Design and Analysis of a Battery Thermal Management System for Fast Charging in Extreme Hot Condition

<div class="section abstract"><div class="htmlview paragraph">Fast charging of lithium-ion batteries presents significant thermal management challenges, due to the high demanding conditions of high C-rates, particularly at extreme ambient temperatures. This study explores the thermal behavior of a cylindrical lithium-ion cell during fast-charging scenarios designed to achieve a full charge in 15 minutes or less (SOC: 0%–100%), across a wide range of ambient temperatures. The analysis covers a broad spectrum of ambient temperatures, from 303 K to 333 K, addressing real-world operational challenges faced by electric vehicles and energy storage systems. A validated thermal model, calibrated with experimental data on the open circuit voltage (OCV) and internal resistance of the cell across varying conditions, is employed to accurately predict the temperature distribution of the cell at different states of charge (SOC). The model also includes scenarios involving high initial cell temperatures to assess their effect on thermal performance during fast charging. To mitigate the thermal stresses generated by these extreme charging conditions, an immersion Battery Thermal Management System (BTMS) is proposed and analyzed. This advanced cooling system is specifically selected to manage the rapid heat generation associated with fast charging. Simulation results confirm the effectiveness of the BTMS in maintaining cell temperatures within safe operational limits, minimizing thermal gradients, and preventing overheating even in the most challenging conditions. Under natural convection cooling, the module temperature reached 368 K at an ambient temperature of 303 K and 396 K at 333 K, emphasizing the need for active cooling solutions to avoid thermal runaway and ensure safety. The lumped heat generation model, validated for a single cell and extended to a 16-cell battery module, demonstrated high computational efficiency and applicability for real-world thermal management scenarios. Immersion cooling systems effectively kept the module temperature below 308 K, with inlet coolant velocities up to 12 m/s required in extreme conditions (333 K), reducing the maximum cell temperature from 397.5 K to below 308 K, achieving a temperature drop of over 89.5 K in less than 45 seconds. The study also found that temperature uniformity was achieved after 0.4 SOC at 303 K. High-speed cooling is essential during the brief charging period (approximately 700 seconds), with high coolant velocities crucial for rapid thermal regulation. These findings provide critical insights into charging strategies and cooling mechanisms, offering a pathway to safer, more efficient, and thermally stable operation in electric vehicles and energy storage systems, even under extreme environmental and operational conditions.</div></div>