A protecting circuit monitors a voltage of a secondary battery and supplies the signal to permit a discharge to a gate terminal of a discharge control FET when the voltage is equal to or more than a lower limit value in a rated voltage range. When the discharge control FET receives this signal, it is connected and passes a discharge current. In the other cases, it shuts off the discharge current. Further, when the voltage is equal to or more than a predetermined value, a signal of a voltage of a battery voltage or more is supplied from a voltage converter to the gate terminal. When the voltage is equal to or less than an upper limit value in the rated voltage range, the protecting circuit supplies the signal to permit a charge to a gate terminal of a charge control FET. Further, when the voltage is equal to or more than a predetermined value, the voltage output from the voltage converter is supplied to the gate terminal. A battery pack in which by applying the voltage of the battery voltage or more to the gate terminal, the discharge control FET and the charge control FET are controlled and an energy loss is suppressed to the minimum is provided.