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Analysis of 3 technical routes of power battery cooling system

  • Categories:Industry News
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  • Time of issue:2020-04-03 14:22
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Analysis of 3 technical routes of power battery cooling system

(Summary description)Analysis of 3 technical routes of power battery cooling system...

  • Categories:Industry News
  • Author:
  • Origin:
  • Time of issue:2020-04-03 14:22
  • Views:
Information

 

  The cooling performance of the power battery directly affects the efficiency of the battery, and also affects the battery life and safety. Because the battery itself generates a certain amount of heat during the charge and discharge process, which causes the temperature to rise, and the temperature increase will affect many characteristics of the battery, such as internal resistance, voltage, SOC, available capacity, charge and discharge efficiency, and battery life.

  In electric vehicles, the cooling system is mainly divided into two parts: one is to cool the drive motor, vehicle controller and DC / DC of the power system, and the other is to cool the power battery and on-board charger of the power supply system. This article discusses power battery cooling systems.

 

 

  At present, electric vehicle power batteries are lithium-ion batteries. The performance of lithium-ion power batteries is more sensitive to temperature changes, the loading space on vehicles is limited, the number of batteries required by vehicles is large, and the batteries are closely connected. When the vehicle is running under different driving conditions such as high-speed, low-speed, acceleration, and deceleration, the battery will be discharged at different rates and generate a large amount of heat at different heat generation rates. In addition, time accumulation and space effects will cause uneven heat accumulation. As a result, the operating temperature of the battery pack is complicated and changeable.

  The cooling performance of the power battery directly affects the efficiency of the battery, and also affects the battery life and safety. Because the battery itself generates a certain amount of heat during the charge and discharge process, which causes the temperature to rise, and the temperature increase will affect many characteristics of the battery, such as internal resistance, voltage, SOC, available capacity, charge and discharge efficiency, and battery life.

 

 

  In order to make the battery pack exhibit the best performance and longevity, it is necessary to optimize the structure of the battery pack, thermally manage it, increase heat dissipation facilities, and control the temperature environment of the battery operation.

 

  Main cooling scheme

  Different thermal management systems, different types of components, different structures, different weights, different system costs, and different control methods make the performance of the systems different. When designing the type of battery pack thermal management system, it is necessary to consider the cooling performance requirements of the battery, combined with the performance of the vehicle and the size of the space, the stability and cost of the system are also factors to be considered.

 

  Working instructions for different cooling systems

  1.Air-cooled

  There are the following cooling methods for electric vehicle battery packs at home and abroad: air cooling, liquid cooling, and heat pipe cooling. At present, the air cooling method is still the main method. Air cooling is relatively easy to achieve, but the cooling effect is not good.

 

Schematic diagram of typical air cooling system

 

  Liquid cooling

  Liquid cooling has a better cooling effect and can make the temperature distribution of the battery pack uniform. However, liquid cooling has high requirements for the tightness of the battery pack. If a conductive liquid such as water is used, the liquid and battery cells need to be sealed with a water jacket. Body separation, which not only increases the complexity of the system but also reduces the cooling effect.

  Generally, the cooling system is installed near the battery module. The principle is similar to the cooling principle of the air conditioner. The cooling system is connected to a single battery module through a pipe. The heat is taken away, the cooling system cools the glycol, and the excess heat is discharged to the outside through the fan, and the glycol is recycled into the battery module again to continue to absorb the heat emitted by the battery.

 

 

 

Schematic diagram of a typical liquid cooling system

 

  3. Heat pipe technology

  Heat pipe technology can meet the requirements of high temperature heat dissipation and low temperature preheating of the battery pack. It has fast response and good temperature uniformity. After the new cooling method of the battery pack was proposed, it has developed to a certain extent and has become the focus of industrial research However, due to layout and volume limitations, there are currently no actual cars in use.

 

Heat pipe technology work diagram

 

  From the perspective of current electric vehicle power battery cooling methods, air cooling has always occupied a major position, especially Japanese electric vehicles, which basically use air cooling systems. As the application environment requires more and more batteries, liquid cooling has also become a priority solution for car companies, such as Tesla, BMW and other brands. China's mainstream electric passenger car companies have also begun to switch to liquid cooling systems. From the medium and long-term trend, liquid cooling will occupy the mainstream.

 

  Main components of battery pack cooling system

  Different cooling systems have corresponding cooling components: the main components of the air cooling system are fans, and the main components of the liquid cooling system are cooling plates.

  Air cooling system components: cooling air duct, fan, resistance wire

  The selection of the fan directly affects the cooling effect of the battery pack air cooling system. The selection requirements of the fan are as follows: determine the air flow according to the heat generation rate of the battery; meet the temperature rise requirements of each module; select the fan that meets the requirements based on the required air flow of the system and the pressure drop curve of the system.

  Liquid cooling system components: water-cooled pipes, cooling pumps, cooling valves, cooling plates

  As one of the most critical components in the battery pack liquid cooling system, the cooling plate selection is very important. The selection of the cooling plate must meet the following requirements: the pressure drop of the cooling plate must meet the customer requirements; the consistency of the cooling water flow requirements; the burst pressure requirements; the mechanical requirements of the cooling plate; the cooling plate must pass the vibration and shock load tests; the cooling plate Must meet tolerance requirements and space requirements.

  There are many manufacturers of battery cooling system components, and most of the main components are provided by traditional electrical companies. At present, battery management system companies and PACK assembly companies also involve the production of customized products.

 

——From the list of cars

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