The aim of this research project was to optimize the thermal dynamic model of battery system design for electric vehicles (EVs) using Computational Fluid Dynamics (CFD) analysis. The primary objective was to develop thermal models for different cooling methods, including natural convection, forced convection, indirect cooling, partial immersion, and full immersion. In addition, several modified models with different geometric configurations were developed based on the previous simulation results. The findings indicate that the new geometric battery system design achieves significant temperature reduction while consuming less coolant compared to conventional approaches. These improvements demonstrate the potential of optimized designs to enhance both efficiency and thermal performance in EV battery systems.