An electrochemical generator comprises a stack of cells in series. To control the voltage across the terminals, controlling means comprise, for each cell, a first reactive passive component, the impedance varying depending on the DC voltage across its terminals, being biased by the voltage delivered by the cell, and a second reactive or resonant passive component forming, with the first reactive passive component, a series or parallel resonant circuit having a preset nominal resonant frequency for a nominal biasing voltage delivered by the cell. Using a variable frequency signal generator to supply the resonant circuits allows a detection circuit to detect resonant peak(s) across the terminals. The divergence between the resonant frequency corresponding to a detected peak and the nominal resonant frequency indicates the state of the associated cell. The frequency differences directly, for their part, provide information on the uniformity of the cells with respect to each other.
