Redundant power supply control device and control method

A redundant power supply control device that controls a sub-battery that is able to back up a main battery, the redundant power supply control device comprising:

• an acquisition unit that acquires a voltage value and a current value of the sub-battery;
• an estimation unit that estimates a storage rate of the sub-battery by a current integration method;
• and
• a determination unit that determines whether the sub-battery is able to be backed up, wherein the determination unit
• calculates a first resistance value that is an internal resistance value of the sub-battery estimated based on a measured voltage value and a measured current value acquired by the acquisition unit,
• calculates a second resistance value that is an internal resistance value of the sub-battery estimated based on an estimated voltage value derived from the storage rate estimated by the estimation unit and the measured current value, and
• determines whether the sub-battery is able to be backed up based on a larger resistance value of the first resistance value and the second resistance value.