Patent ID: 8232768

Claim:
A cell balancing system, comprising: a plurality of battery modules, said battery modules each comprising: a plurality of battery cells; a battery management module coupled to said battery cells and configured to acquire cell voltages of said battery cells in each of said battery modules, and to compare said cell voltages to obtain a minimum cell voltage among said cell voltages in each of said battery modules; and a plurality of balance circuits coupled to said battery cells and configured to perform a balance operation on said battery cells under control of said battery management module; and a controller coupled to said battery modules and configured to receive a plurality of voltage signals from said battery modules, respectively, wherein each of said voltage signals indicates a minimum cell voltage associated with a corresponding battery module, wherein said controller compares said voltage signals to generate a reference signal indicating an overall minimum voltage among cell voltages of said battery cells in all said battery modules, wherein said cell balancing system compares each of said cell voltages to said reference signal, and wherein said battery management module in each of said battery modules controls said balance circuits according to a result of said comparison to balance said battery cells, thereby achieving cell balance among said battery modules.