Analytical thermal model for characterizing a Li-ion battery cell

In a scenario of small and customized production of electric vehicle, it is important to set methods and tools to evaluate the Li-Ion cells heat source in EV battery. The main problem of the new lithium batteries is represented by the need to keep the battery packs at uniform and constant temperatures and avoid peaks of temperatures which cause degradation of performance and safety problem. The main issue concerns the characterization of a thermal model to calculate the heat generated by electrochemical reactions in a single battery cell. In order to achieve this objective, electrical tests have been conducted to obtain the parameters such as voltage curves, open circuit voltage, and capacity for different type of Li-Ion cells and different rate of current in charge and discharge. During experiments, the use of an IR camera allows to acquire real temperature data under working conditions. These tests concern one cell per time, analyzed in natural convection condition at constant external temperature. The heat generation is evaluated solving the analytical thermal formula which depends on the current rate. The approach has been validated comparing the calculated temperature values with experimental data. The proposed methodology allows to determine the heat generated and temperature for different working condition.