• CN: 11-2187/TH
  • ISSN: 0577-6686

Journal of Mechanical Engineering ›› 2019, Vol. 55 ›› Issue (20): 60-72,84.doi: 10.3901/JME.2019.20.060

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Online Diagnostic Method for Health Status of Lithium-ion Battery in Electric Vehicle

JIANG Jiuchun1,2, GAO Yang1, ZHANG Caiping1, WANG Yubin1, ZHANG Weige1, LIU Sijia1   

  1. 1. School of Electrical Engineering, Beijing Jiaotong University, Beijing 100044;
    2. Shenzhen Presisi Testing Technology Co., Ltd., Shenzhen 518108
  • Received:2019-05-19 Revised:2019-08-10 Online:2019-10-20 Published:2020-01-07

Abstract: With the rapid development of electric vehicles, the attenuation of high-energy lithium-ion batteries has received increasing attention. Battery health status is a core parameter of durability management, which is essential for extending battery life and improving system reliability. Taking the ternary material lithium ion battery as the research object, based on the open circuit voltage model of positive and negative electrodes, the matching relationship between positive and negative electrodes and the whole battery is described, and the open circuit voltage-state of charge curve is reconstructed on the new battery scale. The evolution characteristics of the positive and negative matching relationship after the battery experiences various aging modes are analyzed, thereby reconstructing the open circuit voltage-state of charge curve of the aging battery on the new battery scale. Based on this, an improved non-destructive quantitative diagnosis method for lithium ion battery aging mode is proposed, which overcomes the limitation that the existing method must take the real open circuit voltage-state of charge curve of the battery as the diagnostic basis, so it is more suitable for real vehicle online application. The extended Kalman filter algorithm is used to identify the curve of the open circuit voltage with the discharge capacity from the battery dynamic current discharge data, and the proposed aging diagnosis method is used to fit the open circuit voltage curve, which can quantitatively analyze the material loss of positive electrode, negative electrode and available lithium ions. On this basis, the estimation method of the maximum available capacity of the battery and the identification method of the true open circuit voltage-state of charge curve are presented. The results show that the capacity estimation error of the method under dynamic conditions is less than 1%, and the root mean square error of the open circuit voltage-state of charge curve is within 6 mV. The method is applied to a battery pack, and can realize the estimation of maximum available capacity and the state of charge consistency of each single battery in the battery pack.

Key words: lithium-ion battery, aging mode, quantitative analysis, health status, online diagnosis

CLC Number: