In one aspect, the invention comprises an apparatus for balancing cells in a series string of modules having cells. The apparatus comprises a processing system and a communication circuit. The processing circuit is configured to receive an average cell voltage value from each module. The processing circuit is further configured to determine an overall average cell voltage for all the cells. The processing circuit is also configured to cause each the modules to determine a relative capacitance for each of its cells and cause each of the modules to balance its cells based on the respective relative capacitances. The communication circuit is configured to receive the average cell voltage value from the modules.