Equalization integrated online monitoring of health map and worthiness of replacement for battery pack of electric vehicles

• Published in: Journal of power sources 2013-02, Vol.223, p.293-305
• Main Authors: Ugle, Rohit, Li, Yaoyu, Dhingra, Anoop
• Format: Article
• Language: English
• Subjects: Applied sciences; Battery equalization; Direct energy conversion and energy accumulation; Electric vehicle; Electrical engineering. Electrical power engineering; Electrical power engineering; Electrochemical conversion: primary and secondary batteries, fuel cells; Exact sciences and technology; Ground, air and sea transportation, marine construction; Internal resistance; Road transportation and traffic; Subspace identification; Worthiness of replacement
• ISSN: 0378-7753; 1873-2755
• DOI: 10.1016/j.jpowsour.2012.09.083

Ever increasing acceptance of electric vehicles relies on better operation and control of large battery packs. The individual modules in large battery packs cannot have identical characteristics and may degrade differently due to manufacturing variability and other factors. Degraded battery modules waste more power, affecting the performance and economy for the whole battery pack. Also, such impact varies with different trip patterns. It is beneficial if the performance gain can be evaluated online prior to replacing certain battery module regarding to actual driving. In this paper, the research objectives are two-fold. First, we propose an on-line battery module degradation diagnostic scheme using the intrinsic signals of battery module equalization. Without need for additional sensors or offline tests, this scheme is cost-effective for constructing and updating the battery pack “health map” in real time during the vehicle operation. Secondly, based on the derived battery health map, the Worthiness of Replacement (WOR) for certain modules/cells is proposed to evaluate the performance of the battery pack for customer specified trip. Such evaluation index provides a quantitative measure for module replacement and battery pack swapping Simulation study is performed to validate the proposed ideas using an actual driving cycle recorded for a commuting trip.