Adding a leisure battery will allow you to run lights, pumps, heaters, phone chargers, fridges and audio visual equipment without running down the vehicle battery and potentially leaving you stranded. It’s not a complicated procedure and vehicle electrics are relatively straightforward so it’s a job that should be within the grasp of most confident DIY camper van convertors. Having said that, it’s important that vehicle electrics are correctly configured and all circuits and installations are correctly designed and properly installed so if you are not completely confident in what you are doing here, it’s best to get professional help and advice. A short circuit poses a serious risk of fire so don’t take any chances in this regard.
My camper van electrical circuit included a 12v leisure battery and a 220v inverter and an external mains hook up. Let’s look at the split charging circuit in this article and I’ll cover the 12v and the 220v circuits separately.
The difference between a leisure battery and a vehicle battery.
The important point here is the difference between the two types of battery. A standard vehicle battery is designed to provide a large amount of current in short bursts, i.e to power the starter motor. A leisure battery on the other hand, is designed to provide smaller amounts of current over a prolonged period of time and also to be fully discharged before being charged back up again by running the engine. Leisure batteries are also referred to as ‘deep cycle’ batteries for this very reason. Using a standard vehicle battery for your leisure circuit will result in a very short battery life.
The charging circuit.
Adding a leisure battery to your camper van is one thing but you will also need to hook it up to the charging circuit that recharges your vehicle battery. To do this, you will need to fit a split charging circuit. This type of circuit includes a specially designed voltage sensitive relay which allows the leisure battery to be connected to the existing alternator in parallel to your engine battery. The split charge relay prioritises the engine battery and automatically switches to the leisure battery once the engine battery is fully charged. The circuit itself is very simple and complete split charging kits are readily available from camper van parts suppliers.
The leisure battery.
I chose a 115ah (Amp-hours; What does this mean? It will supply 115 amps for 1 hour or 11.5 amps for 10 hours) deep cycle battery from Halfords for €126. The battery itself is a bulky, heavy item so I opted to install it over the back axle, and under a false floor in the storage compartment. There was plenty of room here for the battery, the 220v inverter, an onboard battery charger and the water pump and plumbing. Locating the battery over the rear axle was also ideal for weight distribution so this location made a lot of sense.
Installation and wiring.
Once I positioned the battery, I screwed some timber battens to the floor to keep it in position. The split charge relay was screwed to the timber of the seat base right beside the battery. Once it was in place, I just had to run the cables.
The negative cable is secured to an earthing point in the bodywork and connected to the negative terminal of the battery. I made use of an existing threaded bolt hole in the bodywork for this. The positive cable runs from the positive terminal of the vehicle battery all the way back to the split charge relay, and from there, on to the positive terminal of the leisure battery (a 100 amp fuse is installed on either side of the relay terminals). A smaller negative wire from the relay then connects to the negative terminal of the vehicle battery and once this is in place, the split circuit is complete and fully functional.
The spilt charging kit I bought came complete with all cables, terminals, fuses, cable ties and conduit needed so it was just a matter of installing everything. Properly crimped connections are essential here as a loose connection is a serious fire hazard so don’t try to make these connections without the proper tools. I managed to borrow a heavy duty cable crimper from an electrician which was essential for making sound connections to the battery terminals. Cutting, crimping and assembling all the cables and connections is relatively simple and the whole installation only took a couple of hours.
Once the battery and split charge circuit are in place, you can run a 70 amp positive cable from the leisure battery terminal to a simple, blade fuse holder and start building your circuits.