DOI: 10.30518/jav.1959220 ISSN: 2587-1676

Numerical Investigation of the Thermal Behavior of Air-Cooled 26650 Lithium-Ion Battery Modules under Different Cell Arrangements and Discharge Rates

Kaan Süleyman Uz, Merve Şentürk Acar, Fatih Ünal
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The thermal performance of lithium-ion battery modules is a critical design issue for electric and hybrid-electric aviation systems, where safe operation, temperature uniformity, and compact system architecture are essential. In this study, the transient thermal behavior of air-cooled 26650 lithium-ion battery modules was numerically investigated under different cell arrangements and discharge rates. Two battery module configurations, consisting of 25 cylindrical cells, were modelled: an aligned cell arrangement and a staggered cell arrangement. Three-dimensional transient CFD analyses were performed using ANSYS Fluent 2021 R2 under incompressible flow conditions. Forced air cooling was provided at an inlet velocity of 1 m/s, while the battery cells were modelled as equivalent homogeneous solid regions with volumetric heat generation rates corresponding to 1C–5C discharge conditions. The maximum temperature values of the two configurations were very close under identical discharge conditions. However, the staggered arrangement exhibited lower ΔT values, indicating improved temperature uniformity. It also resulted in a slightly higher pressure drop (1.28 Pa) and hydraulic power requirement (0.050 W) than the aligned configuration (1.22 Pa and 0.048 W, respectively), although these increases were negligible compared with the improvement in thermal uniformity. The maximum cell temperature increased from 300.075 K at 1C to 300.774 K at 5C. These findings suggest that passive geometric optimization through cell arrangement improves the thermal uniformity of air-cooled cylindrical battery modules with only a negligible increase in hydraulic power requirement, providing useful design guidance for battery thermal management systems in electric mobility and aviation applications.

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