Ask The Mechanic – Split Charge with Leisure Battery

A leisure battery allows you to use 12v appliances such as fridges, lighting and heaters etc whilst camping without running your main vehicle battery down, so you can still start the engine the next day!
There are several ways of keeping this leisure battery charged, the most popular is using a split charge system, this system charges your leisure battery and main battery whilst driving, using your engine’s alternator.

There are kits available online for split charge systems. Once again, Just Kampers sell these kits at reasonable prices and comes prewired for easy installation.

When installing a split charge system, before you start work, remove the earth (marked negative) lead from your main vehicle battery. Depending on your type of van, your leisure battery will need to be located in varying locations. The design of the Bay Window makes it ideal for a leisure battery install as there is a spare tray on the left hand side of the engine bay. So for this quick guide, we will use the bay window as an example.

From the spare battery tray on the left of the engine bay, where the leisure battery will be fitted or is already fitted, lay the pre-rewired wiring loom across the back of the Bus, routing from left to right.

A good place to locate the relay itself is on the left hand d-post inner structure. Hold it in position and mark the top locating hole. Drill this and mount the relay using a suitable self-tapping screw. The wiring loom for the rear lights runs along the top of the inner engine lid hinge panel, held in place with metal tabs. Carefully prise these open and locate the new section of loom within.
Alternatively, use cable ties to hold the new loom to the existing wiring.

Remove the positive lead from the main battery and secure the new power lead under the battery clamp nut.

There are just two wires on the split charge relay. The brown wire goes to earth (we utilised the existing tail light earth for this) and the red (positive) wire needs to go to a switched live. For this, we routed the cable under the engine bay tar board and piggy backed it to the switched live terminal on the ignition coil.

With the leisure battery in place, install the auxiliary fuse box loom under the battery clamp nut. Then locate the fuse box on the rear inner wheel tub.

Next, install the leisure battery earth lead. This must be bolted to a good earth point.

Finally, you don’t want your new battery sliding around, so we used a universal battery clamp to secure ours in place. Once installed, connect the positive leads on both batteries, then the two earths. All should now be up and running, just leaving you to wire any accessories forward from the new fuse box.