What Is a Split Charge Relay and When to Use It

A split charge relay is a simple, older-style system that connects your starter battery to your leisure battery whenever the engine is running. It lets power flow straight from the alternator to your leisure battery, keeping it topped up.

These relays work best with older vehicles (usually pre-2015) and standard wet lead-acid batteries. They’re straightforward to fit but don’t regulate the voltage coming from the alternator.

This also makes split charge relays unsuitable for lithium batteries. Lithium requires a controlled, specific charging profile, and without regulation, charging can be inefficient and may place unnecessary strain on both the battery and the alternator. For modern vehicles and lithium setups, a DC-DC charger is the smarter, safer choice.