12v Campervan Electrics for your Campervan

These days, most of the electrical appliances you will run in your campervan conversion will be powered by a 12v leisure battery. Modern 12v appliances are low in power draw and there are significant advantages to not requiring 240v connection. Solar charging in particular, plays a large role in maintaining power when off grid for extended periods of time. Some of the 12v appliances you may plan to fit into your van are below;

• 12v compressor fridge (probably the most important 12v appliance – super efficient and performs well off-grid)
• 12v lighting – over 10 times as efficient as halogen equivalent
• 12v water pump
• 12v water heater (great for off grid travels when paired with solar)
• 12v TV – most 12v tv’s now come with built in Freeview and compact aerials (no need for bulky satellites).
• 12v socket outlets  – these will let you run portable 2v appliances such as a coolbox or fan.
• 12v USB sockets
• Diesel or gas heating air blown heaters (12v power is required for the fan)

When planning and installing your 12v electrics into your campervan, it is best to break down the required elements into separate wiring looms with separate functions. This will create more order in your planning and avoid you being overwhelmed with too many cables.

It is important to remember that 12v battery charging may require a range of cable sizes and specification, for example an 18 amp 240v battery charger may require a 3-4mm cross section cable, while a 140 amp split charge system will run at least 16mm cross section cable. All cable sizes should use correspondingly matched fuse sizes.

Your 12v planning can be broken down into the following looms:

• 12v  battery split charging
• 12v solar charging
• 240v-12v battery charging
• 12v fuse board to appliances.

12v Split Charging

A 12v split charge wiring loom is almost always fitted to modern campervans and motorhomes. It facilitates the charging of the leisure battery while the engine is moving. One of the main features allows the batteries to be separated once the engine is no longer running. This ensures that the starter battery is always protected and isn’t flattened through use of leisure facilities such as your fridge and lights.

It should be noted that even though some of the power management units state they have built in split charge capability, these are almost always inadequate. We would recommend that you always run a separate split charge loom that is independent to the power management unit.

There are two distinct types of split charging used:

VSR (Voltage Sensing Relay) (power rating 50-140 amps)

These are used on older models of vans (Euro 5 engine and earlier) that don’t have smart alternators. The basic switching relay allows for a powerful charge to be delivered of 20-80 amps. This type of charging unit is suitable for lead acid, AGM and gel batteries but is not suitable for lithium ion batteries.

These split charge kits are often available as pre-wired kits to make installation straight forward.

B2B (Battery to Battery Chargers) (power rating 20-50 amps)

The more sophisticated electrics on these types of chargers allow them to deal with the variable output from modern smart alternators. B2B chargers can also be used on older euro 5 engines, some models are available as duel input allowing both solar and split charging from one unit.

Solar charging

Modern solar panels are affordable, reliable and quite straight forward to install.  The addition of a small solar installation (around 100 watts for a small van and 200-400 for a medium to large van) will make a huge difference to the versatility of your campervan conversion.

As an example, a 100 watt panel with 100 amp battery will allow you to keep your fridge, lights, and general appliances running full time throughout the spring and summer months.

Without a solar panel the battery will require recharging every 2-3 days.

There are different panel types and solar regulators available but a good rule of thumb is to stick with monocrystalline panels and MPPT solar regulators. MPPT regulators are safer and will not over charge your batteries.

240v to 12v battery charging

Recharging your leisure battery from the mains power supply can be convenient and particularly necessary if you don’t have a solar installation on your van.

Electric hook-up connections on camp sites are readily available and mains hook-up on your van will also allow you to connect at home to recharge your batteries before you head off on your travels.

If you are running a power management unit then your control panel will often allow you to run all of your 12v appliances from the main supply, as well as diverting a charge to your leisure battery.

A small generator can also be used as a power source for the 240v connection allowing recharging  and running of the 12v system when off grid. You should aim to have a 240v charger of no less than 12amps output (most are 18 amps and above), otherwise it will take too long to recharge your system.

12v Fuse board to appliances

Once you have established your leisure battery installation with adequate recharging capability then the last stage of your 12v installation is the connection of 12v appliances. The number of 12v connections required will determined what type of fuse or fuse board that is used. If you have a power management system  such as the Sargent Ec155  then you will have built in fuses to run your various appliances off. On more basic installations you may only have one or two 12v appliances and these can be run off individual fuse holders.

It is important that the correct cable size is used for the appliances you plan to install. Many of the 12v output such as led lighting, pump, TV, fans and usb ports can be wired with 1.5mm trim core cable. However, items such as your fridge will require a larger cable size of 4-6mm cross section to avoid voltage drop.