NOVELTY - A secondary battery system including at least two secondary batteries (201 to 20n) connected in series, comprises first diodes, each having an anode and a cathode; second diodes, each having an anode and a cathode; capacitors (101 to 10n) connected to junction portions; and an alternating current power source commonly connected to the junction portions through the capacitors, the alternating current power source selectively operating to produce an alternating current voltage.    USE - The secondary battery system is used for balancing voltage.    ADVANTAGE - The present invention provides inexpensive secondary battery system. In this secondary battery system, adjustment in voltage balance of the secondary batteries is achieved with a simple circuit without usage of a power transformer, so that satisfactory weight and cost of the secondary battery system is achieved.    DETAILED DESCRIPTION - A secondary battery system including at least two secondary batteries (201 to 20n) connected in series, comprises first diodes, each having an anode and a cathode, the anode being connected to a negative electrode of a corresponding secondary battery of the at least two secondary batteries connected in series; second diodes, each having an anode and a cathode, the cathode being connected to a positive electrode of the corresponding secondary battery, and the anode being connected to the cathode of a corresponding one of the first diodes; capacitors (101 to 10n) connected to junction portions, each of the junction portion being a connection between the cathode of a first diode of the first diodes and the anode of a second diode of the second diodes; and an alternating current power source commonly connected to the junction portions through the capacitors, the alternating current power source selectively operating to produce an alternating current voltage.    DESCRIPTION OF DRAWING(S) - The drawing shows a schematic view of a circuit showing a construction of a secondary battery system.    Capacitors (10-1 to 10-n)    Secondary batteries (20-1 to 20-n)    Resistor (30)    Charging circuit (100)    Diodes (101)    Power supply (102)    Voltages (V-1 to V-n)