In one aspect, there is disclosed a cell stack which can include cell modules connected in series to generate a stack operating voltage. The cell modules can include a battery cell in series with a series switch and include a shunt switch connected in parallel to the battery cell and the series switch. A stack monitor circuit can have a series control coupled to the series switch, a shunt control coupled to the shunt switch, and a battery cell monitor coupled to the battery cell for measuring a cell parameter from each cell module. Based on the measured cell parameter, the stack monitor circuit can select at least one cell module either to contribute to the stack operating voltage by closing the series switch and opening the shunt switch or to bypass the stack operating voltage by the opening the series switch and closing the shunt switch.