12v 400ah lithium ion battery pack.What knowledge do you have about cooling lithium batteries?

　　The structural characteristics of lithium-ion batteries have significant differences in thermal conductivity in different directions. The thermal conductivity in the direction parallel to the electrode is significantly higher than that perpendicular to the electrode direction. Therefore, different heat dissipation methods not only have significant differences in efficiency, but also cause serious temperature gradients inside the lithium-ion battery, affecting the distribution of internal current in the battery, This leads to inconsistent internal degradation of the battery, seriously affecting the service life of lithium-ion batteries.

　　There are several main methods for controlling the heat dissipation of lithium-ion battery packs:

　　(1) Utilizing high and low temperature resistant battery materials, including electrodes, electrolyte materials, etc., is a method based on the internal materials of the battery.

　　The battery undergoes chemical reactions, and the components that generate heat are mainly positive and negative electrodes, electrolytes, etc. Therefore, the performance of these materials is studied and improved to increase their temperature activity range. For electrode materials, the key is to improve their thermal conductivity, so that the heat generated inside the battery can be dissipated in a timely manner to avoid accumulating inside the battery and damaging it. In order to improve the thermal conductivity of the electrode, copper and aluminum were added to the electrode carbon material. By improving the thermal stability of battery materials, the capacity of the battery is generally reduced, but the capacity of the battery is an important indicator of the battery. Therefore, improving the thermal performance of battery materials to improve the overall thermal performance of the battery has certain limitations.

　　(2) Using air as a medium

　　Air heat dissipation is the process of air sweeping over the surface of a battery, taking away the heat from the surface. According to the causes of wind, it can be divided into natural convection and forced convection. The wind formed naturally by vehicle speed is called natural convection, and the wind generated forcibly by fans and fans is called forced convection. The ventilation methods are also divided into parallel and serial. Many researchers have found that parallel heat dissipation and ventilation methods are better, but the heat dissipation effect is also affected by the width of the flow channel. Due to limited car space and cost considerations, air cooling is the most widely used. People have studied the effect of parallel heat dissipation based on air cooling, designed various arrangement structures of battery packs, and improved the heat dissipation performance of the wind by designing and improving the windshield, expanding the air duct, and improving the heat dissipation effect. The cost of air cooling is low and the structure is simple, but it is not so effective. When the battery discharge reaches a certain level and the external environment is high, even increasing the wind speed cannot continue to reduce the battery temperature.

　　(3) Using liquid as medium

　　The liquid cooling effect is stronger than air cooling, but the structure is more complex because many liquids cannot come into direct contact with the battery. It is necessary to wrap the liquid, arrange pipelines between the batteries, set up jackets, etc; The liquid that can come into direct contact with the battery generally has poor flow performance and less ideal heat transfer effect. Heat pipe technology, also known as a type of liquid heat dissipation, relies on the phase transition of the medium inside the pipe, which is accompanied by heat absorption and release. This phase transition is mainly a change between liquid and gas, and is an efficient heat exchange element. Its application in battery thermal management is also receiving increasing attention.

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