Improved Performance of Serially Connected Li-Ion Batteries With Active Cell Balancing in Electric Vehicles

• Published in: IEEE transactions on vehicular technology Vol. 60; no. 6; pp. 2448 - 2457
• Main Authors: Einhorn, M., Roessler, W., Fleig, J.
• Format: Journal Article
• Language: English
• Published: New York, NY IEEE 01.07.2011; Institute of Electrical and Electronics Engineers; The Institute of Electrical and Electronics Engineers, Inc. (IEEE)
• Subjects: Applied sciences; Batteries; battery management systems; Charge; Circuit properties; Convertors; Current measurement; dc-dc power converters; Direct current; Direct energy conversion and energy accumulation; Discharge; Discharges; Electric potential; Electric vehicles; Electric, optical and optoelectronic circuits; Electrical engineering. Electrical power engineering; Electrical machines; Electrical power engineering; Electrochemical conversion: primary and secondary batteries, fuel cells; Electronic circuits; Electronics; energy storage; Exact sciences and technology; Ground, air and sea transportation, marine construction; Mathematical models; Prototypes; Road transportation and traffic; Signal convertors; Simulation; Studies; Voltage; Voltage measurement; Windings; Performance evaluation; Prototype; electric vehicles; Stacking; dc-dc power converters; Alkaline storage battery; Direct current convertor; Flyback converter; Voltage regulation; Power system stability; Secondary cell; Electric vehicle; Batteries; battery management systems; DC-DC power convertors; Lithium battery; System simulation; Gain; Energy storage
• ISSN: 0018-9545; 1939-9359
• DOI: 10.1109/TVT.2011.2153886

This paper presents an active cell balancing method for lithium-ion battery stacks using a flyback dc/dc converter topology. The method is described in detail, and a simulation is performed to estimate the energy gain for ten serially connected cells during one discharging cycle. The simulation is validated with measurements on a balancing prototype with ten cells. It is then shown how the active balancing method with respect to the cell voltages can be improved using the capacity and the state of charge rather than the voltage as the balancing criterion. For both charging and discharging, an improvement in performance is gained when having the state of charge and the capacity of the cells as information. A battery stack with three single cells is modeled, and a realistic driving cycle is applied to compare the difference between both methods in terms of usable energy. Simulations are also validated with measurements.