The battery pack is the core energy source of new energy vehicles, providing driving power for the entire vehicle. It mainly forms the main body of the battery pack through the shell envelope. The design of the power battery system must meet the power requirements and other designs of the vehicle. At the same time, the internal structure, safety and management design of the battery system itself must be considered. As the carrier of the battery module, the battery pack shell plays a key role in the safe operation and protection of the battery module. The battery casing is the carrier of the power battery of new energy vehicles. It is generally installed in the lower part of the car body and is mainly used to protect the lithium battery from damage when it is impacted and squeezed by the outside world. Traditional vehicle battery boxes are cast from steel plates, aluminum alloys and other materials. The surface is then spray-coated. With the development of automobile energy conservation, environmental protection and lightweight, battery case materials have also appeared in a variety of lightweight material options such as glass fiber reinforced composite materials, SMC sheet materials, carbon fiber reinforced composite materials and so on. Steel casing. Steel battery pack casing is the most original power battery pack casing material and is generally welded by cast steel plates. High strength, high rigidity and heavy quality. The surface needs to be treated with anti-corrosion so that it can still have a good anti-corrosion effect under long-term high temperature conditions. Aluminum alloy shell. Automotive power battery packs are made of aluminum alloy materials, which have the characteristics of easy processing and molding, high temperature corrosion resistance, good heat transfer and electrical conductivity. The aluminum alloy shell (except the shell cover) can be stretched and formed in one step. Compared with stainless steel, the welding process of the box bottom can be omitted. During welding, there will be no problems such as a decrease in cold wind quality due to burning of metal elements during welding. In addition, aluminum alloy shells have the following four major advantages. (1) Long service life. The simulated aging test of the aluminum alloy shell shows that its service life is more than 20 years, far exceeding traditional materials such as metal. (2) Flame retardant, smoke-free and non-toxic. The flame retardancy level of aluminum alloy materials can reach FV0, and the smoke level under high temperature burning can reach level 15. The smoke is non-toxic and the toxicity level is ZA1 (quasi-safety level one). (3) Explosion-proof performance. The aluminum shell cover of the power battery is specially equipped with an explosion-proof device. When the internal pressure of the battery cell is too high, the explosion-proof device will automatically open to release the pressure to prevent explosion. (4) Anti-aging performance. Among metal materials, aluminum has excellent anti-aging properties. The anti-aging performance test shows that the maximum aging thickness on the surface is less than 50 μm in 20 years depending on the location of use and the climate zone. The minimum thickness of most cabinets is 5mm, which is less than 1% of the cabinet thickness, so it has no obvious impact on the mechanical properties of the cabinet. SMC conforms to the material. That is, sheet molding compound, the main raw materials are composed of GF (special yarn), UP (unsaturated resin), low shrinkage additives, MD (filler) and various additives. New energy battery shell deep drawing forming technology carbon fiber reinforced composite materials is one of the effective ways to solve the lightweight development of automobiles. At present, carbon fiber composite materials have become an ideal substitute for traditional metal battery boxes. Compared with metal materials, the density of carbon fiber is approximately 1.7g/cm3. Tensile strength 3000MPa, elastic modulus 230GPa, light weight, high strength, high temperature resistance, friction resistance, earthquake resistance, low thermal expansion coefficient. Recently, CCTV's "Great Powers, Weapons" broadcast the CATL new energy battery production line. Today, I will lead you into the factory of CATL, China’s power battery unicorn, and explore the birth story of a super battery. This is China's largest power battery production base. The batteries produced every day can meet the needs of 1,500 electric vehicles. Each vehicle's battery pack consists of 150 to 300 such cells. China also leads the world in these battery testing equipment. 500-degree high-temperature fire, water immersion, spraying, and falling from high altitudes are all subject to the highest international standards. Even the 8 mm steel needle is not considered to be too strict internationally and does not require rigid regulations. The artificial short-circuit simulation test of piercing three battery cells was not sloppy here either, and all tests passed. BMW X1 and new 5 series battery cells are the first domestic and world-class automated production line. Cell is the smallest unit of a battery system. M cells form a module, and N modules form a battery pack. This is the basic structure of a vehicle power battery.

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