Secondary battery status estimation device and status estimation method

A secondary battery status estimation device comprising:

• a sensor unit configured to detect a terminal voltage and a charge-discharge current of a secondary battery;
• and
• an internal resistance calculator configured to calculate a direct current internal resistance of the secondary battery based on the terminal voltage and the charge-discharge current detected by the sensor unit,
• wherein the internal resistance calculator calculates the direct current internal resistance based on the terminal voltage and the charge-discharge current that have been detected by the sensor unit, in a stable period and in a high-current output period,
• the stable period is before starting a driving source for driving a vehicle and the terminal voltage and the charge-discharge current of the secondary battery fall within a predetermined fluctuation range in the stable period, and
• when starting the driving source, electric power for starting the driving source is output from the secondary battery and the terminal voltage of the secondary battery is brought to substantially minimum in the high-current output period.