12V Camper Modifications

David Cook — 4 April 2016

For many of us, the purchase of a new camper trailer – whether it’s brand new out of the factory or purchased second-hand from a previous owner – is an act of faith in fulfilling the dream. Some manufacturers go all the way no matter the cost, while others strive for the bottom line, labelling their products as ‘priced from…’ so buyers can add items to suit their budget.

Campers’ expectations, however, have changed considerably. Practical experience shows it’s now not always enough to have a battery, and a charger, and a solar panel with various wire and plugs attached. We’re now wondering if the battery big enough or of the right type and should there be a second or even a third? Is the charger big enough? Is the solar adequate to keep pace with our increased demands? Is the cable adequate to move electrical current around at the right pace without strangling the voltage?

For many campers, their circumstances may change – say, they want a bigger fridge or more lighting – and technological developments such as newer batteries or chargers may leave their setup wanting. So, as a consequence, they take to modifying their camper’s electrical arrangements themselves.

We spoke to three experienced campers at a recent weekend getaway on the New South Wales north coast about the approach they’ve taken. Often the changes may seem small, but these can open up a system’s capacity and make a big difference to its performance.

Craig Quinn

As the president of Sydney and Central Coast Avan Group, Craig Quinn pushes his Avan Cruiseliner to its limits, thanks to a few electrical modifications he’s made.

The 2011 camper was equipped with a 90Ah AGM battery, a mains charger, incandescent lighting and just enough current coming in through the standard wiring from the tow car’s alternator to run the power-hungry three-way fridge. It was fine if you were happy to spend much of your time in a caravan park, where you could plug your battery into the mains and run your fridge on either gas or the 240V, but Craig soon discovered he liked having full access to his rig’s comforts away from the organised and manicured world. So an electrical remake was on the cards.

Craig’s rejigged Avan now has a new lease on life and has since taken him – with care – to many out of the way campsites.

Battery Box

Craig invested in a battery box package from JTS Online. It came with a 120Ah AGM battery, an Anderson plug input, two cigarette sockets, a Merit socket, digital voltmeter and everything fused so it was a quick shortcut to electrical independence.

To bring this to life, he installed a dedicated cable to an Anderson plug at the hitch which he mated to one in his tow vehicle, so now the battery charges as he’s driving.

Accessory Plugs

Craig installed the 12V cigarette plug, a dual USB outlet and digital voltmeter in a side-facing three-bay housing in a drawer cabinet near the foot of the bed, which he felt was less exposed compared to the factory fitted sockets.

The digital voltage readout, which keeps him apprised of the battery condition, has a powerful light that shines in his eyes when he’s trying to get to sleep, so he’s currently devising a cover to counter it.

Extra Length

Avans have a side gland, beneath a cover, to access various services for the trailer’s requirements. The standard fitting includes 15ft of 15A cable, hard-wired into the camper to connect to mains power.

Craig had this disconnected and a 15A male plug installed under the bed, adjacent to the gland, as well as a 10A power board, which enables him to connect whatever length 15A or 10A power cable he might desire to use.

He also added an Anderson plug (he standardised all his 12V power plugs on the Anderson format) just inside the gland so that he can run in a lead from the solar panel or to take a 12V extension lead out to an external shower tent.

Fridge Management

While the three-way fridge does the job for Craig, it is very hungry on 12V (as are all three-way fridges), and it has been measured drawing a hefty 14A.

This could rapidly flatten even a 120Ah battery, so Craig has installed a Fridge Switch from RV Electronics.

The Fridge Switch senses motion and vibration, and when this stops – as when the vehicle stops – it will automatically turn off 12V power to the fridge.

Craig also installed a Topargee water gauge which measures water usage from the tank in litres, rather than a fraction of its capacity.

Terry and Sandy Agland

Terry and Sandy Agland are very experienced offroad adventurers who built a very capable camper trailer of their own (which they still own) before moving on to an upmarket Australian Off Road Eclipse Super Camper in December 2013.

While the Eclipse camper ticked many boxes, it didn’t stop Terry from “fine tuning” his new camper.

Light Show

AOR doesn’t skimp on its external illumination, and Terry and wife Sandy found it a bit much. So he rewired the two LED lights to separate switches, allowing the couple to turn on one at a time.

Terry is also considering wiring in a dimmer or adding a diffuser to further soften the light, and wants to convert one of the lights to a yellow colour to discourage insects.

Power to the TV

Terry found the perfect spot to install a TV in the camper, except that there was no power outlet nearby, requiring him to run a long lead. So he installed a dual 12V outlet for this purpose, permitting him to run the 12V television and a masthead amplifier for the antenna.

He’s also found that, with a USB adapter socket plugged in, it’s a handy place for charging phones and other 12V appliances.

