Dual Battery Isolators / Voltage Sensitive Relays have been specifically designed for a wide variety of 12V applications. Dual Battery lsolators sense the input voltage generatedand automatically connect/disconnect the appliance or circuit at pre-set voltages, eliminating the possibility of discharging the primary starting battery. Constructed with a weatherproof body (IP65) and durable silver tipped contacts. Dual Battery Isolators also feature surge protection and a L.E.D indicator designed to alert the user when the unit is engaged. Dual Battery Isolators are ideal for dual battery set-ups asthey enable two batteries to be charged at the same timeand then isolates the batteries from each other when the vehicle is turned off,ensuring your starting battery isalways charged and ready to go.