This study developed a simulation model for the liquid-cooled thermal management system of power batteries. We designed multiple liquid-cooled plate schemes to investigate the effects of key parameters—including the number of flow paths, fluid flow direction, flow path width, flow path depth, inlet flow velocity, and stamping R-radius—on the heat dissipation performance, temperature uniformity, and system energy consumption of battery modules under a 2C discharge rate. Results revealed that fluid flow direction and flow path width significantly influenced the heat dissipation performance of the battery module. Under fluid direction I, the maximum and average temperatures were 2.16 °C and 2.15 °C lower than those under direction II. Increasing the flow path width from 10 mm to 16 mm reduced the maximum temperature by 2.07 °C and the average temperature by 2.33 °C. The maximum temperature difference under direction II was 0.87 °C lower on average than under direction I, while increasing the inlet flow velocity from 2 L/min to 10 L/min increased the pressure drop by 90.17%.