Development and revitalization of battery case

1. Battery case production surges
2. Battery case industry development trend
3. Welding technology of battery case
4. China’s battery case development technology is advanced

The battery case is a new increment in the new energy vehicle, and it is a structural part to ensure the safety of the battery cells. According to forecasts, the world battery case market space is expected to reach 40.4 billion RMB in 2025, with a compound growth rate of 46.9%.

Battery case production surges

The battery case is a brand new addition in new energy vehicles. Compared with traditional fuel vehicles, the power transmission system of pure electric vehicles is greatly optimized after omitting the engine. Traditional automobiles generally use a structure with a front-mounted engine and a rear-mounted drive at the same time, which inevitably requires a transmission mechanism to transmit power.

The pure electric vehicle is driven by a motor, and the placement of the motor can be flexibly adjusted according to the model, thus eliminating the need for a transmission mechanism. The battery case is the carrier of the power battery of the new energy vehicle. It is generally installed at the lower part of the vehicle body and is mainly used to protect the lithium battery from being damaged when it is collided or squeezed by the outside world.

The battery case is the “skeleton” of the battery pack and an important safety part. The battery case structure system is mainly composed of the battery pack upper cover, tray, various metal brackets, end plates and bolts. dustproof). Among them, the lower box of the battery case (that is, the battery tray) bears the quality of the entire battery pack and its own quality, and resists external impacts to protect the battery modules and cells. It is an important safety structure for electric vehicles.

Due to the need for lightweight, battery case materials have evolved from steel to aluminum. Among the main components of the battery pack, the battery cell body has the highest quality, followed by the lower box body, upper cover, and BMS integrated components of the pack. The battery pack casing is the most primitive power battery pack casing material, generally welded by cast steel plates, with high strength, high rigidity and heavy weight. At present, aluminum alloy battery case are mostly used, which greatly reduces the weight compared with steel.

Battery case industry development trend

The battery case industry is an asset-heavy industry characterized by low fixed asset turnover and gross profit margins that are greatly affected by capacity utilization. We classify the Changjiang Passenger Vehicle Parts Index and divide it into ten sub-sectors: gearbox, stamping parts, chassis structural parts, engine, wheel hub, interior and exterior trim, automotive electronics, lightweight, thermal management and general parts.

Stamping parts, lightweight parts and chassis structural parts are similar in nature to the battery case. They are all made of metal and deformed into usable materials through a certain processing process.

The battery case is bulky and heavy, so it is necessary to build a factory nearby with the OEM or battery manufacturer. According to the dismantling data of Tesla Model 3, the weight of the box under the battery case is 29.5KG, accounting for 6.2% of the battery cell, so it needs to be matched near the OEM. Major Chinese battery case companies such as Lingyun and Minth have established factories near the supporting OEMs.

Adopting the upstream and downstream integration strategy can greatly reduce the cost. For the battery case industry, aluminum alloy profiles are the core raw materials for welding. Opening up the upstream can save costs on the one hand, and meet the development requirements of the industry on the other hand.

At present, the mainstream aluminum profiles use ordinary 6063 or 6016, and the tensile strength is basically between 220 and 240 MPa. If you can use extruded aluminum profiles with higher strength, such as Constellium’s HSA6, materials whose performance exceeds AA6611, the tensile strength can reach Above 400 MPa, the weight reduction effect and strength are better.

Welding technology of battery case

The difficulty of the battery case lies in the welding process of the profiles. Experts pointed out that the welding process of the battery case is difficult because the thickness and section of the profiles are different. There are many combinations of thicknesses in each place, including thin and thick plates, thin plates and thin plates, bottom plates and beams, and water-cooled plates and beams. There are huge thickness differences, so it is very difficult to control heat input in welding.

Secondly, the battery case product is large, the welding bead is many, the welding bead is long, and the welding bead is required to be small. In response to these problems, Minth has developed welding specification synchronous swing technology, SAWP low heat input technology, P-Stitch fish scale welding technology, P-MIX welding technology, thick plate high-speed welding spatter-free technology, AC AC pulse method, 1.6mm high-efficiency welding wire,  Welding application and other seven methods.

The change of the battery pack will also bring about the process change of the battery case. At present, the layout of battery packs is developing in the direction of reducing structural parts and increasing the amount of charge. There are three routes for battery packs, namely current battery module, no module (CTP), and CTC battery integration solution. CTP is a module-free solution that reduces or removes the three-level pack structure of the battery “cell-module-whole package”.

By now, there are two different technical routes: the plan of completely canceling the module represented by byd blade battery. The plan of combining small modules into large modules, represented by the CTP technology of CATL. CTC directly integrates the battery cells inside the floor frame, and uses the upper and lower panels of the floor as the battery shell, which is a further integration of the CTP scheme. , which fundamentally changes the way the battery is installed.

The fusion design of the water cooling system and the battery tray is also a solution currently under development, which replaces the design of the external cooling system and can improve the heat dissipation efficiency of the battery. The specific method is to connect the heat dissipation system and the bottom plate to form an integral bottom plate, and then connect it to the frame by friction stir welding.

China’s battery case development technology is advanced

The battery case is an emerging track for electric vehicles, and Chinese companies are expected to grow into the world’s leading suppliers. There are many new entrants from Chinese companies making battery case. At present, from the perspective of Chinese enterprises, Lingyun, Minth Group, and Hesheng are in the first echelon of the industry.

Lingyun masters the core technology of aluminum alloy battery case, and has obtained battery case orders from Porsche, BMW, Mercedes-Benz, Great Wall Motor, GAC New Energy, BAIC New Energy and other car companies. Its light welding technology is also ahead of other factories.

Vadashav has cutting-edge lightweight technology and aluminum and steel integrated manufacturing processes, and has been recognized by well-known manufacturers such as Volkswagen and BMW. Vadashav’s main products are automotive metal parts, including doors, tailgates, hood components and structural parts, etc., and it is relatively advanced in the field of automotive lightweight aluminum alloy manufacturing.

The company’s processing technology in aluminum alloy lightweight auto parts products has been rapidly improved, and it has obtained domestic supporting qualifications for high-end models such as BMW and Mercedes-Benz.

Minth Group has made rapid progress in battery case. In 2020, it set up two factories in Serbia to start the layout of battery case and aluminum parts production lines. At present, the construction of many factories has been completed and the installation and commissioning of many large extrusion lines have been carried out.

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