CELL BALANCER

PROBLEM TO BE SOLVED: To provide a cell balancer that can effectively use discharge energy obtained when performing a cell balance, while suppressing a dispersion of each output voltage of a plurality of secondary batteries constituting a main battery.SOLUTION: A cell balancer 1 comprises: a transformer 6 in which a primary coil 6-1 and a secondary coil 6-2 are electromagnetically coupled as an AC current flows into the primary coil 6-1 owing to an intermittent discharging of modules 13; a DC-DC converter 4 provided between the secondary coil 6-2 and an auxiliary battery 7; a battery ECU8 which, when output voltage differences of modules 13 are equal to or more than a threshold value, makes prescribed modules 13 discharge intermittently so that an output voltage of each module 13 becomes balanced, and also makes a voltage applied to the secondary coil 6-2 drop so as to charge the auxiliary battery 7 by an output voltage from the DC-DC converter 4.