An energy storage apparatus, wherein the energy storage apparatus is configured to supply power to a power grid; the energy storage apparatus comprises: a plurality of battery clusters, a plurality of conversion units, a start unit, and a controller; the power grid is configured to supply power to the controller, the controller comprises a plurality of control units, the plurality of battery clusters are in a one-to-one correspondence with the plurality of control units and the plurality of conversion units, and each battery cluster is connected to a corresponding conversion unit; each battery cluster comprises a battery pack and a control switch; and each conversion unit comprises a direct current to direct current DC-DC converter, and each DC-DC converter is connected to a direct current bus; the start unit is configured to: after receiving a start signal, control the control switch in at least one of the plurality of battery clusters to closed position, to start a control unit corresponding to the at least one battery cluster; and any one of the plurality of control units is configured to: detect, based on a state of the control switch in the corresponding battery cluster, whether a black start mode is on; and when the black start mode is on, control the DC-DC converter in the corresponding conversion unit to release electric energy stored in the battery pack in the corresponding battery cluster, to energize the direct current bus, wherein the black start mode is a mode in which power supply to the power grid needs to be restored after the power grid is powered off, wherein each control unit comprises a battery management unit, BMU; any battery management unit in the plurality of control units is configured to: detect the state of the control switch in the battery cluster corresponding to the control unit; determine whether the black start mode is on; and when the control switch in the battery cluster corresponding to the control unit is closed, determine that the black start mode is on; characterized in that each battery cluster further comprises: a first auxiliary power supply; in each battery cluster, a first electrode of the control switch is connected to one end of the first auxiliary power supply, a second end of the battery pack is connected to the other end of the first auxiliary power supply, the first electrode of the control switch is further connected to the start unit, a second electrode of the control switch is separately connected to a first end of the battery pack and the start unit, and a control electrode of the control switch is connected to the first auxiliary power supply; and the first auxiliary power supply in any one of the plurality of battery clusters is configured to: after the control switch in the battery cluster is closed, supply power to a battery management unit in the control unit corresponding to the battery cluster. the start unit is configured to: after receiving a start signal, control the control switch in at least one of the plurality of battery clusters to closed position, to start a control unit corresponding to the at least one battery cluster; and any one of the plurality of control units is configured to: detect, based on a state of the control switch in the corresponding battery cluster, whether a black start mode is on; and when the black start mode is on, control the DC-DC converter in the corresponding conversion unit to release electric energy stored in the battery pack in the corresponding battery cluster, to energize the direct current bus, wherein the black start mode is a mode in which power supply to the power grid needs to be restored after the power grid is powered off, wherein each control unit comprises a battery management unit, BMU; any battery management unit in the plurality of control units is configured to: detect the state of the control switch in the battery cluster corresponding to the control unit; determine whether the black start mode is on; and when the control switch in the battery cluster corresponding to the control unit is closed, determine that the black start mode is on; characterized in that each battery cluster further comprises: a first auxiliary power supply; in each battery cluster, a first electrode of the control switch is connected to one end of the first auxiliary power supply, a second end of the battery pack is connected to the other end of the first auxiliary power supply, the first electrode of the control switch is further connected to the start unit, a second electrode of the control switch is separately connected to a first end of the battery pack and the start unit, and a control electrode of the control switch is connected to the first auxiliary power supply; and the first auxiliary power supply in any one of the plurality of battery clusters is configured to: after the control switch in the battery cluster is closed, supply power to a battery management unit in the control unit corresponding to the battery cluster.