A charging and discharging control circuit has over-charge detection circuits that monitor secondary batteries. A delay circuit generates a delay time in response to outputs from the over-charge detection circuits. A charging and discharging switch control circuit controls a charging and discharging switch circuit in response to outputs from the over-charge detection circuits and an output from the delay circuit. Detection circuits detect a voltage higher than an over-charge detection voltage of the secondary batteries. A circuit changes a state of the charging and discharging control circuit between a normal state for controlling charging and discharging of the secondary batteries and a test state for evaluating a characteristic of the charging and discharging control circuit in response to signals from the plurality of detection circuits.