Battery Setup for a fridge in a 4Wd

There are several factors to consider when setting a fridge up in your vehicle. How much capacity do you need in a fridge? Will you use it as a freezer? Do you have a dual battery system in your vehicle? How will you access the fridge?

Your vehicle battery setup is probably the main impediment to successful fridge operation. Dual battery setups with a suitable isolating device allow independent power to the fridge when the vehicle engine is not running is imperative for multi-day camps. This leaves the main battery fully charged for its primary role of starting and running the vehicle. However, even a dual-battery vehicle needs to be set up with care. Whilst a 40-litre fridge running as a fridge will perform well on a standard deep cycle battery over the course of one day, that same fridge used as a freezer will deplete the battery more quickly. A larger fridge or hotter ambient temperatures will also drain more battery power, while multiple days spent in camp without additional battery input will almost certainly be unsustainable and lead to trouble. Fit the largest auxiliary battery (in amp/hours) as possible, or even consider a third battery of the same type and size connected in parallel with the auxiliary. Absorbed glass mat batteries are worth considering for several reasons: they are more robust, physically smaller and lighter for a given amp/hour rating, and most importantly, accept a charge more quickly than a standard lead acid battery.

Vehicles without a dual battery set-up can still use a fridge, with some restrictions. The fridge should be set to a low temperature during the day while you are driving (when excess battery power is available) and then raised to a higher temperature (so that the compressor cuts in less frequently) during the night when you are camped. Another option is to leave the fridge set lower, even to freezing, and adjust the battery cut out on your fridge to its highest setting, often 11.5 volts, which electrically disconnects the fridge, while still allowing sufficient power to start the vehicle the next day. This is fine so long as the battery is in top condition, and the following morning is not too icy. It makes good practice for all travellers to set their fridge cut out to its highest level, as batteries suffer internal damage with deep discharging, which will shorten their working life and ability to store a full charge. Most battery damage is the result of excessive discharge, rather than structural damage, and even only occasional running down in voltage will have a negative cumulative effect.

Single-battery vehicles can also consider installing the largest battery that will physically fit into the vehicles and with a greater amp/hour rating than that specified by the vehicle manufacturer. This won’t harm the vehicle and alloys have more capacity for fridge operation. Other strategies include keeping an insulated/ protective cover on the fridge, limiting time with the fridge lid open, and using a portable solar panel to catch the afternoon and morning sun for battery top-ups (bearing in mind that a solar panel will not run the fridge directly, it can only trickle charge the battery supplying the fridge).

Maintaining adequate airflow around the condenser fins of the fridge should also preserve thermal efficiency. This will require that the fridge be restrained with an air gap between the appliance and bodywork or luggage within the vehicle. The rear storage area of a wagon-type vehicle is ideal, but the rear seat can be used at a pinch.

In either case, tie the fridge down securely, or for greater convenience, use one of the slider mechanisms that allow the appliance to be accessed and slid out from the rear of the vehicle. Some types of sliders even drop down on a pantograph mechanism to make searching for that elusive item at the bottom of the fridge an almost pleasurable experience.

Electrical connection within the vehicle is best done directly, rather than using the quite inadequate 12-volt outlets throughout a vehicle that generally allow the plug to vibrate out. Wiring to the fridge requires a minimum of 6mm cabling with a suitable fuse (say 20 amp) located at the battery. Keep the cabling well protected by sheathing or similar, especially where it is routed through metal holes or over sharp edges. Tie the loom well along its length and fit a suitable plug and socket at the fridge itself.

A well-setup fridge is the centrepiece of a good 4WD camping outfit and well worth spending the time and money on getting it right first up. Once done correctly, every trip will be more pleasurable for the entire group and allow extended off-road adventures far from the nearest shops. Talk to others about their experience and think long term, it’s more than likely a quality fridge will outlive your current vehicle by many seasons.