Entropy Coefficient and Thermal Time Constant Estimation From Dynamic Thermal Cycling of a Cylindrical LiFePO₄ Battery Cell

This paper presents a method for estimating (i) the reciprocal of the thermal time constant of a lithium-ion battery cell and (ii) the cell’s entropy coefficients for different states of charge. The method utilizes dynamic battery temperature cycling for parameter estimation. The paper demonstrates this method specifically for a cylindrical lithium iron phosphate (LiFePO₄) cell. Identifying battery thermal parameters is important for accurate thermo-electrochemical modeling and model-based battery management. Entropy coefficients have been identified in previous research for various battery chemistries using calorimetric and potentiometric measurements requiring quasi-equilibrium conditions. This work, in contrast, fits the entropy coefficients and the reciprocal of the thermal time constant of a first-order thermal model to datasets collected in a noninvasive, dynamic experiment. This reduces the time required for parameter identification by a factor of 3 compared to traditional quasi-equilibrium experiments.