Fitting a Split Charger to a VW T5 Campervan

In this article we are going to have a quick look at my van electrics and how I fitted my split charge relay.

A split charge relay is, as the name suggests, a relay that once activated transfers power from one thing to another. In this case, it is used to charge my leisure battery. Essentially the main van/car battery in the engine bay has a charge of somewhere in the region of 12.6 volts when the engine is off. In order to maintain this 12.6 volts, the battery needs to be charged to allow things like the main van headlights or stereo to work and if it is not charged it will go flat like any other battery and the van won't be able to start. When the engine is running it is the job of the alternator to charge the main van battery and an alternator supplies a charge of around 14.5 volts to the main battery to keep it topped up when the engine is running.

I installed my leisure battery, split charger and fuse box under the double passenger seat and used a grounding point under there. The bottom green arrow shows the power coming in from the engine (note the thicker gauge cable) and the top arrow shows the cabling going out from the leisure battery to all the different circuits in the van e.g. USB charging points

A split charge relay,allows some of this charge from the alternator to be diverted to the leisure battery as well. It is the leisure battery that operates all of the 'leisure' electrics such as USB charging points, interior LED lights, pumps for water for the sink etc and so this needs to be kept charged as well as otherwise these things will stop working. Essentially the leisure battery is 'daisy chained' from the main van battery in that the positive terminal from the main battery is linked to the positive terminal of the leisure battery. The split charge relay is a clever bit of kit that senses (VSR - volt sensing relay) when the engine is running as it looks for a voltage of around 13.5V and then it opens up to allow the alternator of the engine to charge both the main battery and the leisure battery when the engine is on. This keeps them both charged and when the engine is turned off the split charge relay interrupts the link to the leisure battery and stops the flow of current between the two batteries as the voltage has dropped below 13.5V. In this way, you can camp for a weekend and use all the power from the leisure battery, knowing that come Monday morning the engine will still start so you can drive home because the relay has isolated it from the leisure battery. The leisure battery then gets charged as you drive.

Everything you need to complete this project can be bought from Amazon for £80 in a kit by clicking the image below

I installed all my electrics under the front passenger seat including battery, split charge relay and fuse box. I had to drill holes to feed the cable through the seat base and it is important to place rubber grommets in the holes to stop the cables from chaffing. See the arrows below.

The picture above shows the incoming and outgoing circuits and the picture below shows the 12v fuse box installed on the inside of the passenger seat

The actual split charge relay is shown below:

The wiring pattern is basically: Engine battery >> Pos terminal feed >> 100a fuse >> Bring inside the van to the passenger seat (see below) >> Split charge relay >> 100a fuse >> Leisure battery >> Fuse box >> Outgoing circuits.

To bring the cable from the main engine battery inside the van you need to remove some trim inside the engine bay to expose an existing grommet. Remove the two nuts shown below:

This trim piece then slides off and you need to drill/grommet a hole for the main feed to pass through:

Pass the cable through the bulkhead (hole already exists) and it will appear behind the glovebox. All you need to do then is route it under the floor seals to the passenger seat:

If you have any questions on this, please comment below.


To buy the parts shown in my articles at the very best prices possible, please visit the T5iver shop here