RV Power Solutions

Michael Browning — 6 March 2015

For most of us, 12V technology is a black art we would love to master. Unfortunately, we usually only uncover our own inadequacy, and that of our system.

Understanding what your essential 12V appliances need to keep them functioning correctly in remote areas is an essential part of pre-trip preparation, as is appreciating what other demands you are likely to make on them.

So how much power do you need and how do you get it reliably? A good starting point is to check with an expert and Alan Johnson, founder of Melbourne’s Piranha Offroad Systems, is regarded as an authority on automotive electrical systems. As a result, Piranha is one of the world’s largest manufacturers of dual battery and other alternative offroad systems.

Alan took us through the basics, so let’s start at the beginning…


Equipping your tow vehicle correctly is vital as it is the primary ‘generator’ most people will use to replenish their RV’s battery (or batteries).

There is room under the bonnet of most 4WDs for a second battery, whose dedicated task is to support the 12V accessories in your tow car and those in your caravan.

When connected properly through a modern battery management system, it is charged when your vehicle is running, but drains independently of your starter battery when powering appliances. So if you run it flat while running your portable fridge, it won’t affect your starter battery’s ability to fire up your tow car in the middle of the Tanami Desert.


To keep your caravan’s batteries charged on the go, your tow vehicle needs to have a strong electrical connection to it.

Regular nine-pin round or 12-pin flat plugs deliver power to a range of things on your caravan, from brake lights to indicators, but they usually don’t carry sufficient current to keep a bank of deep-cycle batteries charged.

Piranha, like most specialists, recommends fitting a separate Anderson plug that takes its power directly from your car’s main or, ideally, second battery. These are usually rated at 50A, and can take even more current, but only if sufficiently large diameter wiring is used. Otherwise, the full current won’t make it down the 10m or so from your tow car’s battery to its mates in your van or camper.


If your power needs are fairly small, you can probably get away with a single 100Ah deep-cycle battery in conjunction with a solar panel on the roof and a good charging system. However, most people today will need more than a single battery of this size in their caravan.


Inverters are a great idea to run a range of things with heating elements, but they are power-hungry devices. Think of them as a bank. The more you withdraw from your RV’s batteries, the less you will have to spend.


Modern ‘smart’ alternators in today’s cars turn the alternator off, or limit its output whenever they can to maximise fuel economy and this can reduce the charging current getting through to your van’s batteries on the move.

The way to get around this is to fit a modern DC-DC charger that will take whatever voltage that is available and will step it up to match the voltage and the chemistry of the battery you have in your RV.


The choice and price range can be bewildering. The most basic battery you can buy is a typical flooded, wet cell lead-acid battery, which has been around for more than 100 years and comes as a deep-cycle, hybrid or cranking battery.

Next up the ladder are the slightly more expensive calcium-type batteries, which charge a bit quicker than a regular wet cell battery and have a longer shelf life.

Finally, amongst conventional batteries, we have AGM batteries. The ‘AGM’ stands for ‘absorbed glass mat’ and come in two varieties.


If you are travelling in relatively cool temperatures, such as in the Victorian High Country, a three-way (240V/12V/gas) fridge is adequate, but in really hot or tropical weather, a dedicated 12V or ‘two-way’ (12V/240V) compressor fridge is more efficient.

However, as the compressor fridge switches on and off continually to maintain the required temperature, it drains your 12V system.

The full feature appeared in Caravan World #536 April 2015. Subscribe today for the latest caravan reviews and news every month! 


power RV 12V


Michael Browning

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