Mathematical fitting for the variation in capacity of lithium iron phosphate batteries corresponding to cycles

Chi-Yao Chung, Kung-Yen Lee, Zih-Yeh Lin, Shuen-De Wu, Chiao Fu, Kuan-Ming Li, Kang Li, Huei-Jeng Lin


It is well known that the capacity of lithium iron phosphate (LiFePO\(_{4}\)) batteries decreases as the usage cycles increase. In order to investigate the relationship between the number of charge/discharge cycles and the battery capacity, two batteries were cyclically charged and discharged using an automatic testing system, while simultaneously collecting the capacity data. The tested batteries were composed of different materials and had a capacity of 15 Ah. Each battery was cyclically charged and discharged 800 times. The batteries are analyzed and compared with each other to create fitted curves. The developed mathematical fitting, which consists of both exponential and polynomial terms, is closely responsive to the battery capacity.

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