Ensures that the on-board battery is disconnected from the starter battery when the engine is stopped. This prevents the starter battery from being discharged via the on-board consumers, which means that there is no longer enough power available to start the engine.
When the engine is then started and the alternator delivers charging current, the isolating relay ensures that the on-board battery is recharged in parallel via the alternator.
An extinguishing diode to suppress inductive voltages is integrated.