This paper introduces a pseudo three-dimensional electrochemical-thermal coupled battery model for a cylindrical Lithium Iron Phosphate battery. The model comprises a pseudo two-dimensional electrochemical cell model coupled with three-dimensional lumped thermal model. The cell is disassembled to obtain the physical dimensions of the cell components. The thermal characteristics of the cell are studied during the discharge process over a range of temperatures and discharge rates. The validity of the numerical model is demonstrated experimentally via a 26650 cylindrical Lithium Iron Phosphate/graphite battery cylindrical cell.Instead of infrared thermal images, series of regression models are utilized to quantify the thermal behavior at various depth of discharge under various discharge rates. The results demonstrated that the battery cell performs differently at a lower ambient temperature and lower discharge rate where the exothermic reactions are milder.

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This paper presents an integrated state-of-charge (SOC) estimation model and active cell balancing of a 12-cell lithium iron phosphate (LiFePO4) battery power system. The strong tracking cubature extended Kalman filter (STCEKF) gave an accurate SOC prediction compared to other Kalman-based filter algorithms. The proposed groupwise balancing of the multiple SOC exhibited a higher balancing speed and lower balancing loss than other cell balancing designs. The experimental results demonstrated the robustness and performance of the battery when subjected to current load profile of an electric vehicle under varying ambient temperature.

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