Implementation and System-Level Modeling of a Hardware Efficient Cell Balancing Circuit for Electric Vehicle Range Extension

Abstract

This article presents a novel hardware-efficient battery balancing circuit for electric vehicle batteries that uses the low-voltage battery as a convenient source and sink for balancing. Compared to existing techniques, the proposed topology strikes a balance between the current industry standard of passive balancing and high component-count, high-cost solutions. For a battery pack consisting of n cells in series within m modules, the proposed design uses (n +1) bilateral switches for cell selection, and m low-voltage isolated dc/dc converters for cell balancing. Balancing can occur quickly during driving as the circuit can transfer energy between nonadjacent cells concurrently throughout the pack. This article presents the design, control, simulation results, and experimental results of the proposed architecture. Furthermore, system-level vehicle modeling shows an increase in driving range of 1.8%-20.1% for different balancing parameters on repeated Urban Dynamometer Driving Schedule and Highway Fuel Economy Driving Schedule cycles for an end-of-life pack, compared to passive balancing, which does not charge cells while driving.