Thermal Imaging of a Li-Ion Battery for the Estimation of the Thermal Parameters and Instantaneous Heat Dissipated

The electrochemical performance of a lithium-ion battery is strongly affected by the temperature. During charge and discharge cycles, batteries are subjected to an increment of temperature that can accelerate aging and loss of efficiency if critical values are reached. Knowing the thermal parameters that affect the heat exchange between the battery surface and the surrounding environment (air, cooling fins, plates, etc.) is fundamental to their thermal management. In this work, thermal imaging is applied to a laminated lithium-polymers battery as a noninvasive temperature-indication method. Measurements are taken during the discharge phase and the following cooling down until the battery reaches the ambient temperature. The 2d images are used to analyze the homogeneity of the temperature distribution on the battery surface. Then, experimental results are coupled with mathematical correlations. The derivation of the instantaneous heat generated in the battery and Newton's cooling law in transient conditions are used to estimate two main thermal parameters, as the convective heat transfer coefficient and the specific heat capacity, and then to calculate the heat generated by the battery. The experimentally-based derivation of the abovementioned thermal parameters will be useful in advanced thermal models for the design of batteries and battery cooling systems.