Balancing apparatus, balancing method and battery module

A balancing apparatus is an apparatus for balancing the cells connected in series including: bi-directional switches, that are connected with each cells, to control a flow of electric current bi-directionally; a controller for measuring the voltages of the cells and controlling to turn on/off the bi-directional switches that are connected to the selected cells based on the measured voltages; and a multi winding transformer connected to the bi-directional switches and transferring energy between the cells when the bi-directional switches are turned on. [Reference numerals] (11) Bi-directional switches; (110) Module; (12) Multi winding transformer; (13) Control unit; (AA,BB,CC) Cell