What is a Leisure Battery?
The separate battery that runs your lights, water pump and fridge — without you ever waking up to a dead engine.
Simplified animation — not to scale.
In plain English
Every campervan has two batteries: the starter battery (for the engine) and the leisure battery (for everything in the back — lights, USB sockets, the water pump, the fridge's 12V mode). They're kept apart so that a night of charging your phone and running the lights never leaves you stranded in a car park.
"Think of it as a separate phone battery just for the house bit of your van — the engine has its own, and never has to share."
How it works
A charge relay or DC-DC charger tops the leisure battery up from the engine while you drive, and a solar panel or mains hook-up can do the same while you're parked. A control panel or app then shows you roughly how full it is.
Signs of trouble
- ⚠Lights dimming noticeably in the evening
- ⚠The water pump slowing to a dribble
- ⚠The fridge switching itself off overnight
- ⚠A battery monitor reading consistently low even after driving
£120 – £450 fitted, depending on capacity and whether it's AGM or lithium (LiFePO4).
Ballpark only — depends on your van, converter and local labour rates.