Campervan 12V Wiring Diagrams

A deep dive an the options you have for your 12V system.


Overview Of A 12V Campervan Electrical System

To a van-building newbie, the electrical system can be one of your conversion’s more painful, drawn-out and head-scratching parts. But, here at Vunked HQ, we believe electrical systems don’t need to be complicated. So, we will unpack a typical 12V electrical system, present a few campervan 12V wiring diagrams and discuss your options for how to build your system.

What can you power with 12V

We’re dealing mainly with the consumer side of our system, from the batteries to the lights and other appliances. The generating side of our system, from the solar panels and DC-DC charger to the batteries, is dealt with in a couple of separate blogs. Check out our solar panel 101 and DC-DC installation blogs for more information on those parts of your system.

If you want to, you can skip to our campervan 12V wiring diagrams and examine your options for designing your 12V system.

Introduction to 12V Electrics

The overwhelming odds are that your campervan will be based on a 12V electrical system. This is because 12V has become the standard for small-scale, off-grid power such as campervans, caravans and boats. This is the same as your car or van starter battery, meaning there are many options for technologies, capacities and manufacturers. We discuss different types of 12V batteries in a separate blog.

A Note On 24V and 48V Electrics

We’re starting to see some large electrical systems being run on 24V. The higher voltage allows a smaller current flow. It stops cables from getting too large and inflexible for use in a campervan. We’re talking about some hefty systems to make 24V (or even 48V) useful. Think induction hobs and electric heating for a start. 

These systems are still pretty rare (especially in the UK), so we’ll stick with 12V for now, covering almost all van converters.

What Does a 12V System Include?

The majority of the appliances in our campervan will likely run on 12V. Everything that you consider “essential” in your campervan will be run off the 12V system, including:

Common 12V appliances

A separate inverter system will power typical household appliances (which run on 230V). We’ve already covered 230V extensively in another blog, so we’ll forget about this.

12V Cabling

Most of the above appliances will require similar cable sizes, but a few exceptions exist. For example, our lights, roof fan, water pump, control panel, battery and gas monitors, USB chargers, combi-boiler and gas or diesel heaters can all be fed by 2mm2 cable – make sure you have plenty of this.

Our fridge will likely require a larger cable due to its higher power consumption. The requirements will vary depending on which fridge you opt for, but 6mm2 is standard.

12V fridge

12V Wiring Diagram

Once you’ve decided where your appliances will be, you’ll have to draw up a wiring diagram and make sure you’re happy with where your cable run will be. Your 12V system is a single, large parallel circuit, with all branches stemming from your 12V fusebox. 

One exception to this is your lighting circuit, which will likely have its own branches if you want all lights to share a single switch.

Campervan 12V Wiring Diagrams

Between your batteries and these appliances, you’ll also find a fusebox and switches for all these appliances, maybe even a battery protect and a switching or control panel. There are several ways to connect your 12V system, so we’ll run through each scenario below:

  1. Fuse box with isolator switch
  2. Fuse box with BatteryProtect
  3. Fuse box with switch panel

Fuse Box with Isolator Switch - 12V Wiring Diagram Included

Our most basic 12V arrangement features a fuse box and an isolator switch, connected up as shown in the diagram below. The positive cable arrives at the isolator switch from our batteries before continuing to the 12V fuse box. The negative comes directly from the battery feed directly into the 12V fusebox. We always recommend using an isolator switch to isolate the fuse box safely. That’s why we include one in every 12V system we sell.

Why Should I Use a 12V Isolator Switch?

An isolator switch is a must-have on your 12V campervan electrical system. It lets you turn off the 12V appliances so they are not drawing any power so you can safely work on your electrics. 

12V with Isolator Switch

Whats Included

Sourcing all the components to assemble your 12V system can be a pain. Luckily, our basic 12V system includes everything you need to install it, including:

  • 12-way fusebox
  • MIDI fuse holder with 40A fuse
  • Victron Energy isolation switch
  • 2m of 16mm2 red and black cable
  • All necessary lugs and heat shrink
  • 24 fuses (various ratings)

Fuse Box With Battery Protect - 12V Wiring Diagram Included

Next up, we have the fuse box with battery protect. The battery protect ads and extra layer oof protection to both your appliances and battery. 

Why Should I Use a Battery Protect?

The Victron Energy BatteryProtect adds extra protection to your campervan electrical system. Outlined as:

  • Battery Protection – The BatteryProtect will monitor the voltage running through it and shut off the current flow when the voltage drops too low. This protects your battery from over-discharge, which is harmful to most batteries. 
  • Correct Current Flow – The BatteryProtect is uni-directional, meaning the current can only flow one way. 
12V with Battery Protect

Fuse Box With Switch Panel - 12V Wiring Diagram Included

The final option is to add a switch panel to your 12 fuse box. The switch panel can be added alongside an Isolation Switch or BatteryProtect

Why Should I Use a Switch Panel?

Adding a switch panel to your 12V campervan electrics gives you a few benefits:

  • More 12V Circuits – The Switch Pannel will connect to one terminal on your fuse box, providing up to six extra circuits. However, make sure you use the appropriate wire and fuse sizes, as all those extra loads will be travelling between the one cable connecting the fuse box to the switch panel.
  • Easily Control Appliances – Host the switch panel inside your campervan to turn all your connected 12V appliances on and off conveniently.
12V with Switch Panel

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