Van Tour: Split Charge Relay

As with all vans you see on Instagram you have no idea what’s really under all the wood and panelling and our van is exactly the same. Based on the questions we get from you guys we thought we would pull back the curtain a little and talk you through what went on during our self build conversion from panel van to camper van.

photo credit: The Indie Projects

What is a split charge relay?

A split charge relay allows us to simultaneously charge our leisure battery and our starter battery from the engine’s alternator. Normally when you drive your car (or van) your starter battery will be charged by the voltage produced by the engine’s alternator. You are able to connect your leisure battery to your starter battery so that the alternator will then charge both batteries at the same time.

You can connect these two batteries simply with big enough cables so why do you need a split charge relay? When you connect both batteries they essentially work as one big one which means when you run your electronics from them they will drain both batteries. If you drain your starter battery too much you won’t be able to start you car. A split charge relay will prevent you from draining both batteries when running all of your electrics.

It does this by disconnecting the two batteries and thus making them separate again so that when you run your electrics you simply draw the power from your leisure battery. How it disconnects the batteries is dependent on the type of split charge relay you choose to install.

Manual Switch

As the name suggests a manual switching relay is simply a switch you flick to connect the batteries and switch off to disconnect them. The biggest benefit to this type of set up is that is is extremely simply to install and the most inexpensive type of relay.

The downside to such a relay is that it is entirely dependent on you remembering to either switch on or off the relay, forgetting to do so will either end up on your leisure battery not charging or worse your starter battery going flat leaving you stranded.

Automatic Switch

An automatic switch relay connects directly to the engine’s alternator and senses the increase in current it produces. Once it sense this increase it will connect the two batteries together and begin charging them both. Once it detects this current has stopped being produced by the alternator it will disconnect the batteries thus protecting your starter battery.

Although more expensive than a simple manual switch the automatic switch is still relatively inexpensive however the downside is that it requires you to connect directly to the van’s alternator, which although simple, does require a little knowledge of engines and also running cables from the engine bay to your battery bank.

Voltage sensing relay

The split charge relay we decided to install into our van is a voltage sensing relay. It senses the voltage of our system and if it rises above 13.3V it will connect the batteries together, this means that either the alternator or the solar set up we have will trigger this as long as the current rises above 13.3V. When it senses the current drop below 12.8V it will disconnect the two, protecting our starter battery from being drained.

Although this is the more expensive (relative to the other two relays) it was the one which was both simple to install as well as most reliable for us to ensure we don’t drain our starter battery.

For further Van Tour reading why not have a look at our van tour page where we will be adding more in depth information about the specifics of our van!