Current sensorless diagnosis of the cell internal resistance consistency in a parallel module using relaxation voltage

Shumao Wang, Wenkang Bao, Yuedong Sun, Xiangjun Li, Feng Dai, Jianfeng Hua and Yuejiu Zheng

Energy, 2024, vol. 301, issue C

Abstract: The non-uniform performance of parallel cells in practical applications can lead to safety concerns, such as current overload, accelerated aging, and lithium plating. While overall voltage and current of parallel modules can be obtained, assessing the consistency among branch cells remains challenging due to the lack of direct branch current measurements. This paper introduces a method for accurately discerning the internal resistance consistency of parallel cells based on the relaxation voltage exhibited by the module. Analyzing the discharge process of parallel cells with different internal resistances, the link between internal resistance consistency and relaxation voltage recovery is discussed, and the effect of branch currents crossover is noted. A series of parallel modules are designed for experiments, and the results show that different internal resistance consistencies monotonically affect the recovery of the terminal voltage in the relaxation phase when discharge is stopped before the parallel branch currents crossover. Thus, the internal resistance consistency can be judged by the behavior of the relaxation voltage. A faster terminal voltage recovery of the module in the relaxation phase indicates better internal resistance consistency. This method requires only terminal voltage data and no additional sensors, which provides superior economy and practicality for real applications.

Keywords: Parallel cell module; Internal resistance consistency; Relaxation voltage; Branch current; Sensorless diagnosis (search for similar items in EconPapers)
Date: 2024
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Persistent link: https://EconPapers.repec.org/RePEc:eee:energy:v:301:y:2024:i:c:s036054422401541x

DOI: 10.1016/j.energy.2024.131768

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