixed Voltage Alternators & Temperature Compensating Alternators. These produce above 12.7 volts whilst driving. Most dc-dc alternator chargers and voltage sensing relays should work. Contact their makers if in doubt.
Euro emission requirements (2020)
Increasingly rigid emission limits require vehicle makers to meet emission levels. For 2020 the target is 95 g/km of CO2 for all new cars. There is however a 12 month phase-in period such that 95% of new car to comply with the target during 2020 and 100%. This corresponds to fuel consumption of about 3.8 l/100 km.
The requirements do not specify how car makers achieve. It may or may not involve the alternator. These regulations may eventually preclude all alternator use for RV auxiliary needs. If/when, however, is unknown but can readily be resolved by using a fuel cell.
Note: Many vehicles with variable voltage alternators monitor load and charge via a cable between the vehicle’s chassis or, for chassis-less vehicles, from the metal bodywork and one terminal of its battery. This cable must not be altered in any way.
Our books include Caravan & Motorhome Electrics, the Caravan & Motorhome Book, and Camper Trailer Book. Solar That Really Works is for cabins and RVs). Solar Success is for home and property systems.
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Claims for dual-cab ute towing capacity mislead travel trailer buyers
by Collyn Rivers
Claims for dual-cab ute towing capacity
Claims for dual-cab ute towing capacity mislead travel trailer buyers. A dual-cab ute must weigh enough to keep a travel trailer steady. If not, the travel trailer tail wags the towing dog.
![Claims for dual-cab ute towing capacity mislead [cara] buyers - electric vehicle batteries,book on batteries,electric car batteries,lithium ion batteries for electric cars,electric car battery technology,how long do electric car batteries last,electric vehicle battery life](https://solbsau.centrails.com/wp-content/uploads/2020/07/DualCabUte-1-e1628471729878-1024x449.jpg "Claims for dual-cab ute towing capacity mislead [cara] buyers 178")
Pic: CarsGuide
For close to 40 years, Australia’s trailers exceeding over a laden 750 kg (1650 lb) was 72 km/h. The Royal Automobile Club (RAC) advised trailer weights not to exceed that of the tow vehicle. The RAC’s preference was a ratio of 3:4. We now have speed limits of almost 30-40 km/h higher.
It is now common for a 2500 kg (5500 lb) dual-cab ute to tow a 3500 kg (7715 lb) travel trailer. That is a ratio of 3.5:2.5. Many vehicle makers specify GCM (Gross Combination Mass). This is the maximum allowed weight of tow vehicle and trailer. In most cases, makers quote the weight of a totally standard vehicle. Here are a few examples. They show that claims for dual-cab ute towing capacity mislead travel trailer buyers.
Examples that claims for dual-cab ute towing capacity mislead
GCM 6000 kg (13,000 lb). Claimed tow capacity 3500 kg (7700 lb). Unladen weight 2247 kg (4954 lb). Payload 952 kg (2100 lb). If towing 3500 kg (7715 lb) that plus the ute’s unladen weight (2247 kg [4950 lb]) is 5747 kg (12,690 lb). This leaves only 253 kg (558 lb) for everything carried. That includes all fuel over 10 litres, driver and passengers. That all but empty 2500 kg (5500 lb) ute is towing an up to 3500 kg (7715 lb) travel trailer.
GCM 5910 kg (13,030 lb). Claimed tow capacity 3500 kg (7700 lb). Unladen weight 1969 kg (4340 lb). Payload 941 kg (2075 lb). If towing 3500 kg (7715 lb) that, plus the ute’s unladen weight, is 5469 kg (12,057 lb). This leaves 441 kg (972 lb) for everything carried. It is 2401 kg (5293 lb)
towing 3500 kg (7700 lb).
GCM 6000 kg (13,000 lb). Claimed tow capacity 3500 kg (7700 lb). Unladen weight 2118 kg (4670 lb). The payload 1082 kg (2385 lb). If towing 3500 kg (7715 lb) that, plus the ute’s unladen weight is 5618 kg (12,385 lb). This leaves 382 kg (842 lb) for everything carried. It is 2500 kg (5500 lb) towing 3500 kg (7700 lb).
GCM 5885 kg (12,975 lb). Claimed tow capacity 3100 kg (6830 lb). Unladen weight 1955 kg (4310 lb). The payload is 945 kg (2080 lb). If towing 3100 kg (6835 lb) that, plus the ute’s unladen weight is 5055 kg (11,150 lb). This leaves a payload of 830 kg (1830 lb) when towing 3500 kg (7700 lb). It is 2785 kg (6140 lb) towing 3100 kg (6835 lb). Still undesirable but not as bad as above.
Few utes remain ‘standard’
That typical 250-440 kg (550-970 lb) payload may just suffice for a driver, passengers, plus fuel. Few dual-cab utes, however, remain standard. Many will have a winch (40-50 kg [88-110 lb]). A bull bar (4-45 kg [8.8-99 lb).
More realistic towing capacity for dual-cab ute towing capacity is 2500 kg (5500 lb).
TV interference from LEDs – here’s what causes it
by Collyn Rivers
TV interference
TV interference from LEDs is an issue worldwide. It is mostly caused by LEDs in the same home (or RV) as the TV. This can be checked by turning them off. Another indicator of TV interference from LEDs is good daytime reception until lights are turned on. In the worst cases, TV reception is unwatchable, or not even obtainable.
TV interference from LEDs typically looks like this. It can also prevent a picture appearing.
TV interference from LEDs is electromagnetic ‘noise’ – known as Radio Frequency Interference (RFI). It is an unwanted by-product of some electrical devices. It has been a problem since the beginning of radio and TV. RFI has many sources. These include pollutants on power line insulators, electric fences, garage door openers etc. Most electrical stuff prone to generate RFI has protection to specifically reduce it. Or to shield its radiation. But not all have.
TV interference from LEDs – is from 2010 on
TV interference from LEDs escalated around 2010. Its cause was a global move to a cheaper way of powering low voltage dc LEDs from 110/230 volts. The new way includes switching the current on and off at very high frequency. In so doing, however, it generates high-energy electrical noise (RFI). Good quality LEDS have filters that limit RFI to a few metres. Ultra-cheap ones, however, have inadequate or no filters. As a result, TV interference from poor quality LEDs is a global problem.
Ongoing forum reports of LEDs ‘sucking up TV signals to drive the LEDs’ are fantasy. Nor can this form of RFI affect signal strength. It does however degrade sound and/or picture quality. In extreme cases it precludes reception altogether.
The TV interference from LEDs problem
Not all antenna installers are aware that poor quality LEDs can cause this problem. They may try to fix it by installing a new antenna. Doing this helps if the TV signal strength is too low. It cannot, however, assist if an already strong TV signal contains RFI.
They may also suggest adding an antenna signal booster. This can assist – but may boost RFI as well.
Where the TV signal is already strong, re-aligning the antenna to point away from the source of LED radiation assists.
Self-caused TV interference
To check whether RFI is self-caused, turn off everything electrical except the TV. Then, progressively turn things back on to see if any item causes it. If it does, check a few times. The first may just be a coincidence.
If (in RVs etc) 110-230 volt power is via an inverter, that unit is often the cause. Check by seeing if RFI ceases when the TV is connected to a 230-volt grid supply.
If RFI is only night-time related, cheap LEDs are most likely the cause. One brand sold by a major Australian hardware chain is (allegedly) notorious for this. High-quality LEDs are not cheap, but this is the only simple solution. It can also be done by replacing the tiny associated converter by its transformer-type equivalent. This fixes the issue, but costs more than a few really good LEDS!
It can also be done by adding cheap ferrite cores but needs amateur radio or similar experience.
In essence, apart from a possible antenna issue, there is no realistically affordable way of removing/reducing RFI noise from the signal received. That TV interfering RFI must be eliminated at the source.
TV interference caused by others
Matters become complicated if the cause is not yours. A neighbour causing it may welcome a fix as affects them too. But if that neighbour refuses to act, there’s little one can do (apart from offering to pay all costs yourself).
TV interference from LEDs – mostly from ultra-cheap ones
LEDs most likely to cause problems are ultra-cheap imports.
Also an issue is ‘specials’ sold by hardware stores and on eBay. The only solution is to replace them with good quality units from a reputable local supplier.
Techo talk
The RFI is typically 30 MHz – 300 MHz (and sometimes higher).
Those most commonly offending are the cheap 12 and 24 volt MR16 (also known as GU5.3). These run from 230 volts via a tiny inbuilt or associated switch-mode power supply. Some low price 230 volt GU10, E27 and B22 units are also a problem.
Apart from TV, the so-called RFI may affect 87.5-108.0 MHz FM radio, particularly 174 -230 MHz Digital Audio Broadcasting.
About our books
This article is by RV Books founder Collyn Rivers. Collyn’s books cover all aspects of RV usage – including solar. They are the Caravan & Motorhome Book, the Camper Trailer Book, and Caravan & Motorhome Electrics. Solar That Really Works (is for RVs). Solar Success (is for homes and properties). For information about the author please click on Bio.
