Battery Charge Equalization-State of the Art and Future Trends


High-voltage battery packs which employ large series strings of battery cells can be found in many applications including utility industry, power backup, wheelchairs, electric, and hybrid vehicles. As the battery pack is charged and discharged as a single unit, differences in cell capacities, individual cell temperature, internal chemical characteristics, internal resistance, and degradation can cause capacity imbalances in the form of voltage variations. Imbalanced cell voltages can cause cell overcharging and over-discharging damage, and decrease the total storage capacity and lifetime of the battery pack. While balancing the voltages of the batteries will prevent any problems stemming from capacity mismatch, there are many ways to instantiate the solution. This paper reviews, analyses, and classifies various existing charge equalization techniques including capacitive, inductive, and transformer storage methods.

Meeting Name

Future Transportation Technology Conference (2005: Sep. 7-9, Chicago, IL)


Electrical and Computer Engineering

Keywords and Phrases

Battery Cells; Battery Pack; Cell Capacity; Cell Voltages; Charge Equalization; Chemical Characteristic; Future Trends; High-Voltages; Individual Cells; Internal Resistance; Power Backup; Storage Capacity; Utility Industry; Voltage Variation; Cells; Cytology; Degradation; Hybrid Vehicles; Charging (Batteries)

International Standard Serial Number (ISSN)


Report Number

Technical Paper 2005-01-3474

Document Type

Technical Report

Document Version


File Type





© 2005 Society of Automotive Engineers, All rights reserved.

Publication Date

01 Sep 2005