A device and method enable measuring individual cell voltages of cells in a cell stack of an energy accumulator. To this end, a series circuit formed of two diodes is connected in parallel to each cell, the nodes between these diodes are connected to a changeover switch via a respective capacitor and to a differential amplifier via the changeover switch, and an alternating current of a specified frequency and amplitude is fed into these capacitors while generating an alternating voltage corresponding to the cell voltage. This alternating voltage, after rectifying, becomes a direct voltage to ground value for the cell voltage.