RV forum common sense – a rare commodity?
by Collyn Rivers
RV forum common sense
RV forum common sense can be fine but used about things technical it’s likely to be based on misleading opinions that contradict the basic laws of physics.
Engineering utilises long proven knowledge. This may be (for example) about voltage drop along an electric cable (Ohm’s Law). It may be about the deflection of a spring under load (Hooke’s Law). Or the forces exerted by a travel trailer yawing or pitching (Newton) etc. All are based on long proven work and often centuries of proven practice.
Some RVers and even travel trailer makers seem at times also to assume they are immune to such laws. A major example is friction sway control. It works well at low speed – but is close to useless at 100 km/h. Why? It’s truly basic. Frictional force remains constant. Sway forces, however increase with the square of the rig’s speed.
Where opinion may come in is (e.g.) the safety factor required. Here decisions may well be financial as well as engineering based. It arises, for example, with bridges.
RV forum common sense can often be fine. It works well too when camping. But rarely with technical issues. Here, financial (not engineering) issues may predominate.
While I was a motor industry research engineer (before safety became fashionable) minor engineering changes could substantially reduce brake fade. The management decision, however, was to keep braking performance as is but to reduce brake drum size to retain the existing braking performance. Engineers provided facts. The decision was based on marketing and accounting opinion.
Fridges
RV forum opinions can regress to absurdity. One post advised a fridge was not cooling adequately. It later disclosed the fridge drew 10 amps via 10 metres of 1.5 mm² cable. My response was that the fridge was losing over one volt along that cable. Further, it may not be the only problem. And that it could not work properly until all was fixed. This resulted in posts to the effect that my response was only an ‘opinion’. And that ‘Fred says it’s nonsense’ etc.
My post was not an opinion. The relationship between voltage, current and resistance has been known since 1827. I responded accordingly – mentioning Ohms Law. This literally resulted in ‘what would that fella Ohm know about it? I’m a plumber and I can tell you the real world’s different mate’!
An ongoing issue is travel trailer stability. Here, almost everything is known as factually. But many argue that, in their opinion, Australia’s now hundreds of roll-overs a year is still too low to matter. Matter to whom?
Travel trailer common sense
An often heard example of travel trailer ‘common sense’ is: ‘people need exercise to be healthy. ‘It’s just common sense that lead-acid batteries need exercise.’
Lead-acid battery reality is the opposite! Lead-acid battery heaven is a maintained full charge and no load. If kept as a lead-acid version of a Labrador, that battery may live twenty years. But who needs a pet battery?
Supply cables
It may seem travel trailer common sense to join power cables as long as the connectors are kept dry. It’s not. Nor is this an opinion.
Travel trailer ‘common sense’ assumes a long gone primary reliance on earthing. That still matters, but there is now a better way. It is to monitor current flow in the neutral and active conductors. If all is well that should be equal. If not, current can only be flowing to earth via an undesired path. That may be via Uncle Fred changing a live light globe and breaking its glass. The unit (and RCD) detects imbalance and cuts power to that circuit.
Circuit breakers that detect excess current must act within 0.4 seconds. A human heart usually withstands that, but not longer. A circuit breakers speed, however, relates to the current flowing. And that’s related to cable size and length.
Australian and New Zealand supply cables are now such that contact breakers cut current at that cable’s maximum current rating within 0.4 seconds. If you join cables together you extend that reaction time. For acceptable cable lengths see: Supply Cables for Travel trailers.
Raising electrical issues on RV forums usually results in: ‘I’ve been doing that for fifty years mate – the #@%^$ electricity regulators don’t know what they’re talking about.’ Others then reinforce such terminally silly (and dangerous) opinions. Time and again such threads are locked. Or deleted.
Gas safety
Here, some respondents ‘opinions’ if followed, would cause brain damage and even kill. See my Gas Risk in Travel trailers. That article is fully referenced from world authorities in this field. Despite that, it receives ‘it’s only their opinion’ responses.
It is hard for non-technical people to know who to believe in essentially technical matters. Some distrust of ‘learning’ (even if backed by ample practical experience).
Some claim that readers know who to believe. Forum after RV forum, however shows this is not so. An ongoing giveaway is misuse of technical units. If you see ‘kph’ instead of km/h, or battery capacity of 100 amps – instead of 100 amp hours (or 100 Ah), stop reading. Misuse of technical units is a sure giveaway.
Another relates to energy being changed from one form to another without incurring loss. This is even more so where energy gain is claimed. A classic example is the MPPT (Multiple Power Point Tracking) solar regulator. It is commonly claimed to increase solar input. It cannot do so – it reduces losses in the system (by a typical 10%-15%).
Another claim is that LiFePO4 batteries have zero charge/discharge loss. It’s small – but zero is impossible. In this universe at least. If unsure why – Google ‘entropy’.
Further reading
Resultant arguing (and abuse) puts technical respondents’ reputations at risk. Even more, can be a moderator who shuts down threads that retain seriously dangerous advice. Because of this, most technical people have ceased doing so. I post on a couple of RV forums, but primarily post (or update) related articles on this website.
About the author
Collyn Rivers is an ex-motor industry research engineer. He switched careers in mid-life to become a technical author and publisher. He also has extensive practical experience with RVs. (Bio). All of his books are written in plain English.
They include the Caravan & Motorhome Book, and Caravan & Motorhome Electrics. Solar That Really Works (for RVs) and Solar Success (for homes & properties).
Trailer Dynamics Simply Explained
by Collyn Rivers
Trailer Dynamics
That travel trailers roll-over yet most vehicles don’t show trailer dynamics is not understood or is ignored. Trailer dynamics simply explained tells why. The main cause is that hitch extending from the tow vehicle’s rear. It not only allows but causes both tow vehicle and travel trailer to sway (yaw). Worse – if one yaw’s clockwise it causes the other to sway anti-clockwise. The further the tow ball behind the tow vehicle’s rear axle, the greater that effect.
As a travel trailer sways, the tow vehicle is caused (by that hitch) to yaw in the opposite direction. Pic: copyright 2014 https://solbsau.centrails.com
At low levels, this yaw usually dies out after two or three swings. It’s annoying but harmless. With some rigs, however, it may build up more and more. If this happens above a critical speed (specific to each rig) it may result in jack-knifing, and furthermore – a roll-over. In 2018 one of Australia’s five travel trailer insurers (alone) reported over 135.
A sad ending. Pic: source unknown.)
Why Caravans Roll Over
This problem, and its main cause, was first known in 1914. Trucks back towed overhung hitched trailers – that subsequently rolled over. The cause (that overhung hitch) was quickly recognised. By 1920 most commercial trailers had the hitch directly over the tow vehicle’s rear axle/s. Most still do.
With no overhang, the trailer pivots around its hitch. It barely affects the tow vehicle. Pic: copyright https://solbsau.centrails.com.
Early (about 1917) fifth-wheeler Adams Motor Bungalow. Pic: Glenn H Curtiss Museum (USA).
The inherently more stable fifth-wheeler travel trailers stem from this era (1912-1920).
As travel trailers yawed (and worse), people devised ways of preventing it. But they did not address the known causes. On the contrary – they invented various (patentable) add-ons intended to dampen yaw. Still used to this day, they reduce low-speed discomfort. They cannot, however, cope with major yaw forces that may result in rollovers. This is particularly with mainly long and heavy travel trailers. The reason is that most are frictional devices. Whilst effective at low speeds, the friction remains constant. Sway forces, however, increase with the of rigs speed. At 100 km/h, friction sway devices are only about 1% effective.
Europe’s travel trailer makers accept the causes: they keep travel trailer weight low. Their towing laws ensure travel trailers are about 20% lighter than whatever tows them. Safety is further helped by the general EU 80 km/h towing limit.
The Australian and US approach retain those add-ons, plus a so-called Weight Distributing Hitch. There are also effective electronic stability aids.
Mass, weight and inertia
For an explanation of trailer dynamics, a few technical terms have to be used. The major ones are weight and mass.
Whilst not an issue with things like cooking, weight and mass are different. With travel trailers and their tow vehicles, that difference is vital.
Mass is a measure of the amount of material in something. It remains exactly the same no matter where it is (including in space).
Weight is the effect gravity has on mass whilst on Earth. It pulls mass downward and that force is regarded and measured as ‘weight’. A given mass actually weighs less on a mountain top.
In space, a mass that weighs 10 kg (22 lb) on Earth has no weight. But if thrown that mass acts as if on Earth. It weighs nothing. But its thrown mass is still equivalent to a 10 kg (22 lb) weight.
For weighing stationary travel trailers and tow vehicles, mass and weight are the same. But once moving, mass attempts to follow a straight line. This only changes when an equal and opposite force deflects, slows or stops it. This effect is called inertia. (As with politicians, inertia resists change.)
Tow ball mass
Like thrown billiard cues, to keep straight travel trailers must be front-heavy. Travel trailer makers and owners have long seen about 10% of the travel trailer weight is sufficient. In reality, however, short centre-heavy travel trailers are fine with less. At a typical four metres or so, camper trailers’ tow ball weights vary from 3%-22.5%. It is rare to find one that is unstable.
