Analysis of Aluminum Alloy Battery Pack Housing Structures and Joining Technologies for New Energy Vehicles

As power battery systems for new energy vehicles evolve toward higher energy density, lightweighting, and greater integration, the battery pack housing has transitioned from a simple structural shield into a critical component that simultaneously handles load-bearing, sealing, thermal management, and system integration. For power batteries, while cell material systems and battery management technologies continue to improve, reducing housing weight to boost system-level energy density represents a direct and effective engineering approach.

 

Aluminum alloys offer low density, high specific strength, excellent corrosion resistance, good thermal conductivity, favorable formability, and recyclability, making them highly valuable for new energy vehicle battery pack structures. Compared to traditional steel housings, aluminum alloy structures reduce weight while meeting load-bearing requirements, providing greater design flexibility for battery module layout, cooling system integration, and vehicle range optimization.

 

Common structural designs for new energy vehicle battery systems include extruded aluminum housings, stamped aluminum sheet structures, and hybrid structures combining profiles and sheets. Extruded profiles, in particular, offer highly customizable cross-sections; features such as multi-chamber designs, reinforcing ribs, and localized solid sections allow for increased structural rigidity while optimizing material usage. For prismatic cell systems, the housing design must also be coordinated with the cell arrangement, cooling channels, and the sealing structure of the top cover.

 

At the cell level, the aluminum can serves to encapsulate the cell interior and provide external protection, whereas the battery pack housing is primarily responsible for the structural load-bearing and environmental protection of the entire battery system; the two differ significantly in dimensions, material thickness, forming methods, and connection requirements. Consequently, the mechanical, electrical, and thermal management requirements for both the cell casing and the battery pack housing must be evaluated separately during the structural design process.

 

 

 

A typical aluminum alloy battery pack housing consists of a frame, a base plate, a top cover, and internal mounting structures. The frame and base plate bear the primary loads from the battery modules and associated components, while the top cover primarily provides protection and sealing, in addition to contributing to overall structural rigidity. Depending on the specific vehicle model and battery system layout, components such as cooling channels, mounting brackets, structural reinforcements, wiring harness mounts, and high-voltage connection zones may also be integrated.

 

For aluminum battery enclosures in new energy vehicles, structural design cannot focus solely on weight reduction; it must simultaneously meet requirements for strength, stiffness, fatigue life, crash safety, sealing, and manufacturability. Connection zones within the housing are often critical areas for structural design and reliability validation, particularly given the operating conditions involving long-term vibration, thermal cycling, and road impacts.

 

The frame and base plate typically utilize extruded aluminum alloy profiles featuring multiple internal cavities. Optimizing the profile cross-section allows for a high area moment of inertia with relatively limited material usage. Reinforcing ribs or localized solid sections can be incorporated in areas subject to high loads, while unnecessary material can be removed from non-critical load-bearing areas by reducing wall thickness, optimizing cavity dimensions, or employing post-extrusion machining.

 

In addition to supporting the weight of battery cells and modules, the battery pack base plate may need to integrate water or liquid cooling channels. Consequently, its cross-sectional design must balance load-bearing capacity, space for cooling channels, manufacturing feasibility, and sealing requirements. For battery packs utilizing liquid cooling, the continuity of internal channels and the sealing quality of welded areas are of particular importance.

 

 

Extruded 6000-series aluminum alloys-such as 6061-T6, 6005A-T6, and 6063-T6-are commonly used for traction battery enclosures. Different alloys vary in terms of strength, extrudability, cross-sectional complexity, and material cost; therefore, material selection must be determined by considering both structural loading requirements and manufacturing processes.

 

6061-T6 offers excellent overall mechanical properties, making it suitable for frames and load-bearing components that require high strength and structural stability. 6005A-T6 balances strength with extrusion formability, making it appropriate for larger profile structures.

 

6063-T6 offers superior formability, making it better suited for complex cross-sections or structural areas with lower load-bearing requirements. During the design process, a thicker profile wall is not necessarily better. Excessive wall thickness increases material usage and structural weight, while also raising costs associated with extrusion, welding, and downstream processing. Therefore, wall thickness and the placement of reinforcing ribs should be determined based on actual load paths, ensuring material is distributed where it can most effectively bear loads.

 

For structures requiring secondary processing, aluminum stamped parts can be utilized for components such as localized brackets, mounting tabs, protective shields, and connecting aids within the housing. Compared to simply increasing the thickness of the main profile, localized reinforcement using separate stiffeners can sometimes achieve a superior balance between weight and structural performance.

 

 

 

Aluminum alloy battery pack housings can be designed as integral extruded structures or as assemblies formed by welding multiple profiles together. Integral profiles offer superior structural continuity and reduce the number of connection interfaces; however, they may entail larger profile dimensions, more demanding tooling requirements, and increased downstream machining.

 

Welded assemblies, conversely, reduce the manufacturing complexity associated with large, intricate profiles and offer greater design flexibility. By combining profiles with different cross-sections, the structural configuration can be tailored to specific battery pack dimensions and load requirements, while also potentially lowering tooling and processing costs.

