Stinger SGP38 RELAY 80AMP & BATT ISOHigh current relays are the most reliable and efficient way to add secondary batteries to your system. Using an isolator when adding a second battery will keep the batteries from discharging each other and allow you to run accessories from the secondary battery without draining the primary battery for safe starting. After the Stinger 80 Amp Relay and Isolator is installed per instructions, the 2 batteries are automatically connected when the vehicle