Many travel trailer makers, however, now quote tow ball weight as that unladen. And with water tanks empty. Few now recommend laden nose weight, possibly because 10% can no longer be borne by many current tow vehicles. And the trend is to yet less.
Pic: https://solbsau.centrails.com
As with a see-saw, the effect of weight depends on where it is relative to its pivot (here the axle). A, B and C (plus and minus) are all one metre apart. +D is half a metre from +C. A weight of 100 kg (220 lb) at +C and -C has an ‘effective weight’ (mass) twice that at +/-B. At +D it is two and a half times that at +B.
The above is a very short (4.0 metre/13 foot) travel trailer. Were it 7.5 metres the effect of weight (mass) at the tow ball is about 300 kg (660 lb) for every 100 kg (220 lb) there. Despite that many travel trailers have twin gas cylinders and batteries so located. Plus two spare wheels and even a tool-box at the far rear.
The effect of mass and where it is located matters when a travel trailer pitches or yaws. The weights’ forces (mass) then increase not only by their distance from the axle/s. They increase while pitching and/or yawing.
The effect of weight along the length of a travel trailer. Concept and Pic: rvbooks.com.au
With the weight central the bar swings and stops with ease. Moving that same weight outward the bar causes the bar to be increasingly hard to swing. And to stop swinging. The same thing happens if you simulate pitching. Also, the faster you move the bar, the harder it becomes. Travel trailers behave like this!
Weight distributing hitches
tow ball weight on an overhung hitch acts like pushing down handles of a wheel-barrow. It causes the front to lift, thus reducing weight on its front tyre/s.
On a tow vehicle, the front wheels need to steer, such weight loss needs rectifying. The WDH (weight distribution hitch) used on large travel trailers levers up the rear of the tow vehicle. By using the tow vehicle’s rear axle and wheels as a pivot, the WDH levers the front wheels down.
Whilst partially remedying one problem, the WDH, however, introduces another. It cannot reduce the yaw forces caused by that tow ball mass on an overhung hitch. Front end weight is partially restored, but the WDH inherently reduces the tow vehicle’s straight line and cornering ability by about 25%. It also rapidly and cyclically changes front/rear footprint grip when a travel trailer pitches. If yawing at the time this can escalate and cause the rig to jack-knife.
The purpose of a WDH is to reduce the effect of hitch overhang. This hitch undesirably extends it. Pic: Original source unknown.
A WDH is like a truss used to support a hernia. It’s better to remove that hernia (the ‘need’ for that truss). Reducing travel trailer end-weight is a far better way. It has long been the major European approach. There, travel trailers are typically 1200-1600 kg (2650-3525 lb), (about 60% of most local product). They are end light, enabling tow ball weight of only 60-80 kg (130-175 lb). They have no need for a WDH. Nor do they have provision for one. There are long such travel trailers and similarly lighter per metre than the current local product. They are typically towed by cars (less so by 4WDs).
Right now, a WDH is necessary with end-heavy travel trailers over (say) 5.5 metres (18 ft), and a laden weight of 1800 kg (4000 lb). A saner approach is to design, scale and load travel trailers so no WDH is required.
Trailer dynamics – yawing
A long front-heavy travel trailer resists changing direction. This causes it to feel ultra-stable whilst moving in a straight line. This usefully resists wind gusts, and changes in road camber etc.
A major downside that the so-called inertia that normally keeps that ultra-stable becomes its very undoing. It may overwhelm the tow vehicle’s ability to make an emergency turn. As with a big container ship, it resists moving other than straight ahead. But a major disturbance (like a ‘perfect storm’ wave can (and sometimes does) roll one over.
Travel trailers of similar length and weight, but different mass distribution, have very different yaw inertia. An end-heavy travel trailer has far more yaw inertia than a similar length travel trailer with centralised mass.
Optimum tow ball mass
Those working in this ongoing field of research, backed up by real-life testing agree that optimum tow ball mass (for local product) is 8% to 12%. It is 6%-8% for typical EU product.
In practice, many travel trailer makers ignore this. Many quote only the unladen tow ball mass. One, of plus 2.5 tonnes unladen is under 4.0%.
This 5.3 metre Phoenix (of the 1990s) has the axles set well back. Note the truss-braced chassis. Pic: Barry Davidson.
Good trailer dynamics necessitate mass centralised (as far as possible) over the travel trailer‘s axle/s. It also requires the axle/s to be set toward the rear (as with the Phoenix above). This is aided by keeping end weight ultra-light. It necessitates using light composite materials.
Excess yaw inertia is a bigger problem than excess travel trailer weight as such. It is becoming increasingly necessary as available tow vehicles are increasingly lighter and, furthermore, less able to support high tow ball mass.
Trailer dynamics – sway (yaw) limiters
Particularly with low tow ball loading, a travel trailer is likely to yaw slightly at low speed. This is annoying but harmless providing it ceases of its own accord within two or three such cycles. Sway (yaw) limiters may dampen it to almost zero. They are often included on new EU travel trailers.
There are two main types. Firstly, friction mechanisms dissipate yaw energy as heat. Secondly sprung cams (or similar) that ‘lock’ travel trailer and tow vehicle in a straight line. The rig then normally corners by distorting by tyres’ footprints. The cams release only when turning sharply.
While reasonably effective at low/medium speed, all such add-ons are less so at speed. Further, when a sprung cam’s limitations are exceeded it suddenly releases unwanted energy into an already dangerous situation. (It seems akin to having a King Brown as a guard-snake).
The major potential problem, however, is that all such devices mask serious inherent instability.
This Reese dual-cam sway control ‘locks’ the travel trailer to the tow vehicle. It releases only on sharp turns and high-level yaw.
Electronic sway control
Some 4WDs have so-called inbuilt ‘sway correction’. It automatically and asymmetrically brakes the tow vehicle (left/right) to partially counteract trailer’s sway. The X3 BMW can interlink this to a towed vehicle.
AL-KO’s ESC (Electronic Sway Control) detects and attempts to correct travel trailer yawing by travel trailer braking. It is a ‘detected emergency’ system’ that actuates only if the travel trailer exceeds a lateral acceleration. Or 0.4 g or four repeated successions exceeding 0.2 g. That 0.4 g is the very highest cornering force sustainable with a truly stable rig. It cannot be achieved if a WDH is in use. The limit then is about 0.3 g.
How the AL-KO ESC works. Pic: AL-KO Europe
The effect is akin to a cyclone suddenly encountering cooler water – it loses its energy source. The AL-KO ESC does not correct yawing at less than dangerous levels. Forum reports that ‘my travel trailer became more stable at all speeds once the AL-KO unit was fitted’ are thus nonsensical.
The AL-KO unit can be retrofitted to trailers that have AL-KO brakes. It has proven effective in Europe, but it’s unclear if it copes with a long end-heavy travel trailer yawing strongly at high speed. It is generally similar to the IDC system from Germany.
The Tuson/Dexter DSC system (USA) applies braking asymmetrically (i.e. out-of phase with the yaw). It detects yaw in a different manner and acts at lower levels.
As noted above, any ‘sway correcting’ system may mask underlying instability. Their makers advise they must not be used to correct existing instability. Furthermore, they cannot overcome the laws of physics.
Weight of tow vehicle
Ideally, the laden travel trailer should weigh no more than about 80% of that of the laden tow vehicle (and that is typical in the UK and EU where the towing speed limit is 80 km/h).
There is currently a major issue with some dual-cab utes, that whilst rated at 3500 kg (7715 lb) tow capacity, they can only do so if that ute is semi-laden. This can lead to a 3500 kg (7715 lb) travel trailer being towed by a 2500 kg (5500 lb) tow vehicle. See: claims-for-dual-cab-ute-towing-capacity-mislead/
Critical speed
Every travel trailer tow vehicle combination has a critical speed. If that is reached, and particularly if exceeded the rig may experience rapidly escalating up yaw that cannot be corrected. The cause is complex – and explained in my article Travel trailer & Tow Vehicle Dynamics. It is described in detail in my book Why Caravans Roll Over – and how to prevent it.
Extensive test data suggest the critical speed for long end-heavy ‘vans may be too close to Australian speed limits for comfort (and some now probably under it). The towing speed limit in the UK and Europe is typically 80 km/h – despite generally more stable and weight balanced rigs.
No need for independent suspension
There is little or no need for independent suspension on trailers (it is far from common on 4WDs rear axles). It enables the 100 mm or so otherwise needed vertical travel space of a beam axle to be used for water storage etc. It has no other real benefit.
That independent suspension is wrongly seen as somehow ‘better’ is partly due to a lack of high-quality leaf spring suspension systems. Car suspension is designed around human physiological constraints.
These constraints do not apply to travel trailers. As AL-KO proves worldwide there is not the slightest need for long travel suspension for travel trailers.
If building one’s own, use the rear springs and shock absorbers of a post-2006 Hilux.
