The invention relates to an energy storage system for a repeated drawing/intake, storage and release of electrical energy having a control unit and an energy store comprising a plurality of storage cells that are organized in storage modules, with the control unit being configured to separately determine the state of charge of at least some of the storage cells. The control unit is configured to recognize whether at least one storage cell should be removed; to electrically disconnect the storage cell to be removed from the remaining storage cells after the recognition that at least one storage cell should be removed; to recognize whether the disconnected storage cell has been replaced by a new storage cell; and to electrically connect the new storage cell to the remaining storage cells.