The system ensures that there is always a fully charged backup battery. When the switch is in position 1, battery 1 acts as a sensing battery for the VSR relay. Battery 2, which is isolated, is charged via the relay when the engine is running and thus always remains fully charged. When the switch is in position 2, battery 2 acts as a sensing battery and battery 1 is charged via the relay when the engine is running.
The system ensures that there is always a fully charged backup battery. When the switch is in position 1, battery 1 acts as a sensing battery for the VSR relay. Battery 2, which is isolated, is charged via the relay when the engine is running and thus always remains fully charged. When the switch is in position 2, battery 2 acts as a sensing battery and battery 1 is charged via the relay when the engine is running.