Why do car power lithium battery packs need a cooling system? Bonnen engineer gives the insights below.
1. The function of the cooling system of the power lithium battery pack for vehicles is to maintain a better working temperature of the power battery by cooling or heating the power battery to improve its operating efficiency and extend the life of the power battery.
2.Analysis from the basic principle of battery charging and discharging. We know that battery charging actually supplements the electrons inside the battery while discharging consumes the electrons inside the battery. Both charging and discharging will be accompanied by the violent movement of electrons. The thermal effect and this thermal effect is unavoidable unless there is no electronic movement inside the battery, but this is impossible.
Nowadays, the thermal management of vehicle power lithium battery systems has four categories: natural cooling, air cooling, liquid cooling, and direct cooling. Among them, natural cooling is a passive thermal management method, while air cooling, liquid cooling, and DC are active. The important difference between the three is the heat exchange medium.
Natural cooling Natural cooling has no additional devices for heat exchange. For example, BYD uses natural cooling on models that use LFP batteries such as Qin, Tang, Song, E6, and Tengshi.
Air cooling Air cooling uses air as a heat exchange medium. There are two common types. The first type is called passive air cooling, which directly uses external air for heat exchange. The second type is active air cooling, which can heat or cool the outside air before entering the battery system. Many early Japanese and Korean electric vehicle models used air cooling.
Liquid cooling Liquid cooling uses antifreeze (such as ethylene glycol) as the heat exchange medium. In the method, there are generally multiple different heat exchange circuits. For example, VOLT has a radiator circuit, an air conditioning circuit, and a PTC circuit. The battery management system responds to adjustment and switching according to the thermal management strategy.
Direct cooling Direct cooling uses refrigerant as the heat exchange medium. The refrigerant can absorb a large amount of heat during the gas-liquid phase change process. Compared with the refrigerant, the heat exchange efficiency can be increased by more than three times, and the battery system can be quickly replaced. Heat away. The direct cooling system has the advantages of a compact system, lightweight, and good performance. However, this system is a dual evaporator system, the system has no battery heating, no condensate protection, the refrigerant temperature is not easy to control, and the refrigerant system has a poor life.
Summary: The cooling performance of the power battery directly affects the efficiency of the battery, and also affects the battery life and safety of use. Therefore, the safety performance requirements of the electric vehicle power lithium battery cooling system are strict. When choosing the electric vehicle power battery cooling system, we must pay attention to quality and protection devices to choose.