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A beginners guide to leisure battery charging and wiring

Updated: Feb 9, 2022

Today we will cover what battery and charging system your van already has and what you will need in order to start adding a camper van leisure battery system.

All images in this blog are courtesy of Rayne Automotive. You can find a link to all of their high quality camper van electrical kits throughout this document and our products page.

Why can't I use my vehicle battery to power my leisure electrics?

Every van that drives out of the factory will have a battery fitted. These are usually under the bonnet but can sometimes be located under the floor in the cab or under one of the front seats. The owners manual or a quick google search will tell you where yours is located.

A vehicle battery is designed to start the engine. This means that it uses a lot of its power at once to kick start the van, not to trickle out power for lights and fridge over a weekend.

A leisure battery is designed to discharge slowly, meaning it will keep your lights on, your tablet charged and the water pump running the whole trip.

If a vehicle battery is used for the leisure electrics you may find yourself stranded at the campsite on a Sunday afternoon. Yes, the vehicle battery will have the capacity to run the leisure system for a short period of time but once it has done this then you are not going to have the power left in the battery to start the engine to drive home.

How do I charge a leisure battery?

There are three main ways of charging up your leisure battery that we use at Combe Valley Campers. These vary in price and also vary in importance depending on your circumstances.

Method one- Split charge relay

This is the most common leisure battery charging method used and is fitted to nearly every van. A split charge relay is effectively a switch, that when closed connects the vehicle and leisure battery together. This enables the vehicle battery, once fully charged to split the charge it receives from the alternator with the leisure battery.

There are three main types different types of split charge relay that use different methods of closing the switch:

Ignition triggered relay - The switch is closed by an electric signal. In this case, a 12vDC signal when the ignition is switched on.

Voltage sensitive relay - The most popular option. The switch is closed when the relay "senses" that the vehicle battery voltage has reached 13.7vDC.

Battery to battery Smart Relay - Vehicle manufacturers are under pressure to make vehicles that comply with strict emmisions rules. One solution is to use a smart alternators that have their voltage output regulated by the ECU. A voltage relay doesnt work with a smart alternator so a battery to battery (or DC-DC) charger takes the highly variable voltage and stabilises it to provide a safe, controlled and fast charge for your leisure battery.

Method two- 240v Hook up charging

Having a 240v hook up is perfect for those spending time at campsites. The 240v hook up allows you to pitch up at a campsite that offers power, connect into the campsites 240v power and then use your leisure electrics to their full capacity safe in the knowledge that you will not run out of power. This method is slightly more complex in the way its fitted. The outside 240v power source is transferred into your van via your mains hook up lead. This will plug into the van via an inlet socket. These are commonly fitted to the side of the camper van but can be fitted underneath for a more stealth look.

The power will then reach the inside of the van and will arrive at the mains consumer unit. This will then distribute the power to two main places. The first being any 240v sockets in the van. These will have the same use as any household sockets, which you can use to power any 240v appliances.

The second place the power will go is to the Intelligent mains leisure battery charger. This device will monitor input and output levels and keep your leisure battery charged whilst you are connected to the campsites 240v supply. This 240v method is perfect if you are consistently using your van at campsites that can provide a 240v power source. If you are not planning on staying in these locations and fancy something a little more off grid then the next method may be better suited to you.

Method three- solar power

Using solar has its pro's and con's. Ultimately you are generating power for free and on a hot summers day you can use the solar to keep your leisure battery topped up to be able to comfortably power all your devices and appliances for the duration of your camping. This seems great apart from you cannot rely on the sun so therefore cannot rely on solar as your only source of power. We would recommend a split charge relay to be installed as well as solar.

The power is absorbed on the solar panel and is connected to a solar controller via a positive and negative cable. The solar controller monitors the energy coming from the solar panels and makes sure it leaves the controller at a safe level to charge the battery. These controllers vary in cost and spec. The top of the range controllers will give you read outs on your phone. This holds information such as current battery levels and charging status.

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Dorne Cornelius
Dorne Cornelius
Sep 13, 2023

Trying to familiarise myself with the electrics in my 2018 Caddy. A leisure battery is installed and also an inverter. I'm guessing that the inverter is there to covert any additional power coming from the engine battery, could there be any other reason for an inverter to be installed? If so, how many miles would I need to travel to keep the leisure battery active during the winter?


Hi, I have just installed a new leisure battery on my nissan NV 200. Trouble is that having connected the wires to the battery the water pump to the sink switches on. Any idea why. Really confused.


Do I need my inverter in to charge leisure batteries while engine is running or fitted to the on shore?

My power works while engine is running but no 12v while engines off. I've 240v on mains hook up but my fridge, lighting and water up are 9n the 12v system.......


I am new to caravaning and very confused about the electrics in our van we have a leisure battery fully charged and also mains electric, but I have no lights, do I have to have main electric to run the leisure battery, and any suggestions on why the lights dont work, I have changed


simon roberts
simon roberts
Jul 01, 2020

Hi just watched how to fit a split charger to a t5 could you run the cable across the bulkhead and through the grommet on the drivers side down into the drivers seatbase cheers

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