Caravan wiring looks complicated but it comes down to two separate systems doing two different jobs. Once that clicks, the rest makes sense. Our listings tag what each van has, usually some mix of 12V, 240V and solar.
Two systems, side by side
12V is the caravan's own low voltage system, run from a battery on board. It powers the things you need everywhere: lights, the water pump, the heating controls, the fridge in 12V mode, USB sockets and the motor mover. It works whether or not you are plugged into anything.
240V is ordinary household mains, which only exists in the van when you plug the lead into a power post at a campground. It powers the three-pin sockets, the jug, a hair dryer, an electric heater, and it usually runs a charger that tops up the 12V battery while you are connected.
The simple rule: 12V runs the van, 240V runs the appliances.
The battery
Everything about free camping comes back to the battery.
- Lead acid or AGM batteries are the traditional choice. They are cheaper, heavier, and you should only use about half their stated capacity before recharging, or you shorten their life badly.
- Lithium (LiFePO4) batteries cost more up front, weigh much less, and you can use nearly all of their capacity. They also charge faster. Most new installs are going this way.
Battery capacity is given in amp hours (Ah). A 100 Ah lead acid battery gives you roughly 50 Ah of usable power. Lights, pump and phone charging for two people is often 20 to 40 Ah a day, so that is around a night and a half before it needs a charge. A 12V fridge running all day can easily double that draw.
Batteries are also the most common tired item in a used van. Ask how old it is. A battery is a normal replacement item, not a fault, but it is worth knowing.
Charging it back up
There are three ways to put power back in:
- Solar. Panels on the roof, working quietly all day. Best for staying put somewhere with no power. Output drops a long way in winter and under cloud.
- Mains charger. Plugged in at a powered site, this refills the battery fastest and most reliably.
- From the tow vehicle. The car charges the caravan battery a little while you drive. A DC to DC charger does this properly, and is worth having if you move on most days.
Inverters
An inverter turns 12V battery power into 240V so you can use a normal plug when you are not connected to mains.
It is genuinely useful for small things: charging a laptop, running a TV. It is not a substitute for a power post. Anything that makes heat (a jug, a toaster, a hair dryer, an electric heater) pulls so much current that it will empty a typical battery in minutes. If a van has an inverter, take it as a convenience, not as a way to live off grid with mains appliances.
Powered sites
Plugging in at a campground gives you 240V, but there is a limit at the post, often 10 amps, sometimes less. Rough guide, one 2 kW appliance at a time. Run the jug and a fan heater together and you will trip the breaker, usually for the whole row of sites.
You need a proper heavy duty caravan lead, not a household extension cord, and the van's mains system should have a residual current device (an RCD safety switch) in it.
What to check when you inspect a van
- Turn on every light and run the water pump.
- Plug in to mains and check the sockets work and the charger comes on.
- Ask the age of the battery and whether it has been left flat.
- Ask when the electrical work was last checked. Any 240V work in a caravan is a job for a registered electrician, and there should be a current electrical warrant of fitness for the mains system.
If any of this is unclear on a van you are looking at, ask us. We would rather walk you around the switch panel in person than have you guess.