The invention relates to an energy storage device, particularly for an automobile, that comprises: an assembly (2) of serially-connected energy storage cells; a balancing circuit adapted for balancing the cells during the discharge thereof by enabling the flow of one or more balancing currents in one or more cells of the assembly (2); optionally a diagnosis system (61) for providing at least one piece of information associated with at least one cell in the assembly; wherein the balancing circuit (10; 41) is adapted for controlling the balancing current(s) based at least on external information independent from the energy-storage cell assembly and/or information associated with at least one of the cells and provided by the optional diagnosis system.