If independent suspension has to be used, check out the twin beam axles (used by Track Trailer and Vista).
Tyre behaviour
Pneumatic tyres do not behave as do solid tyres. Their behaviour can be simulated by holding an inflated balloon firmly by its sides and pressed it onto a hard surface. Rotating its sides slightly causes the balloon to distort and apply, via its side-walls, a force across its elastic surface footprint.
Were the balloon a steered wheel, the revolving distorted footprint would cause the vehicle to turn in a radius that is less than that of the distorted footprint. This difference is generally known (but misleadingly) as the slip angle.
The slip angle concept.
Unlike friction generally, a pneumatic tyre’s cornering power is not proportional to its loading. (It’s about 0.8 of it.) This causes major issues when a vehicle is pitching and/or yawing. Slip angles vary accordingly. Pitching and yawing primarily affects the tow vehicle’s rear tyres. It introduces high-speed steering irregularities. Beyond a certain point, all grip is lost and the tyre/s slide out of control.
Tow vehicles
The greater the weight of the tow vehicle, relative to the travel trailer, the better. This is becoming a major issue as tow vehicles become increasingly lighter. The laden tow vehicle should be at least as heavy as the laden travel trailer, ideally 30% or greater.
Also important is the minimal distance from the centre line of tow vehicle rear axle to tow ball. The average (in Australia) is 1.24 metre from tow ball to centre line of the tow vehicle’s rear axle.
The tow hitch itself should have a minimum length: some extend by unnecessarily and undesirably. The further the tow ball is behind the vehicle’s axle, the greater the extent and severity of snaking. This also reduces the critical speed where chaotic behaviour may (not necessary will) be triggered. Many travel trailer accidents involved semi-laden dual cab tow vehicles with extensive rear overhang.
Speed
This is a vital factor. The higher a travel trailer‘s inertia, the lower the critical speed. That critical speed may well be below the legal limit for high yaw inertia travel trailers. Or too close to it for comfort. Ideally, keep the speed below 100 km/h (80 km/h is strongly recommended for long end-heavy travel trailers).
This problem mostly affects end-heavy travel trailers, particularly long ones. It can also affect shorter travel trailers towed at speed on motorways. Light travel trailers (sanely laden) up to a probable five metres are at less risk, particularly if there is a centre kitchen.
Owner actions
Load travel trailers such that anything heavy is above or as close to the axle/s as possible. Do not have washing machines, heavy toolboxes, spare wheels etc at the extreme rear.
Minor yawing at low speed should die of its own accord. If however, yaw begins at above the critical speed, it is rarely recoverable by driver action. This is because any steering ‘correction’ tends to increase the disturbing forces.
Trailer dynamics – conclusions
Vehicle stability was well understood by the late 1930s, and refined thereon. Most work on trailer dynamics began in the late 1970s. There are many published papers (backed up by practical real-life testing) but hard to follow without a background in this area. The main leader is the UK’s University of Bath (financed by Bailey Travel trailers).
Further information
A major bibliography is included in my major Travel trailer & Tow Vehicle Dynamics.
For a UK-oriented view see the (very readable) Understanding the Dynamics of Towing, by Simon P Barlow.
If you find this article of value or interest please buy one or more of our books. Caravan & Motorhome Book, the Camper Trailer Book, Caravan & Motorhome Electrics, Solar That Really Works (for cabins and RVs) and Solar Success (for home and property systems). For author information Click on Bio.
This topic often arises on RV forums. If you feel it may assist others please consider placing this Link on the appropriate forum thread.
This article and associated drawings are copyright RV Books, Mitchells Island, NSW 2430 (Australia). They may not be copied nor reproduced in any manner, nor changed in any way or form, without the Express Written Permission of the copyright holder.
All solar house – self-building an off-grid all solar house
by Collyn Rivers
All Solar House
My wife and I self-built our all solar house in Australia’s far north in 2001. While we no longer live there, it is still (2020) beautiful and practicable. Living with solar alone is 100% possible. Here’s how and why.
The upper third of the 10-acre block. The solar array for our all solar house is bottom left of the photograph. Pic: rvbooks.com.au
Apart from bore water, the 10 acres (of Cable Beach frontage) had no services. Using hi-tech materials and techniques, however, enabled me and my wife to self-build a beautiful and totally practicable living space. Plus extensive irrigation.
The land at Ngungnunkurukan (known as Coconut Well), is 21 kilometres north of Broome – one of the world’s most isolated towns. Broome’s nearest city is in Indonesia. It nearest in Australia (Darwin and Perth), are both over 2000 km away. The 12,000 or so population is over 50% indigenous.
The land directly adjoins the route of one of three major Aboriginal songlines traversing Australia. Moreover, it also has major rock formations significant to the local Yarwu community.
Original bush and sand dunes front directly onto a tidal lagoon. Furthermore, the Indian Ocean is a mere 400 metres away.
Protecting the culture
Knowing the significance, we followed the traditional owners’ wish to protect rocks and significant trees. And, at the same time, to restrict access to a sacred part of the site. That part was welcomed! It’s a breeding area for King Brown snakes.
We attempted, also, to avoid heavy earth-moving machinery being close to that area. In addition, Broome Shire and the local fire authority allowed obligatory fire trails to detour around such areas.
Cyclone Rosita
We moved onto the land in April 2000. Cyclone Rosita struck ten days later. We buried our ultra-strong OKA off-road truck to its chassis and also strapped a table across its windscreen. This gave shelter against the subsequent 180 km/h plus wind.
Whilst scary, that cyclonic wind caused us to upgrade the engineering. Furthermore, we added a virtually indestructible cyclone shelter. It’s rarely needed but provides visitors with a truly strong bedroom.
All solar house – our main requirements
Our main requirements were light and space. And visually, to link the ocean in front to the virgin bush at sides and rear. The original concept was good. Nevertheless, as an engineer myself, it was clear the designer’s structure was far from adequate. It was subsequently and brilliantly re-designed by Garry Bartlett of B&J Building Consultants (in Broome). B&J also fabricated the massive steel mainframe.
Despite its complexity, the all-steel framework was erected in one (12 hours) day. The diagonal steel tubes add strength. They also double as water drainage for the gutters. The Pindan soil really is this colour. Pic: rvbooks.com.au
Bridge-like construction
The house’s superstructure is closer to an arched steel bridge than a house. It’s structural engineering – not traditional building. It is almost entirely concrete, steel and glass. There is not a single mud-brick, straw bale, or any but non-structural timber in it!
The main area – looking north. Pic: rvbooks.com.au
It is also rare in having a ceiling 4.3 metres high at its centre. Apart from its roof, the exterior is almost entirely cyclone-proof toughened glass sliding doors. Each has slide-open stainless steel security mesh. There are no full-height internal walls, only a couple of 2.0 metre (6 foot) high partitions.
Double curvature roof
The all solar house’s main strength is its double curvature roof! This is fabricated from heavy gauge Colorbond steel. It is secured by 14 gauge Tek screws. In addition, it has cyclone washers at every channel. Furthermore, the purlins are welded to massive curved RSJs (rolled steel joists). A similar Colorbond ceiling likewise attaches directly to the purlins’ undersides. The whole forms an immensely strong, but nevertheless light, beam.
The roof is tied down by forty steel posts. Each is 100 by 100 mm square. The posts are bolted to a 600 by 600 mm reinforced concrete perimeter beam. Diagonally located 150 mm diameter (and 20 mm thick) steel tubes provide further support. They also double as rainwater down-pipes.
The RSJs sections (each over 2000 kg [4400 lb]) were rolled to the desired double curvature in Perth. They were then trucked the 2100 km to Broome and welded into complete sections. Then trucked 4200 km to Perth and back for galvanising. Roofing sections were rolled to the same curvature.
Precision construction
The all-steel structure demanded tolerances of only a few millimetres. This is closer to watch-making than builders’ typical plus or minus a centimetre. Or three. The 400 mm perimeter (40) beam’s needed placing within two to three millimetres. Surprisingly, it worked. Furthermore, the 150 m² structure is within five mm² across diagonals.
Building the all solar house
When it came actually building, we found that no local builders were willing to assist. They seemingly felt it was closer to bridge-building than house building. This was not, however, a major problem. I (Collyn) was originally an engineer. My now-psychologist wife (Maarit) acquired welding and production-engineering certificates at Broome TAFE. She also (and usefully) became a certified venomous snake handler.
We had contractors pour the 300 mm thick concrete floor. B&J assembled the huge steel frame – assisted by a 200-tonne crane. Even at that capacity the crane consequently worked hard. It had to position the massive steel beams at its full extension of over 40 metres away. We had contractors install the Colorbond roof and ceiling. Likewise, internal plumbing and 230-volt ac wiring.
To enable mainly solar to power even the construction, I arranged that first. I designed an initial 2000 watt system that I located on the roof of an existing shed. It had about 45 kilowatts of battery storage and an inverter that could cope with an 11-kilowatt peak draw. The array was later expanded and moved closer. It still (2020) provides a reliable 3.4 kW – and about 18 kWh/day most year-round.
