Dual Battery System
Also known as: house battery setup, second battery system, auxiliary battery, split charge system
A second, isolated leisure battery dedicated to running a van's living systems (fridge, lights, devices) without draining the engine's starter battery.
A dual battery system keeps your starter battery untouched so you never wake up to a van that won't start.
The leisure (house) battery is charged while driving — on a modern Euro 6 van that means a DC-DC charger rather than a simple voltage-sensitive relay, because smart alternators vary their voltage and a plain split charge relay no longer charges reliably. Solar tops it up when parked. A DC-DC charger or smart relay separates the two circuits so the loads in your living space can never flatten the cranking battery.
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Reviewed 2026-06-26 · by Maximus