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Camper van electrical systems, explained

A plain guide to the parts of a van or RV electrical system and the decisions that shape it.

For the diagram of how power flows, see How a van power system works. This page covers what to decide when planning one.

1. Two batteries, two jobs

The starter battery starts the engine. The house (auxiliary) battery runs everything in the living space. Keeping them separate means using the fridge overnight cannot leave you unable to start the van.

2. Pick a system voltage

Most vans use 12V because vehicle accessories, fridges, fans and lights are built for it. Some larger systems use 24V or 48V, which carries the same power at lower current, so it can use thinner wire. See Power basics for why watts = volts × amps.

3. Choose the house battery chemistry

LiFePO4 is lighter and lets you use more of its rated capacity, but it costs more upfront and cannot be charged below freezing without heating. AGM costs less and tolerates cold charging at reduced current, but it is heavier and should only be discharged about halfway for good life. Full comparison: Battery types explained.

4. Plan the charging sources

5. Decide how much AC you need

An inverter turns battery DC into 120V AC. Size it to the largest AC load you will run at once, and remember it draws from the battery while it runs. Many builds keep fridges, fans and lights on 12V and use AC only where needed.

6. Protect every circuit

Fuse or breaker every positive wire near its source, size wires for the current and length, and follow each maker's manual. If you are not sure, have a qualified installer do or check the work.

General information, not professional electrical advice.

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