Battery state of charge estimation apparatus and battery state of charge estimation method

A battery state of charge estimation apparatus that estimates a state of charge of a battery, the apparatus comprising:

• a current-passage state detection section that detects a current-passage state, the current-passage state corresponding to an accumulated amount of charging or discharging current flowing through the battery for a predetermined period of time just before passage of the current stops;
• a voltage value measurement section that measures a voltage value between both electrodes of the battery when a predetermined measurement waiting period elapses from a time when the passage of the current is stopped;
• a relationship information storage section that previously stores open circuit voltage value relationship information, the open circuit voltage value relationship information being prepared for each of a plurality of the current-passage states just before the passage of the current stops, the open circuit voltage value relationship information being about a relationship between the voltage value between both electrode of the battery when the measurement waiting period elapses from the time when the passage of the current is stopped and an open circuit voltage value of the battery;
• an open circuit voltage value estimation section that estimates the open circuit voltage value with the current-passage state detected with the current-passage state detection section, the voltage value measured with the voltage value measurement section, and the open circuit voltage value relationship information stored in the relationship information storage section;
• and
• a state of charge estimation section that estimates the state of charge of the battery in accordance with the open circuit voltage value estimated with the open circuit voltage value estimation section.

A battery state of charge estimation method for estimating a state of charge of a battery, the method comprising:

• detecting a current-passage state, the current-passage state corresponding to an accumulated amount of charging or discharging current flowing through the battery for a predetermined period of time just before passage of the current stops;
• measuring a voltage value between both electrode of the battery after the passage of the current is stopped;
• measuring an elapsed time from a time when the passage of the current stops to a time when the voltage value is measured in the voltage value measurement;
• estimating an open circuit voltage value with the current-passage state detected in the current-passage state detection, the voltage value measured in the voltage value measurement, the elapsed time measured in the elapsed time measurement, and open circuit voltage value relationship information, the open circuit voltage value relationship information being prepared for a current-passage state or each of a plurality of the current-passage states just before the passage of the current stops, the open circuit voltage value relationship information being previously stored in a storage section, the open circuit voltage value relationship information being about a relationship between transition of the voltage value between both electrodes of the battery after the passage of the current is stopped and the open circuit voltage value of the battery;
• and
• estimating the state of charge of the battery in accordance with the open circuit voltage value estimated in the open circuit voltage value estimation.