Building started building in earnest in August 2000. We moved into the (semi-completed) but already all solar house by Christmas.
There are no full-height internal walls. The floor is ochre-coloured polished concrete. Pic: rvbooks.com.au
Powering the all solar house
The main solar array. A further bank (of six modules) was added just after this 2005 pic was taken. Pic: copyright rvbooks.com.au
The solar system initially puzzled contractors. They knew the closest power lines were 20 km away. But here was 230 volts at considerable wattage. It was initially hard to persuade them it was from solar.
This SAE 11 kW surge inverter installed in 2001 works well to this day. Pic: rvbooks.com.au
The original batteries were flogged to death by a caretaker. They were consequently replaced by sixteen 12-volt gel cell batteries. Each was 235 amp-hour. An 80 amp Outback Power regulator controls charging.
Sixteen 12-volt (235 amp-hour) gel-cell batteries were connected in series-parallel. They provide 940 amp-hours (45 kWh). Pic: rvbooks.com.au
Naturally cooled
Indian-ocean cooled air is drawn into the house via its usually open but fly-screened doors. The air is subsequently extracted via roof vents. Air-conditioning was deemed unnecessary. A cool ocean breeze usually develops by midday year-around.
A very efficient Fisher & Paykel fridge copes well. Cooking is via LP gas (using 40-litre cylinders). Water heating is solar only. It even works well in winter.
As LEDs were not available back then, lighting was all via compact fluorescents. Ample power was available to drive them. Had we built later, however, we would have used LEDs throughout the property.
Water
Despite excellent bore water, the house uses rainwater – even for toilet flushing. The 280 square metre roof has two deep and wide stainless steel gutters. These are inset between the roof and the ceiling for cyclone protection. Water flows via diagonal bracing tubes to sunken 200 mm pipes. These fill a 14,250-litre holding tank that captures torrential seasonal rain. The fall is so heavy the tank fills inside an hour. The water is then pumped to the main 100,000-litre tank.
Water is supplied to the house by a pressure pump and 500-litre water pressure tank. The pump replenishes the pressure tank once or twice daily. It is silent and efficient, moreover running only twice a day for a few minutes each time.
Swimming pool for an all solar house
Quotes for the pool’s circulation system were around $60,000. Finding them based on traditional technology, we designed and built our own. It cost a mere $7500 (in 2002.) This, as with all the house and property, runs from solar alone.
Lorentz Badu pump after seven years. It runs on 40 volts dc and pumps about 35,000 litres a day using four dedicated 120 watt solar modules. (The apparent rust is the Kimberley’s Pindan sand that stains everything it touches.
Lorentz Badu pump after seven years. It runs on 40 volts dc, pumping about 35,000 litres a day from four 120 watt solar modules. (The apparent rust is the Kimberley’s Pindan sand. It stains everything it touches).
A 480-watt solar array directly drives a Lorentz 48-volt brush-less DC motor pump. No batteries are needed. The pump accepts a wide range of voltage, so no solar regulator is needed. As a result, water circulates all day under the Kimberley’s typical all-day sun.
No chloride is used. Irrigation water first passes through the pool. It effectively replaces about 10% each day.
Crystal clear water. A 48-volt dc pump is powered by the four 120 watt solar modules seen here. It runs all-day. The house’s inset gutters can be seen here. The protruding section (left) is an ultra-strong cyclone shelter. (Full details of this pool are in Solar Success.)
Crystal-clear water
The crystal-clear bore water is among the world’s purest. It comes from the King Leopold Ranges – 700 km north-west. The land in between is totally untouched. We used only 2% of our allocation, 98% consequently pours into the ocean.
Sewerage is septic. We would have preferred a more ecologically viable system but, notwithstanding, Shire regulations prevented it.
Broome Shire otherwise cooperated totally. It rejected the original plans as cyclone protection was inadequate. But that confirmation was nevertheless welcome. I’d calculated that too. The upgraded specifications were done by the then-mayor – he was a structural engineer.
Not all worked as hope. One downside, for example, was the kitchen. Built locally, it’s very poorly made. ‘Call yourself a cabinet maker’, said Maarit to one. ‘You’re not even a half-competent bush carpenter.’
My Finnish wife Maarit – in blacksmith mode. Pic: Broome TAFE
A time to move
The all-solar house worked well for us for ten years. Whilst there I wrote and successfully published five books. I also spent four years at Broome’s tiny university campus, auditing the Aboriginal Studies course. Meanwhile, Maarit acquired two more university degrees. She subsequently obtained her Master’s degree.
We later needed to be closer to our rapidly expanding Sydney family. Reluctantly, we sold the property in 2010. A visit in 2019 however, showed that, apart from new batteries, all still worked well.
Our home (in Church Point) has subsequently become an all solar house too. It has a 6.4 kW system with Tesla 14 kWh battery back-up. On most days it produces far more than we use. The surplus is fed into the grid under a two-year contract at 20 cents per kW/h.
A 6.4 kW solar system supplies all the three-story home’s needs plus. Pic: rvbooks.com.au
Further details
Fuller details of the Broome’s solar, swimming pool, water pumping are in my book Solar Success.
It is totally feasible to build an all solar house. That book shows specifically in detail how to get it right first time.
Solar That Really Works specifically cover cabins and all RVs. Caravan & Motorhome Electrics specifically covers this. Caravan & Motorhome Book gained excellent reviews. To quote Caravan World: ‘Collyn Rivers has put his encyclopedic knowledge into print . . . there is virtually no issue he hasn’t covered.’
Click here for a full index of my articles in this and other areas. Bio.
Is Travel trailer Independent Suspension Essential? – the answer is no.
by Collyn Rivers
Is Travel trailer Independent Suspension Necessary?
Is Travel trailer Independent Suspension Necessary? Or is a marketing issue? It is not an engineering issue. As this article explains, travel trailer beam axles are generally better.
Until 1930 or so most cars had beam axles (typically leaf sprung). A US-led wish for softer suspension, however, caused an unexpected effect.
As one or other wheel of a softly sprung beam front axle rises or falls over undulations it causes the often fast-spinning wheel to rise and fall in an arc. That wheel acts as does a gyroscope. It attempts to swing sideways. As the front wheels are connected by a horizontal track rod, if one rises in an arc it causes the other turn likewise. If not adequately dampened, this so-called gyroscopic precession builds up alarmingly. The front wheels swing violently from lock to lock. They also tramp up and down. This is related to speed – and became increasingly serious as cars became faster.
It was realised that this issue is inherent with beam axle located steered wheels. It was also realised that it can only be fully overcome by having the wheels rise and fall vertically. And independently. US engineers seemed unaware that Lancia had been using independent front suspension for a long time. A few other had too: Lanchester around 1900, and Morgan a year or two later.
As with a travel trailer‘s, beam axled car rear wheels are subject to similar forces. As they are not free to swivel, however, there are no unwanted effects. Hence many to this day (particularly 4WDs) retain beam rear axles.
Is Travel trailer Independent Suspension Necessary
Travel trailer Independent suspension. Pic. Jayco.
For reasons that relate mostly to marketing, Australian RVers are led to believe that travel trailer independent suspension is essential. The opposite is closer to reality. For travel trailers the type mostly used (trailing or leading arms) has a major downside.
Conventional travel trailers are towed by a centrally-mounted hitch that is about 400 mm above ground. When one travel trailer wheel traverses a bump (or depression) the front of the travel trailer rocks around that hitch. The travel trailer‘s springs may deflect – but not by much. This is readily seen by looking in the rear-view mirror as a travel trailer crosses rough going.
Effect on the centre of gravity
The major issue now is that the centre of gravity is at much the same height as with as a beam-axled travel trailer. That trailing arm suspension, however, introduces a considerable lever effect (Moment Arm) adding to that sway. This effect is even more so at the extreme rear. A pair of high slung spare wheels weighing (say) 80 kg (175 lb) has an effective mass of many times that weight. (The effect when swaying is not unlike a camel bending both legs on the same side.)
Further, a travel trailer with trailing arm suspension does not roll as such. It rolls around a diagonal axis that is at tow ball level (and centred) at the very front that causes it to sway around the ground level at its wheels. The centrally located hitch also causes it to adopt a duck-like waggle as it sways.
Because of this effect side forces cause a trailing arm suspended travel trailer to sway to a far greater extent. This may not be noticed in normal driving but becomes only too apparent in excess cornering speed, an emergency swerve, or air pressure forces from a passing truck.
Apart from trivial tyre depression a beam axle travel trailer‘s chassis always remains vertical to the surface. When a side force is applied the sprung mass rolls around an axis that is about the same height as the tow ball. There is thus very little lever effect (Moment Arm) to increase the effect of roll forces.
The Al-KO trailing arm suspension introduces a similar effect but as it has far less movement the sway is minimised. Such sway can be avoided by using the horizontal arms (as on the front of most cars) – or by using two pivoted full-width beams as in the Track Trailer TVan. But all take up needed central space.
