Types Of Battery Cooling System
Introduction to battery cooling systems
The cooling performance of a power battery has a great impact on the efficiency, service life and safety of the battery. This is due to the fact that the battery generates heat during charging and discharging, resulting in an increase in temperature, which affects many battery characteristics and parameters such as internal resistance, voltage, SOC, available capacity, charge/discharge efficiency and battery life. To achieve the ideal operating temperature for lithium-ion batteries in electric vehicles, active and passive battery thermal management systems (BTMS) are the primary means by which engineers address the issue of overheating and poor battery performance.
The rapid development of new energy vehicle power batteries towards high energy density and high range means that the need for temperature and control of the battery thermal management system has also increased further.
In order to achieve better temperature control, the liquid cooling plate will gradually improve the technical requirements and quality quality, while the value and use of a single vehicle is expected to be greatly enhanced. At the same time, the downstream new energy vehicle industry demand is increasing greatly, the new energy vehicle thermal management system downstream specific categories and models are expected to achieve production scale effect, the product supply chain growth potential is huge.
Battery pack cooling methods
There are three main cooling methods for electric vehicle battery packs: air cooling, liquid cooling and direct refrigerant cooling.
At present, the mainstream cooling is still air cooling, air cooling using air as a heat transfer medium.
There are two common types of air cooling: 1. passive air cooling, which directly uses external air for heat transfer; 2. active air cooling, which can pre-heat or cool the external air before entering the battery system. This type of cooling is easier to achieve and less costly, but the cooling effect is poor. Mainstream miniature electric vehicles such as the Hongguang MINI EV, as well as early hot-selling electric vehicles, all use this method of battery cooling.
Literature References:ACTIVE VS PASSIVE THERMAL MANAGEMENT
Liquid cooling has a better cooling effect. Compared to air cooling, a system using coolant as the medium has tens of times higher specific heat capacity and a higher heat transfer coefficient. And with significantly lower temperatures and temperature differences, battery packs are significantly improved in terms of efficiency, stability and durability. However, liquid cooling places high demands on the hermeticity of the battery pack and can also be more costly.
Refrigerant direct cooling
Direct cooling uses a refrigerant as the heat transfer medium, which absorbs a large amount of heat during the gas-liquid phase change process, increasing the heat transfer efficiency by more than three times compared to refrigerated liquids and removing the heat from the battery system more quickly. However, this system is a dual evaporator system, there is no battery heating, no condensate protection, the refrigerant temperature is not easily controlled and the refrigerant system life is poor.
If you are choosing a cooling solution for your power cell, Trumonytechs recommends liquid cooling as your preferred solution. Although air cooling is currently the mainstream cooling method, the trend of battery development will be towards higher energy density, and the safety of high energy density batteries requires particular attention, as the negative effects of thermal runaway will become increasingly significant.
Liquid-cooled solutions have unique advantages in terms of heat transfer capability, heat transfer consistency, PACK sealing and NVH.
The second reason is that liquid cooling has been used in traditional vehicles for a long time and has a well established supply chain, and the cost of the battery system can be effectively controlled when the design and process are stable.
Liquid cooling solution case
Most mainstream new energy vehicles currently use liquid cooling solutions for thermal management. The following will take Tesla as an example and give a brief insight into how Tesla carries out heat pipe cooling of its battery packs.
Tesla uses liquid cooling solution for battery thermal management, each Tesla is equipped with a special liquid cycle temperature management system, and around each single battery. The coolant used is a mixture of 50% water and 50% glycol and is green in colour.
The coolant flows through pipes and is eventually dissipated in a heat exchanger at the head of the vehicle to maintain a balanced battery temperature, thus preventing localised high temperatures from affecting the battery’s performance. Tesla’s battery thermal management system can control the temperature of the battery pack to ±2°C, effectively controlling the temperature of the battery plates.
The Module water cooling system, for example, is constructed in parallel to ensure that the coolant flowing into each Module is of a similar temperature.
How to reduce complexity and production costs
Liquid cooling solutions are becoming increasingly popular in high-performance computing, gaming, and other industries where there is a need for efficient heat dissipation. The development of liquid cooling solutions involves designing and engineering a system that can efficiently transfer heat from the source to the coolant and dissipate it outside of the system. However, there are some challenges and difficulties associated with developing liquid cooling solutions, which are discussed below:
System complexity: Liquid cooling systems are more complex than traditional air cooling systems, and require additional components such as pumps, radiators, tubing, and coolant. These additional components add complexity to the system, making it more difficult to design and manufacture.
Risk of leaks: Liquid cooling systems are susceptible to leaks, which can cause damage to the components and create safety hazards. Manufacturers must ensure that their designs are leak-proof, and develop protocols to detect and address leaks if they do occur.
Maintenance requirements: Liquid cooling systems require regular maintenance to ensure that they function properly. This includes replacing coolant, cleaning radiators, and checking for leaks. Maintenance can be time-consuming and expensive, and may require specialized tools and knowledge.
Compatibility issues: Not all components are compatible with liquid cooling systems. For example, some motherboards may not have the necessary fittings or mounting points for liquid cooling blocks, or may require additional adapters or brackets. Manufacturers must ensure that their designs are compatible with a wide range of components to ensure that their systems are widely adopted.
Cost: Liquid cooling systems can be expensive to develop and manufacture, due to the additional components and complexity involved. This can make them less accessible to consumers and limit their adoption in the market.
With new energy vehicles driven by a combination of performance and cost requirements, there is a need for power battery liquid cooling plates with light weight, good thermal conductivity, strong anti-corrosion and other fatigue resistance, and excellent process performance. At the same time, under the trend of technology such as fast charging and high range, the battery unit heat generation has increased, which also puts forward higher requirements for battery cooling capacity.