The composition and design process of thermal management system for power lithium-ion battery

The composition and design process of the thermal management system for power lithium-ion batteries. Power lithium-ion batteries are the source of energy for electric vehicles. During the charging and discharging process of the battery, a certain amount of heat will appear in the battery itself, which will cause the temperature to rise, which will affect the working characteristics of many batteries, such as internal resistance, voltage, SOC, usable capacity, charge and discharge power and battery life. The thermal effect of the battery will also affect the function and cycle life of the car. Therefore, heat treatment of the function of the battery is very important to the driving life of the car. Next, communicate with us in terms of the planning process of the battery heat treatment system, the type and selection of parts, and the function and verification of the heat treatment system: 01 It is necessary to heat the power lithium ion battery. 1. The battery heat generation is due to the impedance of the battery During the charging and discharging process of the battery, current flows through the battery, causing heat to appear inside the battery. Otherwise, there will be a certain amount of heat due to the electrochemical reaction inside the battery. 2. The influence of temperature rise on battery life The rise in temperature has an effect on the calendar life and cycle life of the battery. Click to view the picture and talk about it. Click to view the picture and talk about it. As can be seen from the above two pictures, temperature has a great influence on the calendar life of the battery. Regarding the same battery, when the ambient temperature is 23°C, the remaining capacity of the battery after 6238 days is 80%, and at 55°C, the remaining capacity of the battery after 272 days is 80%. When the temperature is increased by 32°C, the calendar life of the cell is reduced by more than 95%. Therefore, temperature has a greater impact on calendar life, and the higher the temperature, the more serious the decline in calendar life. Click to view the picture and talk about it. Click to view the picture and talk about it. As can be seen from the above two pictures, temperature also has a great influence on the cycle life of the battery. Regarding the same type of battery, when the remaining capacity is 90%, the output capacity at 25°C is 300kWh, while the output capacity at 35°C is only 163kWh. When the temperature rises by 10°C, the cell cycle life is reduced by nearly 50%. Therefore, temperature has a great influence on the cycle life of the battery. Therefore, in order to optimize the function of the battery pack, a heat treatment system needs to be planned to ensure that each battery runs under a reasonable temperature plan. 02 Classification and analysis of heat treatment systems Different heat treatment systems, different types of parts structure, different weights, and different system costs and control methods make the functions of the system different. There are five important categories: Click to view the picture and talk about it 1. Direct cooling system Click to view the picture and talk about it. The direct cooling system has the advantages of compact system, light weight, and good performance. But this system is a double evaporator system, the system has no battery heating, no condensation protection, the refrigerant temperature is not easy to control, and the refrigerant system has a short life. 2. Low temperature radiator cooling system Click to view the picture and talk about it. The low temperature radiator cooling system is an independent system of the battery, which consists of a radiator, a water pump and a heater. The cooling system has the advantages of simple system, low cost, low ambient temperature, economy and energy saving. However, this system has shortcomings such as low cooling function, high water temperature in summer, and utilization of climate constraints. 3. Direct cooling water cooling system Click to view the picture and talk about it. The direct cooling water cooling system has the advantages of compact system, good cooling function, and extensive industrial application planning. However, the part of the system is much colder than direct cooling, the system is chaotic, fuel economy is poor, and the compressor load is high. This type of cooling system is one of the most commonly used battery heat treatment systems. 4. Air-cooled/water-cooled hybrid cooling system Click to view the picture and talk about it. The air/water cooling system has two key parts: 1) water-cooled battery cooler; 2) air-cooled battery radiator. The air-cooled/water-cooled hybrid cooling system has the advantages of compact system, good performance, economy and energy saving in low temperature environment. But the system is chaotic, costly, control chaotic, and reliability requirements high. 5. Direct air cooling system Click to view the picture and talk about it. This system uses low temperature cockpit air to cool the battery. Disclaimer: Some pictures and content of articles published on this site are from the Internet. If there is any infringement, please contact to delete. Previous post: A simple analysis of the characteristics of lithium iron phosphate batteries