The Voltage Sensitive Relay (VSR) is rated at 12VDC, 14Amps. These relays allow 2 batteries to be charged at the same time. When the aux-battery reaches 13.7 volts, the VSR engages, allowing 2 battery banks (aux and main) to be charged simultaneously. However, should the voltage drop below 12.8 volts, the VSR disengages, separating the two batteries. This system eliminates the possibility of draining the wrong battery and protects sensitive electronic equipment powered from the main battery.