The charging and discharging process of electric vehicle power batteries generates a large amount of heat, and the development of an efficient heat dissipation design is conducive to improving the efficiency and safety of the battery packs. A combination of cold plate and battery packs is used for the liquid cooling heat dissipation design of the battery packs. The critical maximum temperature is set to 50°C here and the results show that the average battery temperature is lowest and the temperature uniformity is better when the cold plate and battery packs are arranged in a side-to-side lateral direction. The minimum required mass flow rate is 0.05 kg/s for the inter-phase lateral model, while the inter-phase upward model has the lowest pressure drop. Therefore, a structure with an interphase arrangement of power battery and cold plates can be preferred for the thermal design of the battery packs.