The ideal suspension
The ideal beam axle travel trailer suspension needs to be similar in concept to that of the front of the superb 4.2 litre TD Nissan Patrol: a few DIY camper trailers actually use that (with a light beam axle). It is essentially a properly located hollow section (or I beam) axle with well-damped coil springs or airbags.
Sadly, however, little work is done in Australia to develop properly engineered beam axle suspension. Most use far too short stiff leaf springs intended mainly for garden trailers. There is one exception but its spring leaves are really too short for travel trailer use.
As a result, many locally-made travel trailers have soft long-travel suspension that mainly deflects when least needed i.e. whilst swaying. Many have dual shock absorbers per wheel – yet towed by 4WDs that cope adequately with only one per wheel.
Building your own ideal suspension
The simplest way is to use the rear leaf springs from a Nissan Patrol or Hilux, minus a leaf or two, and a proprietary hollow section steel beam axle (or I beam). Use also the associated shock absorbers. The spring deflection should be such that (prior to the shock absorbers being fitted) the laden travel trailer should bounce on its springs at about twice a second. Given the correct weight distribution etc. you will find it tows like a dream.
My Caravan & Motorhome Book goes into this at greater depth.
If you find this of interest please Link to it on appropriate forums – and do please tell your friends to read it.
Caravan fridge problems – how to fix the most common faults
by Collyn Rivers
Travel Trailer Fridge Problems
Travel trailer fridge problems are due to poor ventilation, inadequate cable size and/or insufficient power to drive them. Here’s how to fix them.
Pic: Original source currently unknown.
Q. My travel trailer fridge works fine whilst on 230 volts, but not on 12 volts when we free camp. How can I can tell for sure if the fridge is faulty?
A. You can be 100% sure if you remove the fridge. Then see how it performs standing alone in a garage at much the same temperature.
Poor installation
Q. A friend says you emphasise in your book (Caravan & Motorhome Electrics that most travel trailer fridge problems are due to faulty installation. How has this come about?
A: A probable 95% of travel trailer fridge problems are because they are poorly installed. There are two main types of travel trailer motorhome fridges: 12/230 volt compressor, and 12/230 volt/ LP gas (so-called) ‘three-way’ fridges. Both suffer from poor installation. Some RV makers and many self installers do not understand how fridges actually work.
Fridges do not make cold. They are simply pumps that moves heat from where it is not wanted – to where it does not matter. You must have a cool air inlet at their base. You also need to direct that cool air through the fridges cooling fins. Rising hot air must easily exit.
Ventilation is vital
Ventilation is totally vital for three-way fridges. This only too often insufficient. Some have none at all. Unless ventilation is provided as specified (and illustrated in Caravan & Motorhome Electrics) they have no chance of working correctly, on either electricity or gas. See below if the fridge works on gas and 230 volts, but not 12 volts.
Many travel trailers now have access to 230 volts, so they use this most of the time. Here, cable size can usually be relied on to be fine. Use much heavier cable if it runs on 12 volt solar/battery power. The required cable, however, is costly – so is rarely used. Current draw on 12 volts is very high. It is only feasible from a vehicle alternator, and short lunchtime stops from battery power.
Q. I know travel trailer fridge 12 volt fridge cable is usually too small. How heavy must it be?
A: This depends on the distance from the battery – it should not exceed two to three metres. Errors are caused by there being several ways of specifying cable size.
When specifying cable size, makers of electrical stuff either quote the cross-sectional area in square millimetres, in AWG or B&S. The latter are identical for all practical purposes. For most electric compressor fridges, the minimum is 4 mm² (AWG 10), but 6 mm² ( AWG 8) is preferable. Three-way fridges draw from 12-30 amps. These really need 8 mm² (AWG 7) unless the distance is less than two metres (when 6 mm² is fine).
Auto cable size
Q. I hear there is a problem with the auto cable sold in auto parts and hardware stores.
A. Auto cable is usually just fine. But, for reasons that defy sanity, auto cable makers use similar ‘numbers’ as above (e.g., 4 mm, 6 mm) to imply something totally different.
Auto cable ‘4 mm’ is not 4.0 mm² – it is the overall diameter of the cable including its insulation. That rating is the size hole you can push the cable through!
Worse, auto cable insulation thickness and type varies from maker to maker. Most 4 mm auto cable is anywhere from 1.8 mm²-2.0 mm². Most 6 mm auto cable is 4.6 mm². The reason why so many fridges are affected is because that 4 mm² and 6 mm² cable are the sizes most commonly specified. Be aware that even if you ask for (say) 4 mm² cable what you almost always sold is 1.8-2.0 mm² auto cable. Many people fall into this trap as few vendors know there’s a difference. (The square mm size is, however, usually shown in the cable’s specification.)
Travel trailer fridge – current ratings
Q. My three-way travel trailer fridge draws 25 amps. It is connected to the tow vehicle battery by ten metres (total for twin conductor) of 35 amp cable – yet barely works. A friend has your Caravan & Motorhome Book (that has a lot about travel trailer fridge problems). He says the cable is much too small. How can this possibly be? It’s already three and a half times the necessary current rating!
A. Current ‘rating’ is mostly misunderstood. It is not a current carrying recommendation but a fire rating that relates only to the current the cable can carry before its insulation begins to melt. The rating has absolutely nothing to with voltage drop. The most commonly used ’35-amp’ cable can be as small as 4 mm auto cable (1.8 mm²)! Ten metres of this introduces a massive three volts drop. That fridge will barely work at all. The minimum you need is 10 mm², over seven times the size.
You need to locate that battery in the travel trailer, charged from the alternator by a caravan-located dc-dc charger. See: dc-dc charging. Still use proper size cable. (You owe your friend, and that fridge, one considerable apology!)
About the author
Collyn Rivers is an ex motor industry research engineer who switched careers in mid-life to write and publish technically correct books in plain English. They cover the travel trailer, motorhome and solar areas.
The ‘overall’ ones are the Caravan & Motorhome Book, and the second edition Camper Trailer Book. Electrical issues are covered in Caravan & Motorhome Electrics, solar in Solar That Really Works (for cabins and RVs) and Solar Success (for home and property systems).
Travel trailer wheel placement
by Collyn Rivers
Travel trailer wheel placement
Travel trailer wheel placement is a vital issue affecting on-road stability. This article explains why, and the position along the chassis with which they should best be located.
A conventional travel trailer is always a compromise. This is because it is towed via hitch at some distance behind the tow vehicle’s rear wheels. If that vehicle sways clockwise, that hitch overhang causes (not just permits) the travel trailer to sway anti-clockwise. If the travel trailer sways clockwise, it causes the tow vehicle to sway anticlockwise. It is essentially an unstable concept, but safe within limits.
The major constraint of travel trailer wheel placement is the basic laws of physics. These include two major distances. One is the tow vehicle’s wheelbase (distance between the front and rear axle). The other is the travel trailer‘s so-called radius of gyration.
Travel trailer wheel placement – the radius of gyration
The radius of gyration is a distance. With a trailer, it is that distance from its tow hitch to that point along it was all its (laden) mass concentrated in one place. The greater distance the better. For optimal travel trailer wheel placement, the axle/s should be just behind that location.
As, like an arrow, to be stable when moving, a trailer must be nose heavy (here by about 8-10%). For ideal travel trailer wheel placement, they should be as far back as feasible. This is readily possible by centralising weight either side of those axles. Moreover, by minimising all other weight, particularly at its extreme rear.
Locating heavy spare wheels on a travel trailer‘s extreme rear indicates one of two things. Whoever designed does not under basic physics. Or does – but ignores it. And why two spare wheels – when the tow vehicle has one (and with some- just a repair kit and inflator).
Measuring the radius of gyration
This is readily done, but as far as is known, no travel trailer maker in Australia does so. That required is a frictionless turntable, the rotation of which is constrained by springs. The travel trailer is then centralised on that turntable and twisted by (say) 30 degrees and released. The time it takes to return to the starting position is a measure of that radius of gyration. The longer it takes, the greater that radius.
You can readily simulate travel trailer wheel placement by holding a bottle of wine in each fully extended hand – and twisting at varying speeds. (Either red or white is just fine).
Correct travel trailer wheel placement can also be done arithmetically. Like a loaf of sliced bread, the travel trailer is (theoretically) ‘sliced’ along its length. The ‘weight’ of each slice is then measured.
The tow vehicle’s radius of gyration is limited by the lateral distortion of its front and rear tyres. Moreover, also by how far they are apart. Here, the greater the better. Most vehicles used for towing (in Australia) are about three metres. In this respect, one of the best tow cars ever made is that least probable. It was the DS Citroen. It had virtually a wheel at each corner.
DS Citroen towing an Airstream Travel trailer – here again notice the ideal travel trailer wheel placement. Pic. source unknown
Only one local travel trailer maker appears to have realised the need for correct travel trailer wheel placement. He was Barry Davidson. He did so for his 1990s Phoenix range. They have a legendary reputation for excellent towing stability.
An example of the now-legendary Barry Davidson-designed late 1990s Phoenix. Note the ideal travel trailer wheel placement. Pic: Caboolture Travel trailers.
