Power storage system, power storage device, and charging method

A power storage device comprising:

• a cell stack of a plurality of power storage cells connected in series;
• an alternating current excitating circuit that excitates a charging current to be supplied to the cell stack using an alternating current;
• a complex impedance measuring unit configured to measure a current value of the alternating current used to excitate the charging current and a voltage value of each of the plurality of power storage cells, and measure a complex impedance of each of the plurality of power storage cells from the measured current value and the measured voltage value;
• and
• a communication circuit that notifies a charging device that supplies the charging current of the complex impedance.

A charging method of charging a power storage device including a cell stack of a plurality of power storage cells connected in series, the charging method comprising:

• excitating a charging current to be supplied to the cell stack using an alternating current;
• measuring a current value of the alternating current used to excitate the charging current and a voltage value of each of the plurality of power storage cells;
• measuring a complex impedance of each of the plurality of power storage cells from the measured current value and the measured voltage value;
• and
• controlling the charging current based on the complex impedance.