STATE-OF-CHARGE BALANCING WITH PARALLEL AND SERIES OUTPUT CONNECTED BATTERY POWER MODULES

An apparatus includes a battery pack with N battery bricks, each with a DC output voltage. The output of each brick is connected in series providing a bus voltage. Each brick includes battery power modules (“BPMs”) connected in parallel and each connected to a battery cell. Each BPM charges/discharges the connected battery cell. Each brick has a battery brick controller that provides a control signal to each brick's BPMs. A control signal of a BPM is derived from a BPM error signal that includes a battery cell current of the battery cell of BPM subtracted from a summation of an average current signal, a local droop current and a balancing current. The balancing current is based on a current SOC of the battery cell connected to the BPM and a desired SOC for the battery cell connected to the BPM. A BMS derives the balancing current for the BPMs.