Patent ID: 10553913

Abstract:
A control is performed to set a current value exceeding a nominal capacity of the secondary battery to first charging current to charge the secondary battery, compare the measured voltage of the secondary battery with first threshold voltage that is lower than a prescribed charging voltage while performing constant current charging with the set first charging current, decrease the first charging current to be second charging current when the measured voltage is higher than the first threshold voltage, and increase the first threshold voltage by a predetermined amount to be second threshold voltage, compare the measured voltage of the secondary battery with the second threshold voltage that is lower than the prescribed charging voltage while performing constant current charging with the set second charging current, decrease the second charging current to be third charging current when the measured voltage is higher than the second threshold voltage, and increase the second threshold voltage by a predetermined amount to be third threshold voltage, repeat a comparison of the measured voltage with the threshold voltage and a change of the charging current and a change of the threshold voltage, and complete rapid charging in a case where nth charging current is decreased to a predetermined value and the measured voltage is higher than the predetermined value.