Backup Battery Control Module and Backup Battery Control System

A backup battery control module configured to supply electric power from a backup battery to a load when electric power supply from a main battery to the load is cut off. The backup battery control module is configured to: measure an open circuit voltage of the backup battery in a state in which an ignition switch is off; derive, based on a measured open circuit voltage, an already charged rate of the backup battery; measure an internal resistance of the backup battery in a state in which the ignition switch is off; derive a deterioration degree of the backup battery based on a measured internal resistance; derive a target charging rate based on the deterioration degree; and charge the backup battery until the target charging rate is reached in a case in which it is determined that the already charged rate is smaller than the target charging rate.