It is well known that thermal management is a key factor in design and performance analysis of Lithium-ion (Li-ion) battery, which is widely adopted for hybrid and electric vehicles. In this paper, an air cooled battery thermal management system design has been proposed and analyzed for mild hybrid vehicle application. Computational Fluid Dynamics (CFD) analysis was performed using CD-adapco's STAR-CCM+ solver and Battery Simulation Module (BMS) application to predict the temperature distribution within a module comprised of twelve 40Ah Superior Lithium Polymer Battery (SLPB) cells connected in series. The cells are cooled by air through aluminum cooling plate sandwiched in-between every pair of cells. The cooling plate has extended the cooling surface area exposed to cooling air flow. Cell level electrical and thermal simulation results were validated against experimental measurements. Thermal behavior of the battery module under constant-current (CC) discharge and dynamic drive cycle electrical-load cases were studied to ensure adequate cooling required for satisfying the specified operating temperature range. For the proposed design, the maximum temperature gradient within each cell has been found to be 1.4°C during the US06 cycle. The results of this study also demonstrate that fully coupled electrical-thermal three-dimensional CFD modeling approach can be a very useful design tool for “off-line calibration” of higher fidelity dynamic battery thermal models suitable for control applications such as in EcoCAR competitions these authors participating in.