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Campervan Electrics DIY Guide – why you need a leisure battery

A simple guide to fitting a leisure battery to your campervan conversion

campervan electrics diy - leisure battery

What is a leisure battery?

A leisure battery is a 12 volt battery similar in appearance to your vehicle’s main ‘starter’ battery. However a leisure battery is designed to work in a very different way to a vehicle’s starter battery. A starter battery is designed to provide a large amount of power to the vehicle’s starter motor on demand, ie. when you turn the ignition key. That power is then replenished by the vehicle’s alternator, once the engine is running.

In contrast, a leisure battery is designed to supply a more controlled flow of power over a longer period of time. The leisure battery will be charged via the vehicle’s alternator (with the aid of a split charger). If you are connected to mains hookup on a campsite, then the battery can also be charged with the aid of a battery charger, if one is fitted to the campervan.

A leisure battery will operate most efficiently in a state of discharge and recharging, this is known as ‘deep cycling’. This process will help to keep the leisure battery in good condition. You should never leave a leisure battery uncharged. If you do, then white deposits caused by sulphation will form on the plates and terminals. If this happens then the battery will be unusable. A leisure battery should never be used until it is flat.

As you can see, a starter battery and leisure battery are designed for totally different purposes. There are now batteries on the market that are dual purpose, so they can be used to start the vehicle as well as supply auxiliary power. However, if a leisure battery doesn’t state that it’s dual purpose, do not use it as a starter battery, or use a starter battery as an auxiliary battery.


What leisure battery should I choose for my campervan?

There are three main types of leisure battery:

  • Wet, lead acid battery. The most common and cheapest type of battery. Must be securely fixed in an upright position.
  • Gel filled, liquid free battery. These are more expensive than lead acid batteries but are safer as they will not spill.
  • AGM (Absorbed Glass Mat). These type of batteries are new to the market and like Gel filled batteries, are more expensive than lead acid batteries. However they are much safer and far more environmentally friendly.

So which leisure battery should you buy? Well like a lot of things, low price usually means low quality. A cheaper and lighter weight battery can lose its charge quickly and its working life will be shorter, compared to a better quality, heavier battery. Why does the weight matter? Well a heavy battery usually means that it contains more lead because it has thicker plates. This gives the battery the ability to hold a larger charge, giving it greater capacity.

If you intend to stay on campsites with mains hook up, then a less expensive leisure battery will be fine, as it’s only really going to smooth out the 12 volt power because the camper vans onboard mains charger (if fitted) will be supplying the power source. However if you are going to rely on the leisure battery to provide all of the 12 volt auxiliary power, then a better quality/heavier, more expensive leisure battery will be required.

A leisure battery’s power is measured in Ah or amp hours. The larger the Ah the greater the battery’s capacity and the longer it will last between charges. But bigger Ah also means a bigger physical size battery.


How and where do I fit a leisure battery?

The first step is to find a suitable location for your leisure battery. If you have room under the bonnet then this is going to be a good choice for two reasons.

  1. It will be easier to do the wiring and connections as everything is going to be in close proximity to each other.
  2. It will be safer, as the battery can easily vent any gases to the outside.

If you can’t fit the leisure battery under the bonnet then find a suitable place within the camper such as under the seat. This is exactly what I did in my conversion. To prevent any gas build up, I drilled a small hole in the floor for the battery’s vent pipe. You may also want to consider housing your battery in a suitable battery boxand having a fire extinguisher fitted near by.


Check out this post that shows us fitting a split charger and leisure battery in our diy campervan conversion.


How to charge the leisure battery?

Once you have decided on a suitable location for your battery, make sure that the battery is securely attached to the vehicle. The next step is to wire up the the leisure battery in such a way that it can be charged by the vehicle’s alternator. This is done by using a smart relay or split charger.

There are different types of split chargers available, but by far the simplest solution is to use a voltage sensitive split charge relay. The biggest advantage to using this type of split charger is that it doesn’t require a connection to the vehicle’s alternator, or any modifications to the vehicle’s electrical system. Which is perfect for a first time diy auto electrician.