Inverters for travel trailers – and motor homes too
by Collyn Rivers
Inverters for travel trailers
Buying inverters for travel trailers can confuse. Prices vary for products that may seem identical but are not. Here’s what to buy.
Inverters vary in efficiency, ability to run any type of load, over-load capacity and safety. Modified square wave inverters are the cheapest but not all appliances will run from them. They can damage equipment such as laser printers. Sine-wave inverters run anything they are big enough to power. Unless you truly know what you are doing buy a sine wave unit. Good inverters for cost more, but they being efficient, they need less energy.
High-quality sine wave units are >90% efficient. They run equipment without risk of damage. Often called ‘pure’ sine wave inverters they introduce minor distortion, but too little to matter. The output is usually cleaner than mains power.
Inverters for travel trailers – transformer or switch-mode?
There are two main inverter technologies. One uses heavy iron-cored (doughnut-shaped) transformers. The other uses lighter and cheaper switch-mode technology. Each can be designed to produce modified square wave or sine wave output, but surge capacity is very different.
![Inverters for [cara_s] - and motor homes too - electric vehicle batteries,book on batteries,electric car batteries,lithium ion batteries for electric cars,electric car battery technology,how long do electric car batteries last,electric vehicle battery life](https://solbsau.centrails.com/wp-content/uploads/2016/03/inverter-graph2.jpg "Inverters for [cara_s] - and motor homes too 208")
This graph of a 3000-watt inverter shows it can output 7500 watts for 10 seconds,
4600 watts for 5 minutes and 4000 watts for 15 minutes.
Inverters for travel trailers – transformer type
Like camels, transformer inverters carry up to three times their full load for a few seconds. They may carry 50% more for a few minutes, and 10% or so more for 15-20 minutes. This ability is inbuilt – it’s not an overload. If that ability is exceeded they shut down to cool off.
A good 800-watt transformer type inverter runs a TV/DVD that draw 75-150 watts. It powers the odd kitchen appliance, like a coffee grinder, at the same time.
Inverters for travel trailers – switch-mode
These are less camel-like. Switch mode inverters are relatively cheap, light and compact and ultra-efficient. Their downside is almost zero surge capacity. Few even maintain rated output. Most maintain 80%, but some a mere 40% or 50%. They are valuable where space and weight is limited – and no overload capacity required. Caution is necessary when buying.
Inverters for travel trailers – temperature versus output
High-quality inverters are rated at an ambient 40º C and will run continuously at that. Cheap ones are likely rated at 25º C, causing them to seem more powerful and better value than they are. Outside winter, a quality 500-watt inverter may outperform an 800-watt cheap one. Be careful when buying. Some vendors quote output at low temperatures.
Inverters for travel trailers – standby current draw
TVs, DVD players, phone chargers etc often remain on overnight. For these, choose an inverter with low ‘quiescent’ current – i.e. that needed to run itself. This varies, but switch mode units have the least. Info is in makers’ technical data, but rarely sales brochures.
Inverters for travel trailers – electrical isolation
Many low-priced inverters have an ‘auto-transformer’. These have one side of the 230-volt output winding connected to the battery. This can be dangerous. Good quality inverters are electrically-isolated. They cost more but are much safer. Electronics supplier (Jaycar) sells only double insulated, electrically isolated units.
Inverters for travel trailers – buying
Switch mode inverters are smaller, lighter, more efficient and cheaper. They have less surge capacity and may need a 2000 watt such unit to start a 500-watt motor.
Transformer based inverters are larger and heavier. They cost more to buy and ship. Some are less efficient but have a high surge capacity. They suit loads that require a high surge current.
A microwave oven’s ‘rating’ (e.g. 800 watts) is a measure of the heat it generates. It is not its draw in watts. Most are only 50% efficient. An ‘800-watt’ microwave oven is thus likely to draw about 1200 watts.
If you can afford and accept size and weight, a transformer sine-wave inverter is a good choice. Otherwise buy a quality switch mode sine wave unit big enough to start and drive known load/s. Do your sums before buying: that needed can be five times the rating of the former.
With inverters, you get what you pay for. Buy a top known brand from a reputable supplier. Be wary of ‘badge engineering. There, identical units under different names may have varying levels of distribution. Each takes a profit!
Inverters for travel trailers – connecting appliances
This 2000 watt inverter has two 230 volt ac outlets. Appliances plug directly into these outlets. Inverters of this type must not be connected into fixed mains wiring. Pic: Projecta.
Some inverters have power socket outlets. Appliances plug directly into those outlets. These inverters must not be connected to fixed mains wiring. It is illegal and may prevent safety circuits from working.
Inverters intended for connecting to RV fixed wiring have no socket outlets. They are intended for direct connection (by a licensed electrician) to mains wiring. Such inverters rely on that system’s protection.
The complex rules (for RVs etc) are in AS/NZS 3000:2018, and in AS/NZS 3001:2008 (as Amended in late 2012)
Inverters for travel trailers – current draw
Even small inverters draw high current at full load. A 2000 watt, 12-volt unit may draw 400 amps on surges. This is much the same as a 4WD’s starter motor. If more than 1500 watts is required, it is better to use a 24-volt system. Above 3500-4000 watts requires 48 volts. Heavy cable must be used, and cable runs kept to a metre or so from the inverter to the battery.
Travel trailer and motorhome electrics, particularly inverters for RVs is a complex subject. Caravan & Motorhome Electrics covers it in depth. Solar That Really Works! covers all needed for solar in cabins and RVs. Solar Success is likewise for home and property systems. Every aspect of buying, use and even self-building is the Caravan & Motorhome Book. The Camper Trailer Book is likewise in its area.
Buying one or both books repays multiple times by your getting things right the first time. This is helped by my (Bio) joint engineering and writing/publishing background of over 60 years. This ensures my books are technically competent, and in plain English.
Travel trailer weight safe to tow – depends on what tows it
by Collyn Rivers
Travel trailer weight safe to tow
The maximum travel trailer weight safe to tow depends on what tows it. This article by Collyn Rivers explains why – and how to know what it is.
In earlier times, what travel trailers were considered safe to tow was based on their weight relative to that of the towing vehicle. That, however, was in an era when most new travel trailers were four or so metres long, weighed 1200-1500 kg (2650-3300 lb), and rarely towed above 80 km/h. Where that length and weight still applies, such trailer/tow vehicle weight ratio remains fine. It is true, for example of (sanely laden) camper trailers.
With travel trailers longer than 4 metres, the limiting weight largely relates to where the weight is distributed. If over 6 metres that weight distribution is critical. This applies both to design and loading.
Travel trailer weight safe to tow – why this matters
Here’s how to feel for yourself how and why this matters.
Hang any suitable bar (a broom handle will do at a pinch) by a rope. Add a couple of weights as shown below.
This bar simulates a travel trailer with the weight close to its centre. Hold the bar and turn it – like a travel trailer swaying. You will find that, even with heavy weights, it turns and stops turning with ease. Pics: rvbooks.com.au
Now try it with the weights like this:
This simulates an end heavy travel trailer exactly the same weight. Hold and turn it as before. You will find it surprisingly hard to start and stop.
The further apart the weights, the harder it is to start and stop moving. Also, (as with a tow vehicle and travel trailer) the lighter you are, relative to the length of the bar and position of the weights, the harder it is to stop and start moving. Take care if you try this with heavier weights. The force may push you over! The same applies if you use a longer bar. Try it also with a heavier weight at the rear.
If you do not access to a barbell and weights you can do this by holding a bottle of wine in each hand – then turn while turning rapidly fully extended both arms sideways. Do this on a still revolving chair and you may have a surprise. (Any wine will do, but drink it afterwards).
Moments along a beam
The above is known technically as ‘Moments Along a Beam’.
The ‘effect’ of weight on a pivoted beam (and a travel trailer chassis) relates to its distance from the pivot (axle). Pic: original source unknown.
Unless weight is more or less central, a short heavy van is safer to tow than a long van of the same weight. The see-saw effect also shows it is not good to have anything heavy at either end. Locate tool-boxes, batteries, spare wheels etc as close to the axle/s. Never at the far ends.
You have some control over this. The heavier whatever you load, the closer it needs to be to the axles. Never load anything heavy up-front and ‘balance’ that by weight at the rear.
Because of these effects, a long travel trailer needs a much heavier tow vehicle than a short travel trailer of the same weight. Some locally made ‘vans are (in my opinion) far too long to be towed safely by anything short of the big Fords etc.
Relates also to travel trailer length
You should have no problem towing a correctly laden 3.5-metre travel trailer by a laden tow vehicle the same weight. But you are pushing your luck with a 6 to 6.5-metre local product. I would only tow it with a vehicle at least 30% heavier.
If seeking a travel trailer longer than 7 metres I seriously advise readers to consider the dynamically more stable fifth-wheel travel trailer format.
