Battery pack and driving method thereof

The battery pack according to an embodiment of the present invention, a battery pack which can be connected with an external battery, connected to the internal battery, the measurement section for measuring a charging / discharging condition of the external battery, said internal battery and electrically, the charge / the discharge conditions are based, and includes an external battery and the power control section and a first connecting portion and second connecting portion electrically connected with the power control unit for controlling the output current level and input current level of the internal battery, the charging / discharging condition It is the first connection, comprising the SOC level of the external battery is connected to the power and control the external battery.