A battery pack includes a battery, main switch, controller, and driving voltage supply source. The battery has at least one battery cell. The main switch is connected between a first node and a second node, the battery is connected to the first node and an external terminal, and the external terminal connected to the second node. The controller manages the battery and to control the main switch. The driving voltage supply source generates a driving voltage based on a voltage of a third node and to supply the driving voltage to the controller. The third node is diode-connected to the first node and the second node.