In this paper, the cooling system of a two-dimensional lithium-ion battery pack with 9 battery cells is simulated. The airflow at the Reynolds number range from 80 to 140 flows through the cooling system. In this analysis, the temperature of all 9 battery cells is examined separately. The amount of pressure drop and temperature of the cooling system is assessed. Another geometry variable is the size of the inlets and outlets, which are changed simultaneously between 0.1 and 0.2. The finite element method is used for the simulations. The findings suggest that increasing the Reynolds number lowers the battery pack's maximum temperature. At a Reynolds number of 80, increasing the input temperature raises the maximum temperature of all the battery cells except the one in the battery. In model 6, this increase has increased the maximum temperature by more than 40%. Increasing the intake size raises the maximum temperature of all battery cells at other Reynolds numbers. The battery cell located at the inlet has the minimum, and the battery cell located at the outlet side has the maximum temperature. An enhancement in the Reynolds number and inlet size intensifies the pressure drop in the cooling system.