A thermal management system for a battery pack having a conductive cooling plate and battery cells includes a compressor, flow control valves, temperature sensor(s), and a controller. The compressor circulates refrigerant through the plate to cool the cells. The temperature sensor measures a temperature of the battery pack. The controller is programmed to receive the temperature from the temperature sensors and selectively transmit switching control signals to the valves to command a change in direction or flow of the refrigerant through the cooling plate. This limits a temperature variance between the battery cells over time. A vehicle includes a transmission, an electric traction motor, a battery pack, and the thermal management system noted above. A method includes receiving the temperature, transmitting switching control signals to the valves, and controlling a flow of refrigerant through the plate via the valves in response to the switching control signals.