Inverse Heat Transfer Analysis Method to Determine the Entropic Coefficient of Reversible Heat in Lithium-Ion Battery

Abstract

An entropic coefficient of reversible entropic heat is a key parameter in determining the battery thermal responses, but its measurement is challenging due to time consuming and inaccurate traditional methods. In this regard, an analytical approach based on the inverse heat transfer problem is newly proposed to precisely determine the entropic coefficient with low experiment cost. Experiments are conducted by discharging the battery under four different current rates to inversely estimate the entropic coefficients, and the least squares regression are conducted to optimize the derived entropic coefficients. Through the comparison with the existing potentiometric method, the experimental time can be reduced by 93.7%. Furthermore, the accuracy of the proposed method is well verified by validating within the root mean square error of 0.848°C by comparing with the experimental results. Through the validation processes under various operating conditions, such as low to high current rates, charging process, dynamic loads, and different ambient temperatures, the proposed method is proven over temperatures ranging from 10°C to 60°C. Conclusively, the proposed method can be a great alternative to replace the classical experimental methods.

Comparative Evaluation of Liquid Cooling-Based Battery Thermal Management Systems: Fin Cooling, PCM Cooling, and Intercell Cooling

“…However, current study utilized the lumped thermal capacity model, which assumed the battery as a uniform heat generation model, considering the Biot number (Bi). Generally, if the Biot number is less than 0.1, we can assume the lumped thermal capacity model International Journal of Energy Research [35]. Therefore, the Biot number for all direction was calculated as…”

“…Bi x , Bi y , and Bi z are the Biot number for x-, y-, and z-direction, respectively, and h and L c are the convective heat transfer coefficient and characteristic length for each direction. The convective heat transfer coefficient is 2.3 W•m -2 •K -1 which is calculated using a generalized reduced gradient algorithm developed in our previous study [35]. k x , k x , and k x are the x-, y-, and z-directional thermal conductivity of battery, respectively.…”

“…Unlike other values, the entropy coefficient cannot be directly obtained from experiments and requires a special calculation method. In this study, it was determined using an inverse heat transfer analysis method, which was developed in our previous study [35].…”