A method of operating a battery system comprising a plurality of battery cells coupled in series and a plurality of converter stages , wherein each stage of the plurality of converter stages comprises an inductor , a switch (S14, S24, S34, S44), and a capacitor , and wherein the plurality of battery cells includes at least three battery cells coupled in series and each cell of the plurality of battery cells is associated with a converter stage of the plurality of converter stages, the number of battery cells being equal to the number of converter stages, the method comprising: determining a cell with a greatest charge excess of the plurality of battery cells; determining a cell with a greatest charge deficit of the plurality of battery cells; discharging the cell with the greatest charge excess in order to charge, with a voltage converter, the cell with the greatest charge deficit , wherein the discharging comprises: using a converter stage associated with the cell with the greatest charge excess as a source stage of the voltage converter, and using a converter stage associated with the cell with the greatest charge deficit as a sink stage of the voltage converter; wherein using a converter stage associated with the cell with the greatest charge excess as a source stage of the voltage converter, and using a converter stage associated with the cell with the greatest charge deficit as a sink stage of the voltage converter, comprises configuring the voltage converter as a single-ended primary inductor converter, SEPIC. the method comprising: determining a cell with a greatest charge excess of the plurality of battery cells; determining a cell with a greatest charge deficit of the plurality of battery cells; discharging the cell with the greatest charge excess in order to charge, with a voltage converter, the cell with the greatest charge deficit , wherein the discharging comprises: using a converter stage associated with the cell with the greatest charge excess as a source stage of the voltage converter, and using a converter stage associated with the cell with the greatest charge deficit as a sink stage of the voltage converter; determining a cell with a greatest charge excess of the plurality of battery cells; determining a cell with a greatest charge deficit of the plurality of battery cells; discharging the cell with the greatest charge excess in order to charge, with a voltage converter, the cell with the greatest charge deficit , wherein the discharging comprises: using a converter stage associated with the cell with the greatest charge excess as a source stage of the voltage converter, and using a converter stage associated with the cell with the greatest charge deficit as a sink stage of the voltage converter; using a converter stage associated with the cell with the greatest charge excess as a source stage of the voltage converter, and using a converter stage associated with the cell with the greatest charge deficit as a sink stage of the voltage converter; wherein using a converter stage associated with the cell with the greatest charge excess as a source stage of the voltage converter, and using a converter stage associated with the cell with the greatest charge deficit as a sink stage of the voltage converter, comprises configuring the voltage converter as a single-ended primary inductor converter, SEPIC. <EOS>