Automatically switch between vehicle and solar inputs with the REDARC 12V Relay Kit! The RK1260 Relay Kit boasts a premium, full-sealed relay perfect for the harsh Australian climate. It lets you install a BCDC in a trailer that is being towed with a vehicle equipped with a smart alternator - the ignition source is triggered and the vehicle starts and stops charging. The kit comes with everything you need, including a complete instruction sheet.