Immersion cooling technology is regarded as the optimal choice to meet the stringent thermal management requirements of future high-energy density battery packs. In this study, a module composed of 48 high-nickel ternary lithium-ion batteries, each with a capacity of 175 Ah, totaling 30.7kWh, was selected as the research subject. The total heat generation during 3C charging was 8.64kW. The high-performance side cooling plate BTMS was chosen as the benchmark, which, under severe conditions of an initial temperature of 40°C and an inlet flow rate of 4.45L/min, nearly met the cooling demands during 3C fast charging, with a safe operating time of 694 seconds. Due to the significantly lower density, specific heat capacity, and thermal conductivity of the dielectric fluid used for immersion cooling compared to the water-glycol used for the side cooling plate, the basic immersion cooling BTMS, which has a flow structure similar to that of the side cooling plate BTMS, actually reduced cooling performance under the same conditions, decreasing the safe operating time by approximately 26.22%. Assuming 3C CC charging lasts for 20 minutes, the maximum temperature and temperature difference at the end of charging for the module using basic immersion cooling increased by 20.34% and 220.45%, respectively. The only advantage of the basic immersion cooling BTMS is its significantly lower pressure drop of 0.32 kPa, compared to the side cooling plate BTMS's pressure drop of 6.25 kPa. Further research is required to enhance the thermal management performance of immersion cooling in large module applications.