Balanced charging of series connected battery cells

Novel method of charging and discharging the battery cells serially connected is presented. The principle is the control of charge stored in respective cells by using electronic switches so that the voltages of respective cells may be balanced automatically. The circuit to realize this principle is essentially the same as that of the ringing choke converter for the DC-to-DC power converter which is the simplest of minimum number of components. The cell voltage being low from 1.2 V to 3.6 V, the trench type MOSFET for the synchronous rectifier is used as a switching element.