Identification and analysis of model parameters used for LiFePO4 cells series battery pack at various ambient temperature

Owing to cell-to-cell variations in battery pack, it is hard to manage cells of the battery pack safely and effectively. As a result, the battery pack performance is rapidly degraded, which in turn spread the differences in individual cells. Ambient temperature is a significant factor that influences the characteristics of lithium-ion battery and cell variations in the pack. This study tries to put effort in researching the temperature characteristics of cells series battery pack. The battery model parameters identification tests are designed to analyse the inconsistency characteristics of cells [such as open-circuit voltage (OCV), ohmic and polarisation resistances and polarisation capacitance] under various ambient temperatures. The results indicate that ohmic and polarisation resistances are most significantly increased as the temperature decreases, whereas OCV is opposite. The variation of cells inconsistency characteristics is obvious along with the temperature change. Comprehensive above factors, the change rate of battery pack capacity is faster than that of a single cell with the drop in temperature.