The invention relates to a storage unit for storing electrical energy. The storage unit has at least one energy storage means. The energy storage means has at least one positive connection and at least one negative connection. The energy storage means is designed to be charged with electrical energy via the positive and the negative connection, and to output the electrical energy again via the connections. According to the invention, the storage unit has an electrically conductive contact rail which is connected to the positive connection, and has an electrically conductive contact rail which is connected to the negative connection. The contact rails each have at least one outer connection for the electrical connection of the storage unit.