About this item: [ Compatibility ] - Battery isolators are small and fit almost anywhere, for , UTV, Boats, RVs, Marine, Trucks, Caravans [ Working Voltage ] -- The Voltage Sensitive Relay (VSR) cuts in at 13.3 volts and cuts out at 12.8 volts to ensure your main battery is always charged and ready to run your vehicle [ Function ] -- With the engine running, the VSR cuts in when the starter battery reaches 13.3 volts and the LED indicator lights up. This means the two batteries are now linked and the system is working. Once you turn off your vehicle, the system will disengage both batteries when it reaches 12.8 volts, leaving your primary battery safe to restart [Important Note]--When connecting accessories to your second battery, make sure they are fused within 0.98 FT Product Parameters: Type: 12V Voltage Sensitive Relay Continuous Current: 80-100A Instantaneous Current: 125A Current Draw - Load: 240mA Current Draw - Standby: 8mA Detach Delay: 5-10 seconds Recommended Fuse: 80 Amp