The battery sensor measures battery voltage, sensor temperature, and charge/discharge currents. According to these readings, battery fluid temperature, internal resistance, and state of charge are sent as signals from the battery to the gauge control module. After the vehicle is turned to the OFF (LOCK) mode, the battery sensor observes the charge state of the battery. When a designated threshold is reached, a signal is sent through the LIN circuit interface and displayed on the gauge control module. As a result, the battery sensor can alert the driver of over discharge when in the ACCESSORY mode or automatically switch off interior lights through the MICU.