Optimized Passive Cell Balancing for Fast Charging in Electric Vehicle

Abstract

Electric vehicles (EVs) are clean substitutes for conventional vehicles. Battery management system (BMS) is the intelligence behind the EV battery packs. One of the key functions of BMS is cell balancing, which balances the battery cells voltages equally during charging. Most of today’s EVs are adopting a passive cell balancing scheme, which uses fixed dissipative resistors to remove the extra charge from the overcharged cell to balance the charge in all the cells equally. One of the main concerns about the passive balancer is the balancing time. The long balancing time is manageable if the vehicle is charged through conventional charging (5–6 h) system and cell imbalance is minimum. Under fast DC charging scenarios as well as maximum imbalance condition, passive balancing with a fixed resistor is not an optimum solution. Either for fresh cell or aged cell, the passive cell balancing with variable balancing resistor is used based on the balancing current requirement under slow or fast charging scenarios are implemented. The passive system with variable resistor outcome is compared using Matlab-Simscape.

KEYWORDS:

• Battery management system
• Electric vehicle
• Fast charging
• Lithium-ion battery
• Passive cell balancing
• State of charge

Acknowledgements

This research work was supported by Robert Bosch Engineering and Business Solutions Limited, Bengaluru, India.

Additional information

Notes on contributors

D. Thiruvonasundari

D Thiruvonasundari is a PhD scholar at Amrita School of Engineering Bangalore, Amrita Vishwa Vidyapeetham, India, since August 2016. She obtained BE in electrical and electronics engineering from IRTT, Bharathiyar University, Tamil Nadu, India. She obtained MTech in power electronics from TOCE, Visvesvaraya Technological University (VTU), Bangalore, India. She served as an assistant professor from 2013. Her PhD work is to improve the operation of battery management system used in the electric vehicle applications.

K. Deepa

K Deepa graduated from Alagappa Chettiar College of Engineering and Technology, Tamil Nadu, India, in 1998. She obtained MTech degree from Anna University, Guindy campus, Tamil Nadu, India, in 2005. She received doctoral degree from Jawaharlal Nehru Technological University, Anantapur, A.P, in 2017. Currently, she is working as assistant professor in Department of Electrical and Electronics Engineering, Amrita School of Engineering, Amrita Vishwa Vidyapeetham University, Bangalore, Karnataka, India. She has 20 years of teaching experience. She is a life Member of IETE and ISTE, India and senior member of IEEE. She has authored two textbooks on “Electrical Machines” and “Control Systems”. She has published 27 papers international journals, 31 papers in international conferences and 6 papers in national conferences. Fifteen MTech degrees were awarded under her guidance. She is the advisor for the IEEE-PES and IAS student branch joint chapter and advisor for IEEE-WIE in Amrita School of Engineering, Bangalore, from 2015. She is also a joint treasurer for 2018 EXECOM of IEEE-PES Bangalore chapter. Her areas of interests include Power electronics, renewable energy technologies and control system engineering. Email: [email protected].