Thermal Management of New Energy Vehicles

New energy vehicles (electric vehicles) include cabin, battery, motor and electronic control thermal management. The cabin thermal management system includes air conditioning cooling, heat pump heating or PTC heating, with heating and cooling requirements. The main components include electric compressor, electronic expansion valve, evaporator, condenser, heat exchanger, PTC or heat pump condenser, etc.

The thermal management of motors and electronic controls can be well learned from the thermal management modules of fuel vehicle engines and transmissions, and also uses air cooling and water cooling. Air cooling is mainly used in low-end models with low motor power, while water cooling is mainly used in models with higher power. When working, the coolant is driven by a water pump to circulate in the cooling pipe, and the coolant takes away the heat generated by the motor and electronic control through heat exchange processes such as radiators.

Battery thermal management can be said to be the biggest increment of electric vehicle thermal management. At the same time, since the ambient temperature has a huge impact on the working state of the battery, the quality of battery thermal management is crucial to the user experience of electric vehicles. The efficient working temperature range of power batteries is 20-35℃. Too low temperature (<0℃) will cause the battery activity to decrease, the charging and discharging power performance to decrease, shorten the cruising range, and damage the battery life; too high temperature (>45℃) will not only damage the battery life, but also may cause battery thermal runaway, and even fire and other serious accidents. The internal temperature of the battery and the temperature uniformity between battery modules will also affect the battery performance and cycle life. Therefore, the battery thermal management system requires a complex and sophisticated cooling circuit to maintain the temperature consistency of the battery cells, and can accurately measure and monitor the battery temperature, dissipate heat in time when the battery temperature is too high, and heat quickly when the temperature is too low. At present, there are many ways to manage battery thermal management, such as air cooling, water cooling, direct cooling, and phase change materials.

Liquid cooling is the battery thermal management solution with the best application prospects due to its faster cooling speed and higher heat transfer coefficient (it can be assisted by phase change materials and other technologies). Since the power battery cells are arranged more neatly, the battery liquid cooling is mainly carried out in the form of a liquid cooling plate. The traditional battery liquid cooling plate adopts a whole plate structure and is placed under the battery pack. CATL uses a new layout of adding a liquid cooling plate between two cells in its newly released flagship product, the Kirin battery, which reduces the heat conduction of the two adjacent cells and improves safety, but the amount of liquid cooling plates used in a single vehicle will also increase exponentially.