POWER STORAGE SYSTEM, POWER STORAGE DEVICE, AND CHARGING METHOD

A power storage system (1) includes: a power storage device (100) including a cell stack (101) including power storage cells (B0 to B5) connected in series; and a charging device (200) that supplies a charging current to the power storage device (100). The power storage system (1) further includes: an alternating current excitating circuit (148) in the power storage device (100) or the charging device (200) that excitates the charging current using an alternating current; a complex impedance measuring unit (110) in the power storage device (100) that measures a current value of the alternating current used to excitate the charging current and a voltage value of each of the power storage cells (B0 to B5), and measures a complex impedance of each of the power storage cells (B0 to B5) from the measured current and voltage values; and a charging control unit in the power storage device (100) or the charging device (200) that controls the charging current based on the complex impedance.