Leisure Battery Wiring Campervan
This guide explains how to wire a leisure battery in a campervan safely using a DC-DC charger or split charge relay. Learn correct fuse placement, cable sizing basics and typical UK installation layouts.
Campervan leisure battery wiring at a glance
| Component | Purpose |
|---|---|
| Starter battery | Provides charging power from alternator |
| Main fuse (starter side) | Protects charging cable near battery |
| DC-DC charger or split charge relay | Controls charging between batteries |
| Main fuse (leisure side) | Protects cable near leisure battery |
| Leisure battery | Powers campervan appliances |
Simple leisure battery wiring diagram campervan
A typical campervan leisure battery installation follows this charging path:
Starter battery → fuse → DC-DC charger → fuse → leisure battery
How a leisure battery charges while driving
When the engine runs, the alternator produces power which flows through a protected charging cable into the DC-DC charger or split charge relay.
- Starter battery provides alternator power
- Fuse protects the cable
- DC-DC charger regulates charging voltage
- Leisure battery stores energy for appliances
This keeps your starter battery protected while charging the living-area electrical system safely.
Where to place fuses when wiring a leisure battery
Fuse placement is one of the most important safety steps in a dual battery system.
| Fuse Location | Purpose |
|---|---|
| Near starter battery | Protects main charging cable |
| Near leisure battery | Protects return cable path |
| Between leisure battery and fuse box | Protects appliance circuits |
What cable size connects starter battery to leisure battery?
Cable size depends mainly on charger current and cable length.
| DC-DC Charger Size | Typical Cable Size |
|---|---|
| 20A charger | 10mm² |
| 30A charger | 16mm² |
| 40A charger | 25mm² |
| 50A charger | 25mm² to 35mm² |
See full sizing guide here: Alternator to Leisure Battery Cable Size Guide
Rear leisure battery install example
Many campervans install the leisure battery in the rear of the vehicle. This increases cable length and makes correct cable sizing more important.
Front starter battery → long cable run → DC-DC charger → rear leisure battery
DC-DC charger vs split charge relay wiring
| System Type | Best For |
|---|---|
| Split charge relay | Older vehicles without smart alternator |
| DC-DC charger | Modern vans with smart alternator |
Most Euro 5 and Euro 6 vehicles require a DC-DC charger for reliable leisure battery charging.
Common campervan leisure battery wiring mistakes
- Using cable that is too small
- Missing fuse protection near batteries
- Poor grounding connections
- Incorrect charger sizing
- Routing cables without protection
Helpful calculators for leisure battery wiring
Related campervan wiring guides
Plan your leisure battery wiring safely
Correct cable sizing and fuse protection make campervan charging systems safer and more reliable.
Open Electrical CalculatorsElectrical installation safety notice
This guide and the associated calculators are provided for general educational purposes only. They show typical wiring layouts and estimation methods commonly used in UK 12V campervan electrical systems.
Every campervan installation is different. Cable sizing, fuse selection, charger type, battery chemistry and routing should always be checked against manufacturer specifications and the requirements of your specific vehicle.
Where high-current battery systems, DC-DC chargers, inverters or 230V mains hook-up equipment are involved, installation should be completed or inspected by a suitably qualified installer.