Embodiments of the present application provides an energy storage system, including: a first energy storage branch including a first battery cluster; a second energy storage branch including a second battery cluster and a first DC/DC converter, an output end of the first DC/DC converter being connected in series with the second battery cluster, and the first energy storage branch being connected in parallel with the second energy storage branch; where the first DC/DC converter is configured for adjusting an output current of the second energy storage branch, so that an output current of the first energy storage branch and the output current of the second energy storage branch are balanced. The energy storage system provided by the embodiments of the present application may maximize capacity of the energy storage system.