Battery pack and battery capacity calculating method

A battery capacity calculating method, comprising:

• judging whether a past charging current of a secondary battery is stored in a storage section when the secondary battery is started to be charged, and in a state where the past charging current is not stored, measuring the charging current of the secondary battery and storing the charging current and a charge capacity obtained when the charge is started;
• calculating the charge capacity of the secondary battery by integrating, in each certain cycle, the charging current that has flown in a predetermined cycle;
• calculating a current change amount that is a change amount of the charging current with respect to the charge capacity;
• judging whether the secondary battery is being charged with one of a constant voltage and a constant current, when the secondary battery is being charged with the constant voltage, calculating a remaining charge capacity based on the charging current measured and the current change amount, calculating an adjustment value from a ratio of a battery capacity necessary to reach the full charge of the secondary battery, the battery capacity being calculated using the change amount of the charging current with respect to the battery capacity, to a difference between the battery capacity of the secondary battery in a fully charged state and the battery capacity of the secondary battery at that time, and when the secondary battery is being charged with the constant current, setting the adjustment value to 1;
• calculating a battery capacity of the secondary battery by integrating, in each certain cycle, an adjustment charging current value calculated using a product of the charging current that has flown in a predetermined cycle and the adjustment value;
• calculating a degree of deterioration of the secondary battery from a ratio of the change amount of the charging current with respect to the charge capacity and the change amount of the charging current with respect to the charge capacity at a time when the secondary battery is started to be used, storing the calculated degree of deterioration in the storage section, and making an update;
• and
• calculating the full charge capacity by a product of an initial full charge capacity that has been stored in the storage section in advance and the degree of deterioration, storing the calculated full charge capacity in the storage section, and making an update in a case where the secondary battery is detected to be fully charged.