Thermal Management of Li-Ion Battery Systems -Lithium - Ion Battery Equipment
The safety of new energy vehicles has always received great attention, and everyone's concerns are also related to batteries, including fire and explosion, leakage, wading, radiation, and so on. In fact, car companies will take these issues into account when developing new energy vehicles, and will deal with them or make concessions in some respects for safety.
Here, it is important to understand the cooling system of the power lithium battery. The quality of the cooling performance will directly affect the efficiency of the battery, as well as the life and safety of the battery.
During the process of charging and discharging, a power lithium battery will generate a certain amount of heat, which will lead to an increase in temperature. The increase in temperature will affect many characteristic parameters of the battery, such as internal resistance, voltage, available capacity, discharge efficiency, and battery life.(Lithium - Ion Battery Equipment)
In order to prolong the service life of the power lithium battery as much as possible and obtain the maximum power, the battery should be used within the specified temperature range, which involves the cooling system of the power lithium battery.
At present, the thermal management of new energy vehicle power lithium battery systems can be divided into 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 difference in the heat exchange medium.
Free cooling
Natural cooling does not have additional devices for heat exchange. In layman’s terms, it relies on natural wind. For example, BYD Qin, Tang and Tengshi models use LFP cells for natural cooling.
The advantages of natural cooling are simple structure, low cost, small footprint, obvious disadvantages, low heat dissipation efficiency, and cannot meet the cooling requirements of high-power charging and discharging. Generally, it is only used for electric vehicles with moderate operating conditions and sensitive to cost. .
air cooling
In the new energy electric vehicles sold on the market, the proportion of air cooling is still relatively large, and it is the most widely used heat dissipation technology in the power lithium battery of new energy vehicles.
Air cooling uses air as the heat exchange medium. The principle is to use the cooling fan to inhale the air from the interior of the compartment to cool the power lithium battery and the control unit of the power lithium battery. Models like the Toyota Prius, Honda Insight, Camry Hybrid and Corolla Twin Engine all use air-cooled battery cooling systems.
Compared with other technologies, the air-cooling technology is relatively simple and convenient for safety maintenance, and can achieve good heat dissipation performance at a low cost.
However, the disadvantages of air cooling technology are also very clear, especially compared with liquid cooling technology, the heat exchange coefficient between it and the battery surface is low, the speed of cooling and heating is still relatively slow, and the average temperature inside the battery box is not easy to control. , and the sealing design of the battery box is difficult, and the dustproof and waterproof effect is poor. It has to be said that some electric vehicle fire incidents are due to the poor thermal management performance of air-cooled technology.
liquid cooling
With the increasingly high requirements for power lithium batteries in the use environment, liquid cooling technology has gradually replaced air cooling technology and has become the preferred choice of major car companies. Especially in large and medium-sized pure electric vehicles, the utilization rate of liquid cooling system is very high. High, there are more and more new models using liquid cooling in small pure electric vehicles and even plug-in hybrid vehicles.
The principle of liquid cooling technology is to take away the heat generated by the battery during operation through the cooling liquid inside the battery pack, so as to achieve the effect of reducing the battery temperature.
To put it simply, the liquid cooling system technology passes through a water pipe in the battery pack. When the battery is to be cooled, cold water is poured into the water pipe, and the heat is taken away through the cold water to cool down, and when the temperature is to be heated, hot water is passed into the water pipe .
The temperature control effect of the liquid cooling system on the battery pack is better than that of the air cooling system. The liquid medium has a high heat transfer coefficient, a large heat capacity and a faster cooling speed.
Here, it is important to understand the cooling system of the power lithium battery. The quality of the cooling performance will directly affect the efficiency of the battery, as well as the life and safety of the battery.
During the process of charging and discharging, a power lithium battery will generate a certain amount of heat, which will lead to an increase in temperature. The increase in temperature will affect many characteristic parameters of the battery, such as internal resistance, voltage, available capacity, discharge efficiency, and battery life.(Lithium - Ion Battery Equipment)
In order to prolong the service life of the power lithium battery as much as possible and obtain the maximum power, the battery should be used within the specified temperature range, which involves the cooling system of the power lithium battery.
At present, the thermal management of new energy vehicle power lithium battery systems can be divided into 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 difference in the heat exchange medium.
Free cooling
Natural cooling does not have additional devices for heat exchange. In layman’s terms, it relies on natural wind. For example, BYD Qin, Tang and Tengshi models use LFP cells for natural cooling.
The advantages of natural cooling are simple structure, low cost, small footprint, obvious disadvantages, low heat dissipation efficiency, and cannot meet the cooling requirements of high-power charging and discharging. Generally, it is only used for electric vehicles with moderate operating conditions and sensitive to cost. .
air cooling
In the new energy electric vehicles sold on the market, the proportion of air cooling is still relatively large, and it is the most widely used heat dissipation technology in the power lithium battery of new energy vehicles.
Air cooling uses air as the heat exchange medium. The principle is to use the cooling fan to inhale the air from the interior of the compartment to cool the power lithium battery and the control unit of the power lithium battery. Models like the Toyota Prius, Honda Insight, Camry Hybrid and Corolla Twin Engine all use air-cooled battery cooling systems.
Compared with other technologies, the air-cooling technology is relatively simple and convenient for safety maintenance, and can achieve good heat dissipation performance at a low cost.
However, the disadvantages of air cooling technology are also very clear, especially compared with liquid cooling technology, the heat exchange coefficient between it and the battery surface is low, the speed of cooling and heating is still relatively slow, and the average temperature inside the battery box is not easy to control. , and the sealing design of the battery box is difficult, and the dustproof and waterproof effect is poor. It has to be said that some electric vehicle fire incidents are due to the poor thermal management performance of air-cooled technology.
liquid cooling
With the increasingly high requirements for power lithium batteries in the use environment, liquid cooling technology has gradually replaced air cooling technology and has become the preferred choice of major car companies. Especially in large and medium-sized pure electric vehicles, the utilization rate of liquid cooling system is very high. High, there are more and more new models using liquid cooling in small pure electric vehicles and even plug-in hybrid vehicles.
The principle of liquid cooling technology is to take away the heat generated by the battery during operation through the cooling liquid inside the battery pack, so as to achieve the effect of reducing the battery temperature.
To put it simply, the liquid cooling system technology passes through a water pipe in the battery pack. When the battery is to be cooled, cold water is poured into the water pipe, and the heat is taken away through the cold water to cool down, and when the temperature is to be heated, hot water is passed into the water pipe .
The temperature control effect of the liquid cooling system on the battery pack is better than that of the air cooling system. The liquid medium has a high heat transfer coefficient, a large heat capacity and a faster cooling speed.
