It allows to charge an auxiliary battery of the vehicle with the maximum security, preventing the discharge of the main battery. With LED indication for easy state reading. Indicates the charge level of both batteries through tri-color indicator lights. After the relay is enabled, it will only be disabled 120 seconds later. The relay is actuated when the primary battery voltage is above 13.3 V, and disabled when it is below 12.8 V. It has a button that allows to enable the relay in forced mode.