A Modularized Charge Equalizer for an HEV Lithium-Ion Battery String

• Published in: IEEE transactions on industrial electronics (1982) Vol. 56; no. 5; pp. 1464 - 1476
• Main Authors: Park, H.-S., Kim, C.-E., Kim, C.-H., Moon, G.-W., Lee, J.-H.
• Format: Journal Article
• Language: English
• Published: New York IEEE 01-05-2009; The Institute of Electrical and Electronics Engineers, Inc. (IEEE)
• Subjects: Batteries; Charge; Control systems; Design engineering; Electric vehicles; Equalizers; Grounding; Hybrid electric vehicle (HEV); Hybrid electric vehicles; Hybrid vehicles; Lithium-ion batteries; lithium-ion battery; Logic design; Low voltage; modularized charge equalization; module balancing transformer (MBT); Power rating; Stress; Strings; System-level design; Voltage control
• ISSN: 0278-0046; 1557-9948
• DOI: 10.1109/TIE.2009.2012456

Based on the fact that a hybrid electric vehicle (HEV) connects a high number of batteries in series to obtain more than approximately 300 V, this paper proposes a modularized charge equalizer for an HEV battery pack. In this paper, the overall battery string is modularized into M*N cells, where M is the number of modules in the string and N is the number of cells in each module. With this modularization, low voltage stress on the electronic devices can be achieved, which means that there is less chance of a failure on the charge equalizer. The power rating selection is one of the most important design issues for a charge equalizer because it is very closely related to equalization time. To solve this problem optimally, this paper presents a power rating design guide. In addition, this paper considers system-level design issues, such as cell voltage acquisition, equalizer control logic, and system-level grounding. The simulation and experimental results are presented to show the usefulness of the optimal power rating selection guide and the low voltage stressed charge equalization process.