If you have a voltmeter included in your leisure battery bank monitoring system, the reading will show an increased voltage level when the relay is on and charging the leisure batteries probably around 13.9v (ish). If you have a solar array connected, a voltage increase is less obvious because the solar charge controller maybe providing a charge at the same time. In this case you might see only a slight increase in the voltage level. Without battery monitoring, follow these steps: - Switch off engine - Disconnect the split charge relay output cable from the leisure battery - Using a multimeter, measure the voltage at the end of that cable (it should be zero) - Put the cable is a safe place so it isn’t touching anything - rest the cable on something non conductive so the end of it isn’t touching anything - Turn on the engine - Using a multimeter, measure the voltage at the end of that cable (it should be about 13.9v) - Switch off the engine & reconnect the cable to the battery bank