These days it’s getting more and more common to find 4WDs, utes, vans and campers that have some sort of dual battery setup for camping.

There is always a starter battery to start the engine, but most campers, overlanders or off roaders will fit an auxiliary battery (also known as a house battery) to their vehicle that allows them to run a camping fridge and other electrical accessories much more reliably.

One of the most important considerations when looking to install a dual battery system is the battery type – ideally you’ll want a Deep Cycle Battery.

WHAT DOES DEEP CYCLE MEAN?

Deep cycle batteries are designed and built differently when compared to traditional starter batteries. Your starter battery is designed for a sudden and short burst of power as it starts the engine. This is a ‘shallow’ cycle because the battery is only discharged for a short burst and is then recharged.

A deep cycle battery is designed to be deeply discharged – slowly and over a longer period. They generally use thicker or larger lead plates inside, that minimise internal build up and ensure there is more material for the batteries’ internal chemical reaction to occur, for longer use and a more constant power output.

On the other hand, starter batteries use a larger number of thinner lead plates to increase surface area – this allows them to put out short bursts of high current required to start a vehicle, but the thinner material means build up occurs fasters, preventing the chemical reaction required for power andmakes them more likely to fail if discharged down to a low capacity over and over – if you try and use a starter battery as a camping battery, you’ll shorten its overall life.

TYPES OF DEEP CYCLE BATTERIES

There are many different types of deep cycle batteries– there are standard flooded lead acid batteries that use a liquid inside and need to be checked and topped up over time. There are maintenance free batteries that still use a liquid electrolyte, but are sealed and can’t be topped up and there are also new and expensive technologies like lithium batteries.

Arguably the best value and most suited to camping, 4WDing and overland travel is the AGM type. AGM stands for Absorbed Glass Mat and it simply means that inside the battery there is a tight mesh of glass fibres that actually absorb and hold the electrolyte in place – this has a few very important benefits.

1. AGM batteries can be made to be a leak-proof non gassing design so they’re safe to be used inside your vehicle cabin (not just in the tray or ute tub)
   
   
2. They ensure better contact between the electrolyte and lead plates, as the electrolyte is held in place
   
   
3. AGM batteries offer better performance than standard flooded deep cycle batteries
   
   
4. They’re highly vibration resistant due to their design
   
   

CHARGING AN AGM BATTERY

AGM batteries need a specific charging voltage to make the most of their extra power though – while some flooded batteries will charge at around 14 volts, AGM batteries can need as high as 14.6V for a full charge. If charging at home, choose a charger that is capable of charging AGM batteries – while if you want to charge in your vehicle while driving or with solar power, the best option is a DC-DC charger with AGM function – this takes the power from your vehicle’s alternator / starter battery and outputs the correct voltage that’s required to fully charge your second battery.

WHERE TO PUT YOUR AUXILIARY BATTERY

Where you position your second battery will depend on two main factors; first, your specific vehicle, setup and layout and second, your deep cycle battery type.

Flooded deep cycle batteries should not be used inside your vehicle and are more suitable for use under the bonnet or in the back of a ute or pick up. This is due to the fact they are not sealed and will vent gas as they’re used. This gas is flammable so avoid ignition sources or sparking electrical connectors near the battery.

Sealed AGM batteries can be used safely inside your vehicle – just ensure there are advertised as being a sealed non-gassing, leakproof design. They are also suitable for use in the back of a ute, however most types do not cope well with extreme heat and therefore you should avoid mounting your AGM deep cycle batteries under the bonnet.

Whether you want to install a dual battery system, upgrade your existing setup or simply want the ideal camping electrical system, make sure you’re using a deep cycle battery!