Isothermal battery calorimetry analysis on a thermal behavior of Li-ion battery for electric vehicle

This paper presents the development of an isothermal battery calorimeter (IBC) for analyzing the thermal characteristics of high-capacity lithium-ion pouch cells used in electric vehicles. The IBC incorporated a Peltier module to maintain an isothermal environment within the test cell, and a PID control was employed for the operation. A Positive-Thermal-Coefficient (PTC) heater was used to calibrate the IBC and determine the heat generation rate of the battery during operation. The heat generation rate of a lithium-ion battery (LIB) was measured under various load conditions, including constant current discharge and driving profiles. The results were compared with those of conventional methods, such as equivalent electric circuit model (EECM)-based simulation and inverse heat analysis. This comparison demonstrated that the IBC accurately captured the thermal behavior of the pouch cell, which exhibited changes in the state of charge (SOC), similar to the inverse heat analysis. Additionally, the IBC effectively identified specific regions with significant heat generation, thus facilitating in the detection of serious heat problems within the battery under driving load conditions. Although a time delay in the heat generation rate was observed in the IBC, owing to the thermal inertia of the Peltier module, this issue could be mitigated by reducing the thermal mass of the module.