An energy storage system and method of driving the same are disclosed. In one aspect, the energy storage system comprises a battery system, a direct current (DC) contactor, first and second power supply units, and a first switch. The battery system includes at least one battery rack and at least one rack battery management system (BMS). The DC contactor is located between the battery system and a power conversion system. The first power supply unit is configured to be electrically connected to the DC contactor. The second power supply unit electrically connected to the rack BMS. The first switch is electrically connected to the rack BMS, wherein the rack BMS is configured to electrically disconnect the DC contactor from the first power supply unit when the first switch is turned on.