For a warning and explanation of why many travel trailers are overweight see Travel trailer tare weight issues/
A more technical explanation is at: Travel trailer and tow-vehicle dynamics/
Information on tow ball mass is at: Travel trailer nose weight/
See also Why Caravans Roll Over – also Reducing travel trailer sway. For info on fifth-wheelers see Fifth-wheel travel trailers are safer/
If you find this article helpful you will find my books even more so. They include the Camper Trailer Book, Caravan & Motorhome Electrics, Solar That Really Works for RVs), Solar Success (for home and property systems), and the all-new Caravan & Motorhome Book. For information about the author – see Bio.
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Need for a WDH – avoid using one if possible
by Collyn Rivers
Need for a WDH
Long end-heavy travel trailers have a need for a Weight Distributing Hitch (WDH). For all trailers, though, it inherently reduces tow vehicle stability. Here’s how and why.
Typical WDH (weight distributing hitch) Pic: Jayco.
Need for a WDH – Tow Ball Mass
Within limits, travel trailers must be nose heavy. For light European-style travel trailers with (desirable) centralised mass and loading, the improvement becomes less when nose mass rises above 6-7 per cent of the total weight. These travel trailers neither have a WDH nor provision for one.
Locally made travel trailers, however, have become longer and heavier (some exceed 4.0 tonne). They need a high nose mass of at least 10% at all times. Such nose weight (up to 350 kg [770 lb]) however is imposed on a hitch that overhangs the tow vehicle’s rear axle. The effect is like pushing down on the handles of a wheelbarrow. It levers up the front wheels of the tow vehicle. This (in effect) lessens the grip of the (steering) front tyres.
To counteract this, a WDH (a springy semi-flexible beam) attached between travel trailer and tow vehicle, levers the front wheels back down. This wholly or partly restores the weight. But whilst partially fixing that frontal weight problem it inherently introduces another.
The WDH issue
Only too often overlooked, whilst a WDH assists the front end weight issue, it cannot compensate for yaw (snaking) forces.
The beginning of a jack-knife. Side forces on a tow ball cannot be corrected by a WDH. Pic: copyright rvbooks.com.au
Worse – by reducing the imposed nose weight on the tow vehicle’s rear tyres – it reduces their ability to counteract those yaw forces. That, in turn, causes them to run wide – in effect introducing the unstable result shown above.
Need for a WDH – how tyres behave
The area of a tyre in contact with the road (called its ‘footprint’) is about the size of a human hand. When the steering wheel is turned, the front wheel-rims exert a side force on the tyre walls. That, in turn, distorts their footprints, causing the vehicle to take up the desired direction. For the same reason, any side force will cause a tyre to have a steering effect. This includes rear tyres when subjected to yaw forces.
Here’s how a tyre behaves when steered – or subjected to a side force.
A correctly cornering rig follows the dotted line shown below – i.e. it runs very slightly wide. That running-wide effect is known as understeer. It automatically reduces the risk of jack-knifing. The red dotted line shows what happens if understeer is too great.
Pic: original source unknown.
When a heavy travel trailer yaws, the WDH’s reduction of rear tyre loading reduces their ability to resist the imposed yaw forces. This disturbs their required ratio of grip and slip angle action front/rear. If the rear slip angle exceeds a critical level the result is so-called oversteer. It may build-up to that shown below – dotted red line – where those (rear) tyres may lose all grip
If the rear tyres increasingly cause the vehicle to self-tighten the turn (oversteer), the result may result in final jack-knifing. Pic: original source unknown.
Travel trailer jack-knife in the UK – Pic: original source unknown.
Need for a WDH – adjusting a WDH
It has been known since the late 1970s that using a WDH to compensate for loss of tow vehicle front end weight prejudices the tow vehicle’s desired handling. If the WDH is adjusted to fully compensate it introduces a loss of cornering ability of 25-30%.
In physics terms, it reduces it from about 0.4 g down to about 0.3 g. (the ‘g’ refers to the force of gravity). A rough guide to this is that many local road authorities have ‘Recommended cornering Speed’ signs. cornering at that speed usually corresponds to about 0.2 g.
Despite this, until recently recommendations have been to adjust a WDH to fully counteract travel trailer nose ball weight. Now, however, following recommendations (in a major study – SAE J2807), the world’s major maker of WDHs (Cequent – Hayman Reese) advises adjusting to correct tow ball mass by 50% only. This typically results in the travel trailer‘s nose being lower by about 50 mm. This is desirable anyway as airflow under the front of a travel trailer tends to cause it to undesirably lift.
Need for a WDH – tyre pressures when towing
Regardless of using a WDH or not, when towing increase the tow vehicle’s rear tyre pressure by about 50-70 kPa (7-10 psi). This virtually restores the previous steering characteristics. Do not vary the tow vehicle’s front tyre pressure: that should be whatever the vehicle maker advises.
Need for a WDH – summary
The above issues have long been well understood. They have been substantially addressed in the EU, and also followed by EU travel trailer firms now building travel trailers in Australia. They are also covered in associated articles on this website. Be aware that a WDH should only be used where necessary. This typically where the laden travel trailer is heavier than the laden tow vehicle. Also for most travel trailers over 5.5 metres (approx. 18 feet).
Need for a WDH – further information
The general topic is covered (more technically and in-depth) in my article Travel trailer and Tow Vehicle Dynamics. See also Reducing travel trailer sway, also Making travel trailers stable
See also the excellent UK/EU related: caravanchronicles.com/guides/understanding-the-dynamics-of-towing/
If you found this article of value, my books will prove even more so. They include Caravan & Motorhome Electrics, Solar That Really Works (for RVs), Solar Success (for home and property systems), and The Camper Trailer Book. The author’s Caravan & Motorhome Book covers every aspect of the subject matter.
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* Darling J., Tilley D., and Gao B., 2008. An experimental investigation of car-trailer high-speed stability. Dept of Mechanical Engineering, University of Bath, UK.
Caravan tare weight issues – some declared weights may not be correct
by Collyn Rivers
Travel Trailer Tare Weight
Travel trailer tare weight issues mainly arise about what’s included and what’s not. Water is not, nor may be optional extras. This article reveals all.
Legally, travel trailer tare weight is called Tare Mass. For the purposes of this article you can regard ‘Mass’ as the same as weight. It refers to it accordingly.
A typical Compliance Plate. Tare Mass here is 2280 kg. The ATM (see below) is 2680 kg.
Tare Weight issues arise
A travel trailer‘s Tare Weight is what it weighs when it leaves the factory. It should include everything specified at the time of ordering. This weight must show on a Compliance Plate attached to the travel trailer chassis. The travel trailer‘s weight ex-dealer, is often higher.
Most travel trailer makers produce standard products. It is dealers who may provide and install all optional extras, even if order specified. Such options include air conditioning, solar, batteries, etc.
Personal allowance
A travel trailer maker typically allows 250 kg (550 lb) for single axle travel trailers under 1500 kg, and about 300 kg for larger/heavier single axle travel trailers. Travel trailers with two axles typically have 400 kg.
Few buyers know that Tare Weight excludes the (1 kg/litre) of water. There may be several tanks, totally 80 to 350 or more litres. It includes the weight of one 9 litre gas cylinder – but not its (approx 9 kg [20 lb]) of gas. While less common now, Tare Weight may even exclude drawers and mattresses.
The Travel Trailer Industry Association of Australia, warns: ‘items fitted to the travel trailer after it leaves the manufacturer’s factory are not considered to be part of the Tare Mass.’ The industry does not keep this secret, but vendors will rarely tell you this when you order.
Aggregate Trailer Mass (ATM)
The ATM is the travel trailer maker’s specified maximum weight (uncoupled), with full allowed load. It is a rating assessed by the travel trailer maker. The ATM is based on chassis strength, tyre and axle loadings etc. You must not exceed this weight. The difference between Tare Weight and ATM is the Personal Allowance. It is all that can be added.
The personal allowance is an industry recommendation. For single axle travel trailers under 1500 kg, it is 250 kg. For dual axle travel trailers it is 350 to 450 kg. It applies also to fifth wheel travel trailers. There is no legal requirement except ‘fitness for purpose’.
Travel Trailer Buyers Guide informs ‘that may well include ‘gas, water, food, drink, personal items, pots and pans, crockery, cutlery, clothing and any accessories added by the owner of the travel trailer after purchase.’
Gross Vehicle Mass (GVM)
This is the loaded travel trailer weight when coupled to the tow vehicle. It excludes the weight on tow vehicle. The GVM is legally a maximum rating set by the travel trailer maker.
How to avoid travel trailer tare weight issues
To avoid travel trailer weight issues, insist a legal contract includes options within Tare Mass. Unless you do, extras are legally within the ‘personal allowance’. Ensure the contract specifies every optional extra. Require all to be included in the Tare Mass. Ensure the contract requires the travel trailer be weighed in your presence. Do this on a Certified public weighbridge. Furthermore, compare that weight against claimed Tare Mass. There will be minor discrepancies – but within 1% or so. Resolve any discrepancy before you finalise paying.
Resolving travel trailer tare weight issues
When you buy through a dealer, that dealer must legally resolve issues. The dealer may