Bio-based phase change material for enhanced thermal management of batteries under different discharge rates and high ambient temperatures

• Numerical simulation on a Lithium-ion battery module. • Battery thermal management of Lithium-ion batteries with different phase change materials. • Influence of high ambient temperature. • Influence of different discharge rates. • Importance of bio-based phase change material. Maintaining electric vehicle (EV) batteries within a safe operating temperature range is essential to ensure optimal performance and extended lifespan. Passive thermal management using Phase Change Materials (PCMs) provides a reliable and energy-efficient method for achieving near-safe operation; however, their inherently low thermal conductivity limits effectiveness. As tropical regions typically experience ambient temperatures of 24–27 °C, which may rise above 40 °C in certain areas, the present study investigates the thermal safety of lithium iron phosphate (LiFePO 4 ) batteries under elevated ambient conditions of 30, 35, and 38 °C under discharge rates of 3C, 6C, and 8C. Both organic and inorganic PCMs with a thickness of 4 mm are examined, with a focus on bio-based lauric acid, which demonstrates the most favourable thermal performance. To enhance heat dissipation, 0.5 mm and 1 mm copper sheets are incorporated as thermal conductivity enhancers, effectively reducing the peak temperature of a four-cell battery module. Increasing the convective heat transfer coefficient from 30 to 100 W/m 2 ·K further improved thermal regulation. The combined use of enhanced-conductivity PCMs and optimised cooling configurations (box and series type) proved effective, even at an ambient temperature of 38 °C. Results confirm that safe battery operation can be achieved without forced convection. A temperature reduction of approximately 17.6 % is observed with the best thermal management strategy. Simulations with a bio-PCM layer embedded with a 1 mm copper sheet showed higher liquid fractions and improved heat dissipation, demonstrating that hybrid PCM-based systems provide superior thermal regulation and operational safety for LiFePO 4 batteries in high-ambient-temperature environments.