A power supply unit, a distributed power supply system and an electric vehicle loaded therewith, capable of charge/discharge operation are disclosed. A first cell group is connected in parallel to a second cell group in which the electrolytic solution can be electrolyzed or the generated gas can be recombined. A plurality of the parallel circuit pairs are connected in series, and the series circuit is connected with a charger/discharger to constitute the power supply unit. The charger/discharger charges the power supply unit up to a voltage at which the electrolytic solution of the second cell group is electrolyzed or the generated gas is recombined.