State of charge equalizing device and assembled battery system including same

A state of charge equalizing device equalizing the state of charge of each cell of a plurality of cells connected to each other in series to form an assembled battery, comprising:

• a plurality of charging/discharging circuits connected in parallel to the respective cells to discharge and/or charge the respective cells;
• a plurality of voltage measurement circuits connected to the respective charging/discharging circuits to measure the voltages across the respective cells;
• and a control circuit controlling an operation of each of the charging/discharging circuits based on the measurement result of each of the voltage measurement circuits,
• the control circuit comprising:
• an equalization target voltage calculating unit calculating an equalization target voltage based on the voltages measured by the plurality of voltage measurement circuits before the plurality of charging/discharging circuits start discharging or charging;
• a charging/discharging starting unit that starts discharging or charging the cells each having a voltage thereacross different from the equalization target voltage calculated by the equalization target voltage calculating unit, by means of the respective charging/discharging circuits;
• a correcting unit correcting the equalization target voltage to thereby calculate a corrected equalization target voltage for each of said cells based on the difference between the voltage measured by the voltage measurement circuit before the charging/discharging circuit starts discharging or charging the cell and the voltage measured by the voltage measurement circuit after a certain period of time elapses from when the charging/discharging circuit starts discharging or charging the cell;
• and
• a discharging or charging ending unit that ends the discharge or charge of each of said cells by the charging/discharging circuit when the voltage measured by the voltage measurement circuit reaches the corrected equalization target voltage calculated by the correcting unit.