the invention relates to an energy storage assembly , comprising a plurality of cells connected in series , wherein the series connection of cells is connected to a power output of the energy storage assembly and a control unit , wherein at least a part of the cells connected in series is connected to the power output and the control unit by way of potential - free controlled converter and control units connected in parallel , such that during the charging , discharging and recharging processes each of the cells is operated according to the individual performance characteristics of said cell by means of selective current drains by the converter and control units and a total current flowing at the power output of the energy storage assembly is formed by a base current flowing through the series connection of the cells and by additional currents , which are drained from the individual cells depending on the capacity of the cells . the invention allows for the interconnection of different cell types to form an energy storage assembly and for uniform charging or discharging thereof , thus facilitating optimal use of the energy stored and extending the total usage period .