With the growing demand for electric vehicles (EVs), ensuring the safety and efficiency of battery systems is critical. This paper presents a methodology integrating 3D Finite Element Methods (FEM) and Computational Fluid Dynamics (CFD) to analyze battery systems, effectively mitigating thermal runaway phenomena. By combining FEM and CFD, our methodology provides a comprehensive approach to assess thermal management strategies within battery systems. This integration enables engineers to accurately simulate thermal behavior, predict hotspots, and optimize cooling strategies, thereby mitigating the risk of thermal runaway. Furthermore, our methodology minimizes the reliance on costly and time-intensive physical prototypes and testing. By leveraging virtual simulations, engineers can rapidly iterate through design modifications, assess their impact on thermal performance, and make informed decisions early in the development process. This article demonstrates the efficacy and accuracy of our methodology in analyzing battery systems for electric vehicles. Using Simcenter STAR-CCM+, temperature profiles were analyzed focusing on critical thresholds during the use of a battery pack in an extreme condition. In parallel, finite element analysis via Simcenter 3D indicated thermal stresses leading to catastrophic failure of battery packs. By looping this cycle, it is possible to iteratively define safe and efficient designs. Overall, our approach offers a significant advancement in battery development, facilitating faster and more cost-effective design iterations while ensuring enhanced safety and reliability of EV battery systems.