Car Battery Cooling Systems
The working principle of the battery is voltage difference. At high temperatures, the electrons inside will be excited, thereby reducing the voltage difference on both sides of the battery. Because batteries can only work within a specific temperature range. The cooling system needs to be able to maintain the battery pack within a temperature range of approximately 20-40°C while keeping the temperature difference within the battery pack to a minimum (no more than 5°C).
If the internal temperature difference is large, the charge and discharge rate of each cell will be different, thereby reducing the performance of the battery pack. If the battery overheats or the battery pack temperature distribution is uneven, potential thermal stability issues such as capacity fading, thermal runaway, and fire explosion may occur. Faced with life-threatening safety issues, the electric vehicle industry continues to innovate to improve battery cooling systems.
Air-cooling has a simple structure and low cost. Many early cars adopted this battery cooling method. The principle of air cooling is to use natural wind or a hair dryer combined with an evaporator to cool the battery. The battery is preheated in cold weather. An electric heating film is added in the middle of the battery module, making heating and cooling relatively simple.
The shortcomings of air-cooling technology using air as the medium are also quite obvious. Its heat dissipation effect obviously cannot meet the heat dissipation requirements of current new energy vehicles. Moreover, air cooling is greatly affected by the temperature of the outside air. Especially under overheated or overcooled weather conditions, the heat transfer efficiency drops sharply.
In contrast, liquid cooling technology is more relaxed for battery thermal management. At present, some car companies are equipped with liquid-cooled battery systems. The coolant passes through the internal pipes of the battery and takes away the heat generated by the battery during operation. This is the same as water-tank water-cooled fuel vehicles. However, under low temperature conditions, the system will also perform maintenance on the battery pack. heating.
Compared with air, systems using coolant as the medium have dozens of times the specific heat capacity and higher heat transfer coefficient, bringing better cooling effects. After the temperature and temperature difference are significantly reduced, the battery pack’s working efficiency, stability and durability are significantly improved. Of course, liquid cooling systems will also cost more.
The disadvantage of liquid-cooled batteries is that the structure is relatively complex, which increases the weight of the battery pack, making electric vehicles generally weigh more than 2 tons, just like a fully loaded car at all times, affecting performance. On the other hand, it increases the volume of the battery pack and occupies the cabin space. , which is equivalent to reducing the energy density.
Refrigerant direct cooling
The direct refrigerant cooling method makes full use of the refrigerant in the vehicle air conditioning system and introduces it into the internal evaporator of the battery to achieve cooling purposes. The refrigerant direct cooling system mainly consists of the following parts: electric compressor, double evaporators, condenser, double expansion valves, pipelines, and liquid storage dryer.
This refrigerant plate design is simpler, but the advantage is its detachability, and the cooling system can be easily replaced or even repaired. The disadvantage is that it cannot be heated directly and requires a new heating system.