Tracing a path

Terry didn’t have a diagram when he redesigned the system, so he traced every single wire in the electrical box and made his own. In the process, he discovered a battery relay near the tow vehicle connection which duplicated one he had already installed in the car, so it was removed. He had also found that his dual 120Ah batteries were losing charge in storage. He suspected a low voltage disconnect system, which drew 300mAh to monitor the batteries’ voltage, might’ve been the cause, so he removed it and hasn’t experienced problems since.

Terry also inserted a 20A circuit breaker in the circuit for the solar panels so he can turn off the solar and run solely on the DC-DC charger if desired.

To 12 Pin or Not

When Terry wired up his first camper trailer, he did it using a 12-pin plug at the hitch, with the 6B&S cable from the alternator in the vehicle being split into three and shrink wrapped each strand to a separate wire running to three pins in the plug allocated to power. This worked well for Terry, so he decided to replicate it in his AOR.

“I just see it as one less plug to worry about when hooking up and disconnecting,” said Terry.

“I don’t necessarily say the 12-pin plug is any better than a 50A Anderson plug, but in nine years it has never let me down.”

The DC-DC Advantage

When Terry ordered his camper, he did not specify a DC-DC charger. However, he soon found that his new batteries wouldn’t fully charge between camps, and, when he checked, he found he had 14.2V at the alternator and 13.5V at his LandCruiser’s rear bumper because of voltage drop down the cable.

By the time he’d run the charge back the full length of cable from the hitch, it was down to 12.9V at the batteries, which is not enough to top up batteries designed to be charged at 14.2V.

He fitted a Redarc BC-DC 1220 charger which has done the job excellently since. He chose this unit because it doesn’t have an inbuilt solar regulator, as the Morningstar regulator for the 300W roof-mounted solar was doing an excellent job.

Fridge Maintenance

Terry improved the performance of his fridge with large vents on the side and above the compressor and condenser. He also installed a large computer fan to blow air across the compressor on hot days and a programmable digital temperature controller for $15.

The controller lets him set the fridge’s hysteresis (the lag in its response to changes in its environment) from 5°C to 1°C. Now, if the fridge is set to 4°C, it will switch the compressor on at 5°C instead of 9°C (5 °C higher) making it easier to maintain the desired temperature.

To minimise power consumption some fridges cut out when the ambient temperature drops, as indicated on a wall-mounted sensor, but if the weather remains cool for a long period, freezer temperatures can rise. Manufacturers sell manually-operated kits to overcome the issue, but Terry prefers his digital controller, as it’s mounted inside the cabinet rather than on the wall.

Ken and Olga Rumble

Ken and Olga Rumble know 4WDing – they ran a 4WD training school for many years – and chose their camper appropriately: a Challenge Outback, which they purchased new in 2004.

“We ordered it pretty much standard,” Ken explained, “and it has performed brilliantly, with next to no problems from day one.”

That doesn’t mean that Ken has left the electrics alone, and as he went along, he decided to upgrade the standard electrical setup to keep up with his needs.


The factory supplied setup included two 90Ah calcium batteries. But, as they required more than 16V to fully charge, they relied soley on an 8A charger. So he had two 130Ah AGMs and a 10A Engel DC-DC fitted, and then later installed a seven-stage Projecta 15A charger.

Anderson Solution

A popular solution at the time was to use a single pin in a seven-pin plug to connect charge from the alternator to the camper. But as his electrical demands increased, Ken rewired the hitch point with a separate circuit, connected through a 50A Anderson plug.

Inverter and second fridge

Ken installed an Anderson plug on the bulkhead behind the zip-open panels on the camper’s drop wall, inside the tent. This was connected to the batteries, and gave him access for power to run a 600W inverter to run 240V appliances.

He also installed a 6mm cable through to the rear of the camper so he could power a new Merit plug for a second (30L) Waeco fridge for a round-Australia trip. Such ventures are best assured by a second cooling system in case of emergencies.

Top up solar

Ken decided to run 120W of solar on his Prado’s roof racks, where it can keep up the charge in the car’s second battery, a 110Ah deep-cycle, as well as be available to the camper simply by plugging in to the Anderson plug on the back of the vehicle.

It charges through an MPPT regulator and in a round-Australia trip sustained all batteries, and a 50L Waeco fridge at -8°C.

Power on

The original setup came with two fuses and a digital voltmeter. For security and scalability, Ken added two more fuses, a 12V main safety switches and a more efficient voltmeter to ensure everything works well now and into the future.

Check out the full feature in issue #99 April 2016 of Camper Trailer Australia magazine. Subscribe today for all the latest camper trailer news, reviews and travel inspiration.


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