INSTRUCTIONS: 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. FEATURES: Designed for dual battery systems- Suitable for most 12V charging systems Surge protection Easy to install Automatically sensing voltage level of main battery Cut In Voltage: 13.3V Cut Out voltage: 12.8V Emergency Charge Function Package Includes: 1x Split Charge Relay with hardware assembly kits Notes:The black wire in the VSR must be connected to the ground/negative of battery, the yellow wire in the VSR is for the emergency charge(force charging from the start battery to leisure battery regardless the voltage of start battery is higher or lower than 12.8V), you can also just leave it alone if you don't want the emergency charge function.