A battery pack and method are disclosed that permanently disable the battery pack on portable electronic equipment if the battery pack has been inauthentically remanufactured. An output voltage value and a discharge current value of the battery block are measured regularly and an amount of change in the output voltage value per unit time is calculated. If the amount of change in the output voltage value per unit time or the discharge current value exceeds predetermined values, operation of an electric circuit involved in charge/discharge operations of the battery pack is permanently disabled.