The dynamic performance of battery electric vehicles (BEV) is affected by battery output power, which depends on state of charge (SOC) and the temperature of battery cells. The temperature of the batteries varies in particular with the environment, in which the user stores the vehicle, and the battery output power. It is therefore necessary to employ thermal management systems that can control the battery temperature within the optimal range under severely hot and cold conditions in BEVs.
A highly sophisticated thermal management system and its operation strategy were developed to fulfill the above requirements. The powertrain components to be thermo-controlled were located into two coolant circuits having different temperature range. The compact and efficient front-end heat exchangers were designed to optimally balance the cooling performance of powertrain, cabin comfort, vehicle aerodynamics and the vehicle design. The battery pack was optimally thermo-controlled by precisely controlling two 3-way valves in all driving and environmental conditions. To reduce the temperature variation between battery cells, the coolant passage including cooling plates in the battery pack were designed so that the coolant was homogeneously distributed into all battery modules. The pre-conditioning system of the battery, which controlled its temperature before driving by using telematics, were added to the thermal management system. It was clarified that this system significantly enhanced the driving range at low ambient temperature conditions.
The developed system including control strategy realized that Honda’s small BEV demonstrated high dynamic and energy-efficient performance under all environmental conditions.