A battery pack including first and second battery contactors respectively having first ends electrically connected to positive and negative electrode terminals of a battery; first and second charging contactors respectively having first ends electrically connected to second ends of the first and second battery contactors; a second power connector of a charger having first and second output terminals respectively electrically connected to the first and second input terminals being connected to the first power connector; and a control unit configured to, when a charging voltage is applied from a power source of the charger to the battery pack between the first output terminal and the second output terminal, control at least one of the first charging contactor and the second charging contactor to change between a turn-on state and a turn-off state to diagnose a fault of each of the first charging contactor and the second charging contactor.