Display voltage levels of your Main and Aux battery. Background changes color to visually show your battery status at a glance: Green = both batteries are fully charged, and they are connected; Yellow = at least 1 battery is below 12.7v, and they are disconnected; Red = at least 1 battery is below 12v. Also functions as an in-cab Boost switch to jump start the vehicle from the second battery. Background light turns off after 1 minute of inactivity. Preserves battery power, No glare while driving at night, Voltage and Status is still visible, but without the backlighting. If a battery is below 12v, screen flashes red a few times per minute. Press the screen to turn the backlight on at any time. Measures approximately one cubic inch. Compact size makes it easy to mount anywhere. Includes custom 11' wiring harness for simple, clean installation Software upgradeable for future features. Order a dual battery kit at the same time for no extra shipping charges.