Allows two batteries to automatically charge at the same time and then isolates the batteries, ensuring the starting battery is always charged. Automatically engages or disengages the circuit at pre-set voltages, eliminating the possibility of discharging the primary starting battery. Cut-in voltage: 13.3V. Cut-out voltage: 12.8V. Surge protected. An LED indicator alerts the user when the unit is engaged. Constructed of machined brass with a weatherproof injection molded nylon housing and silver tipped contacts. Includes two #8 RH fasteners. IP65 rating. Amps 140 Volts 12 Size 2-5/8" x 2-5/8" x 2"