Coupled Effects of Phase Change Material and External Convective Cooling on an IP67‐Compatible 13s7p Li‐Ion Battery Pack: A Numerical Study

ABSTRACT Efficient thermal management of lithium‐ion battery (LIB) packs is critical for enhancing cell performance, safety, and service life, especially in compact battery systems used in electric two‐wheelers. While phase change material (PCM)‐based battery thermal management systems (BTMS) offer high latent heat absorption with low energy consumption, most existing hybrid PCM–air cooling strategies rely on direct airflow through inter‐cell gaps, which are impractical for sealed battery enclosures. Sealed battery packs for electric two‐wheelers must satisfy ingress‐protection requirements, which restrict the use of direct airflow through inter‐cell passages. To address this constraint, the present study proposes and evaluates an IP67 (Ingress Protection‐67) compatible hybrid battery thermal management configuration in which convective cooling is applied only at the external casing surfaces while the inter‐cell spaces are fully occupied by PCM. A three‐dimensional transient numerical model of a 13s–7p LIB pack is developed using ANSYS Fluent and validated experimentally for natural convection (NC) and PCM+NC. The numerical results for four configurations—NC, forced convection (FC), PCM + NC, and PCM + FC—are systematically compared over discharge rates ranging from 0.75 C to 1.5 C. The results demonstrate that FC maintains the maximum cell temperature ( T max ) below 40°C over a greater depth of discharge (DOD) than NC. In comparison, the PCM‐filled battery pack sustains T max below 40°C at 0.75 C and at significantly higher DODs and C ‐rates than both NC and FC. Moreover, integrating PCM with either NC or FC effectively prevents T max from exceeding the critical threshold of 50°C. Among all configurations, at 1.5 C, PCM + NC reduced the maximum temperature difference to 2.11°C, which is 49.6% less than the baseline PCM + NC case. However, incomplete PCM melting even at high C ‐rates indicates underutilization of latent heat capacity and highlights the need for further optimization. Furthermore, strong agreement between numerical predictions and experimental data confirms the effectiveness of PCM‐convective cooling integrated model in regulating LIB pack temperatures.