Fitting this kind of split charger is very simple, especially if you buy a complete kit which will include everything you need for the job. Basically all you have to do is follow the simple instructions to connect your starter battery to the leisure battery using the parts supplied in the kit.

Once the split charger has been installed, the vehicle’s starter battery will work as normal and receive charging via the alternator. In addition to this, the split charge relay will also charge the leisure battery. It does this by detecting the rise in voltage from the vehicle’s charging system whilst the engine is running. When the engine has stopped, the relay will isolate your starter battery from the leisure battery, ensuring that there will always be enough charge in the starter battery to start the vehicle.


What leisure battery and split charger kit combo do I buy?

To make it easier for you to decide, I have chosen four leisure battery and split charge relay kit combinations which are currently available on Amazon.


3mtr Split Charge Relay Kit – 140amp 

This kit comes with 3 metres of cables. The leisure battery will need to be within 3 metres of the starter battery, remembering to allow for the twists and turns of routing the cables.

Suitable for all vehicles: does not require an ignition feed or any additional wiring.

Suitable for charging all 75AH to 220AH leisure batteries.

More information and best prices for this kit 

Suitable leisure batteries for this kit:

All batteries come with free delivery.

75AH leisure battery 

100AH leisure battery 

110AH leisure battery 

120AH leisure battery 

130AH leisure battery 


4mtr Split Charge Relay Kit – 140amp 

This kit comes with 4 metres of cables. The leisure battery will need to be within 4 metres of the starter battery, remembering to allow for the twists and turns of routing the cables.

Suitable for all vehicles: does not require an ignition feed or any additional wiring

Suitable for charging all 75AH to 220AH leisure batteries.

More information and best prices for this kit 

Suitable leisure battery for this kit:

All batteries come with free delivery.

75AH leisure battery 

100AH leisure battery 

110AH leisure battery 

120AH leisure battery 

130AH leisure battery 


5mtr Split Charge Relay kit – 140amp

This kit comes with 5 metres of cables. The leisure battery will need to be within 5 metres of the starter battery, remembering to allow for the twists and turns of routing the cables.

Suitable for all vehicles: does not require an ignition feed or any additional wiring

Suitable for charging all 85AH and 220AH leisure batteries

More information and best prices for this kit 

Suitable leisure battery for this kit:

All batteries come with free delivery.

85AH leisure battery 

100AH leisure battery 

110AH leisure battery 

120AH leisure battery 

130AH leisure battery 


8mtr Split Charge Relay Kit – 140amp

This kit comes with 8 metres of cables. The leisure battery will need to be within 8 metres of the starter battery, remembering to allow for the twists and turns of routing the cables.

Suitable for all vehicles: does not require an ignition feed or any additional wiring

Suitable for charging up to 125AH leisure batteries

More information and best prices for this kit 

Suitable leisure battery for this kit:

All batteries come with free delivery.

75AH leisure battery 

100AH leisure battery 

110AH leisure battery 

120AH leisure battery 


How do I connect my 12 volt items to the leisure battery?

You will need to connect a fuse box to your leisure battery, you can then connect your 12 volt items to the leisure battery via the fuse box. If you were to use a 6 way fuse box for instance, you could then connect 6 items to the leisure battery and each connection/item will have its own fuse. If you use a 10 way fuse box, then you could connect 10 items to the leisure battery or 8 items and have two spare connections for any future additions. Connecting a fuse box to the leisure battery is a simple process. Unless the fuse box has a negative connection, you just connect a positive feed from the leisure battery to the fuse box.

Here are 4 fuse boxes available on Amazon:

4 way 12v blade fuse box

6 way 12v blade fuse box

8 way 12v blade fuse box

10 way 12v blade fuse box

12 way 12v blade fuse box

One final addition to your leisure battery installation will be a switch panel. This will allow you to turn on and off each of your 12v items that are connected to the fuse box. The are many styles of switch panels available. The switch panel below is a particularly good example as it also incorporates two USB charging sockets and a voltmeter.


You may also be interested in this article – Fitting a solar panel to your Campervan

 

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