Electrical energy storage system comprising a plurality of electrochemical energy stores, which are electrically connectable to primary connection poles of the electrical energy storage system for providing a primary voltage; secondary connection poles for providing a secondary voltage, wherein the secondary connection poles are electrically connectable to an electric power source by means of secondary switches; at least one first primary switch, which is electrically connected to an electrical connection between two of the electrochemical energy stores and to an electrical connection between a first secondary switch and a first secondary connection pole, wherein the electrochemical energy stores electrically connected between the electrical connection and a second primary connection pole are electrically connectable to the first secondary connection pole of the electrical energy storage system by means of the first primary switch to provide a secondary voltage, which is lower than the primary voltage.