12V electrical system in your camper van: getting started
The electrical system is one of the most complex parts of a camper van conversion, but also one of the most important. A well-designed 12V system is safe, reliable and gives you the freedom to go off-grid. In this guide we take you step by step through the basics.
Plan your electrical installation
The components of a 12V system
A complete 12V camper van system consists of these components:
1. Battery bank: stores the energy. Lithium (LiFePO4) or AGM.
2. Charge controller (MPPT): converts solar panel voltage to the correct charging voltage.
3. B2B charger: charges the leisure battery via the starter battery while driving.
4. Shore power charger: charges the battery when on a campsite.
5. Inverter: converts 12V DC to 230V AC.
6. Fuse box: distributes and protects all outgoing circuits.
7. Switches: for lighting, water pump, etc.
8. Wiring: connects everything with the correct gauge.
The basic setup: how to connect everything
The core of your system is the battery. All charging sources (solar panels via MPPT, B2B charger, shore power charger) come together on the positive and negative terminals of the battery.
From the battery, a thick cable goes to the fuse box. From there, separate circuits go to your consumers, each protected by its own fuse.
The connection:
Battery (+) → main fuse → busbar (+) → fuse box → consumers
Battery (-) → busbar (-) → ground connection consumers
Keep the cables between battery and fuse box as short as possible (max 1-1.5 meters) and use the correct gauge. A cable that is too thin is the biggest safety risk.
Fuses: why every cable needs one
A fuse protects the cable, not the device. If a short circuit occurs or the device draws too much current, the fuse blows before the cable overheats.
Choose the fuse based on the maximum current rating of the cable:
• 1.5 mm² cable: max 10A fuse
• 2.5 mm² cable: max 16A fuse
• 4 mm² cable: max 21A fuse
• 6 mm² cable: max 28A fuse
For the main cable between battery and fuse box, use an ANL or MEGA fuse (e.g. 100-200A depending on cable gauge).
Always place the fuse as close as possible to the positive terminal of the battery — if a short circuit occurs in the cable, it is immediately protected.
Common electrical mistakes in camper vans
The five most common mistakes in 12V installations:
1. No fuse on the battery cable: if this cable short-circuits, the full battery current (hundreds of amps) can flow through the cable. This causes fire.
2. Cables too thin: especially cables to the inverter are often underestimated. A 1000W inverter draws 85A+ at 12V — you need 25-35 mm² cable.
3. Poor connections: loose lugs or badly crimped connections cause resistance, heat and eventually fire. Use a proper crimping tool and check every connection.
4. No main disconnect switch: you must be able to fully shut down the system in emergencies. Install a main switch on the battery cable.
5. Chassis ground: in a camper van you should use a return cable, not the chassis as ground. The chassis is not designed for the currents of a living system.
Plan your electrical installation
Use our free tools to calculate cables, fuses, batteries and wiring for a safe installation.
Frequently asked questions
- How do I start with the 12V system in my camper van?
- Start by calculating your power consumption. Make a list of all devices and their consumption. Then choose your battery capacity, solar panels and charge controller. Draw a diagram before you start wiring.
- Do I need an inverter in my camper van?
- Only if you want to use 230V appliances (laptop charger, hair dryer, coffee machine). Many devices also work on 12V or USB. An inverter also consumes power itself, so only use it when truly needed.
- Can I install the 12V system myself?
- Yes, many camper van converters do this themselves. Use the correct wire gauges, protect every cable with a fuse and make a clear wiring diagram. If in doubt, have it checked by a professional.