The transportation sector is undergoing a significant transformation with the increasing adoption of electric vehicles (EVs). A critical challenge in the revolution of EVs is the effective thermal management of the power generation systems, particularly the batteries, where temperature control is essential for maintaining battery health and performance. This study focuses on optimizing an air-cooled Battery Thermal Management System (BTMS), a popular choice due to its simplicity and cost-effectiveness. Specifically, the research investigates an air-cooled battery pack design comprising 18,650 cylindrical cells arranged in a 6S4P configuration (six series cells and four parallel rows). The study employs unsteady Reynolds-Averaged Navier Stokes (uRANS) methods for 3D and 2D Computational Fluid Dynamics (CFD) simulations to optimize peak temperature, temperature gradient (ΔT), and pressure drop of the pack. By introducing a variable longitudinal pitch and maintaining a constant transverse pitch, the optimization strategy effectively addresses the challenges of peak temperature and pressure drop reduction in the battery pack. The maximum temperature is reduced by approximately 3 K from the baseline design. Furthermore, ΔT is lowered by 21%, pressure drop comes down by 41%, and volume shrinks by 3.5%, promoting a more uniform thermal environment that enhances the battery pack’s overall health and longevity. Additionally, by converting the 3-D designs into 2D models, the study significantly reduced the computational demands while maintaining accuracy.