A controller of a power storage system includes a voltage measuring device configured to be electrically coupled to at least one cell and to generate first voltage data, the first voltage data comprising a first voltage value and a first voltage measurement time of a voltage of the at least one cell, and a current measuring device configured to be electrically coupled to the at least one cell and to generate first current data, the first current data comprising a first current value and a first current measurement time of a current through the at least one cell, the first voltage measurement time corresponding to the first current measurement time in a first measuring period, a battery management system configured to generate a clock signal transmitted to the voltage measuring device and the current measuring device to synchronize the first voltage data and the first current data in a first transmission period of the first measuring period.