Combined PI feedback and feedforward cell balancing method

A method and system for battery pack cell state of charge balancing using a proportional-integral feedback control combined with a feedforward control. The proportional-integral feedback control acts on the difference between the average discharge for all cells over a previous driving cycle and the discharge of a specific cell over the previous driving cycle. Thus, the feedback term is based on whether an individual cell discharges more quickly or less quickly than the battery pack average during driving. A cell which discharges more quickly will receive decreased resistive discharge balancing. The feedforward control acts on the difference between an individual cell's state of charge and the battery pack average state of charge at the beginning of a current driving cycle. The overall control effort, which determines the resistive discharge balancing on-time duty cycle for each cell, is the sum of the feedback control signal and the feedforward control signal.