How a campervan electrical system works

The electrics are usually the part people put off. They look complicated, and there's a lot of jargon. But underneath it, every leisure electrical system, whether campervan, caravan or motorhome, does the same three things:

1. Stores power in a leisure battery
2. Charges that battery from one or more sources
3. Uses that power to run your appliances

That's it. All the choices you'll face sit inside those three jobs, not outside them.

First: your van has two electrical systems

The starter battery does one job: a short, hard burst to fire the engine, then straight back up to full from the alternator.

The leisure battery does the opposite. Slow discharge over days, powering appliances, recharged over and over. Everything in the living area runs from the leisure battery. Keep the two apart, because most of the problems we see start with them being mixed up.

What every system needs

Three components, minimum:

• A leisure battery, where the power lives
• A fuse board / distribution unit, which protects everything and splits the power out to your lights, sockets and appliances
• A way to charge it

Each charging method does a different job, and the best systems combine at least two, ideally all three:

• Mains hookup: the fastest and most reliable way to fully charge before a trip or while on a serviced campsite
• DC-DC charger: tops up the battery while you are driving
• Solar: offsets daily use while you are stationary, extending off-grid time without any effort

Add an inverter only if you need to run 230v mains appliances off the battery.

Two ways to put it together

An all-in-one power management system does mains charging, 12v distribution, fusing and battery monitoring in a single unit. CBE and Sargent are the two names you'll come across. Sargent in particular is factory-fitted in a lot of UK caravans and motorhomes, so if you're replacing a failed unit, there's a good chance you already have one, and like-for-like is almost always the cheapest, simplest route.

Worth knowing: all-in-ones usually cover mains charging and distribution, may not be lithium compatible, and often don't include DC-DC or solar. Those get added alongside as separate components later.

A component-based system means choosing each part yourself: mains charger, DC-DC charger, solar controller, battery monitor, distribution. More planning, more wiring, but complete control and room to grow. Victron is the brand most associated with this. Modular, everything talks to everything else, and you can see and control the lot from your phone via the VictronConnect app.

Which one?

• Replacing a unit in an existing caravan or motorhome → like-for-like CBE or Sargent
• New build wanting a clean, ready-made solution → CBE or Sargent
• Campervan self-build, lithium, solar, or a system you'll expand over time → Victron

Where to start

Before you buy anything, answer these three:

1. What do you want to run?
2. How long between charges?
3. How will you recharge? Hookup, driving, sun, or a mix.

Those answers decide your battery size, your charging setup, and whether you need an inverter. Everything else follows.