Dynamic thermal performance and management analysis for a 48 V lithium-ion battery pack under real-world driving conditions

This study investigates the thermal behavior of a 48 V lithium-ion battery (LIB) pack under dynamic operating conditions using experimental and numerical methods. While most existing research targets high-voltage systems or steady-state scenarios, this work addresses the overlooked case of low-voltage packs under realworld transient loads. An indirect liquid cooling mechanism was utilized, activating at approximately 40 ◦C. Five test cases were examined: a full charge-discharge cycle (Case 1), worldwide harmonized light duty test cycle (WLTC) profiles and their inverted versions at initial state of charge (SOC) levels of approximately 90% and 60% (Cases 2 and 3), and the effects of initial temperature and temperature difference, the difference between the highest and lowest temperature points within the pack (Cases 4 and 5). Thermal behavior was analyzed at cell, module, and pack levels using 27 thermocouples, whose utilization is rarely documented in literature. A sensitivity analysis identified the specific heat and density of the cells as key parameters influencing thermal predictions, highlighting the importance of precise thermophysical characterization. Results indicated temperature variation across modules, influenced by cooling strategy. Maximum temperature rises during WLTC driving cycles were 10.5 ◦C, 11.4 ◦C, and 9.1 ◦C for Cases 2, 3, and 4, respectively, highlighting the influence of initial SOC and temperature. Although the initial temperature difference did not affect temperature rise, it influenced temperature gradients (Case 5). The indirect liquid cooling system effectively maintained pack temperatures below 40 ◦C under WLTC and inverted conditions, while constant high-current cycling led to higher peaks around 46 ◦C. These findings underscore the complexity of thermal management in LIB packs under dynamic conditions and emphasize the effectiveness of indirect liquid cooling in limiting temperature rise. This work offers practical insights for optimizing alternative battery thermal management strategies in electric vehicle applications.