A sensor circuit is provided for monitoring four cells of a battery. The sensor circuit provides a maximum terminal cell voltage and a minimum terminal cell voltage. In a switched capacitor embodiment, one comparator compares the cells, two at a time. The output of the comparator is provided to a maximum state machine and a minimum state machine which select the cells with the highest and lowest voltages, respectively. In a continuous system embodiment, six comparators continuously monitor the cell voltages. The comparator outputs are provided to a maximum logic circuit and a minimum logic circuit which select the cells with the highest and lowest voltages, respectively, and provides a maximum and a minimum terminal voltages signals. These maximum and minimum terminal voltage signals are provided so that a charge controller can monitor the cells for overcharge and discharge conditions.