 

For specific mounting areas, localized mounting features can be created through aluminum stamping or machining. The specific approach should be selected based on part dimensions, material thickness, production volume, and precision requirements. For high-volume production projects, a comprehensive evaluation of the combination of stamping, extrusion, and machining processes is typically required during the early stages of product development.

 

 

 

Primary joining methods for aluminum alloy battery pack housings include friction stir welding (FSW), MIG welding, riveting, press-fitting (self-piercing riveting/clinch-riveting), and adhesive bonding. Friction stir welding is a notable solid-state joining technique; unlike traditional fusion welding, the material does not undergo a complete melting process during the weld.

 

For long-distance structural joints-such as those connecting the battery pack baseplate to the frame-friction stir welding offers advantages including minimal welding deformation, stable joint microstructure, and suitability for continuous welding operations. Since the weld pool solidification process characteristic of traditional fusion welding is absent, the risk of defects such as porosity, inclusions, and hot cracking is reduced.

 

In practical structural design, the cross-sectional shape of the weld zone must align with the movement envelope of the friction stir welding tool. Internal stiffeners, fillets, and localized solid sections within the profiles must provide adequate support for the welding process. If the weld depth is significant, the structural rigidity of the corresponding area must be increased accordingly; otherwise, localized deformation may occur under welding pressure.

 

For the connection between base plates, either butt-joint or lap-joint configurations may be selected based on the structural design. Double-sided welding enhances the structural stability of the joint area but increases the processing path and manufacturing time; therefore, the choice depends on the product structure and production cycle requirements.

 

 

The connection between the frame and the base plate is a critical load-bearing interface for the battery pack housing, and the joining method directly impacts overall structural strength and sealing performance. Common approaches include double-sided friction stir welding (FSW), or a combination of external FSW with internal MIG welding and sealing treatments.

 

Double-sided FSW yields a continuous joint interface and helps minimize welding-induced deformation. However, the structural design must accommodate sufficient clearance for the welding tool, which may necessitate specific cross-sectional dimensions for the frame.

 

Another approach involves using FSW on the exterior and MIG welding on the interior. This configuration offers relatively high manufacturing efficiency and greater flexibility in profile design; however, weld quality and sealing performance in the internal fusion-welded zones require careful attention. If potential leakage paths exist, secondary protection using sealant may be necessary.

 

For certain complex connection zones, stamped aluminum sheet metal components can be used as independent connectors, subsequently joined to the main housing via riveting, welding, or bolting. This strategy reduces the manufacturing complexity associated with producing intricate structures as single, integrated units.

 

 

Battery packs for new energy vehicles are typically mounted at the vehicle's underbody or near the chassis, exposing them to environmental factors such as rain, mud, standing water, temperature fluctuations, and mechanical vibration over the long term. The sealing design of the housing is critical not only for the longevity of structural components but also for the electrical safety of the battery system.

 

During the design process, it is crucial to control potential leakage paths, such as baseplate welds, frame joints, top cover flanges, fastener mounting holes, and interfaces for wiring harnesses and high-voltage connections. For housings utilizing welded connections, weld quality control and seal testing must be employed to ensure there is no significant risk of leakage in the joint areas.

 

Sealing strips, foamed sealing materials, or other elastic sealing structures are typically used between the housing and the top cover. Sealing design must also address fastener areas to prevent bolt holes or rivet holes from becoming pathways for moisture to enter the housing.

 

In some configurations, electrical components-such as insulated busbars-are located in proximity to the battery pack's internal structures; therefore, factors such as insulation clearance, mounting methods, and the impact of the sealed environment on the long-term operation of electrical components must be considered.

 

 

Aluminum alloy battery packs do not rely solely on extrusion processes. Components such as mounting brackets, connecting plates, reinforcements, and localized structural parts can be mass-produced using aluminum metal stamping. Stamping offers advantages such as rapid production cycles, high material utilization, and suitability for mass production.

 

For parts with complex geometries and high dimensional accuracy requirements, a combination of aluminum sheet metal stamping and CNC machining may be employed. Stamping is used to form the basic profile and primary structure, while machining performs precision finishing on holes, mounting surfaces, and critical dimensions.

 

During the project development phase or for small-batch production, custom aluminum stamping can reduce investment in specialized tooling and facilitate rapid structural adjustments based on prototype test results. Upon transitioning to mass production, tooling, material utilization, and production cycles must be further optimized to control unit manufacturing costs.

 

For localized brackets, mounts, and auxiliary structures for electrical connections, stamped aluminum parts complement extruded profiles and welded structures, offering greater flexibility in the overall battery pack manufacturing strategy.

 

 

The density of aluminum is approximately one-third that of steel; consequently, replacing certain steel structures with aluminum alloys offers significant potential for weight reduction. However, the actual weight reduction achieved is not simply a function of material density differences; it also depends on cross-sectional geometry, wall thickness, joining methods, and reinforcement structures.

 

The core of lightweight design lies in optimizing load paths. For areas subjected to significant bending and impact loads, stiffness can be enhanced by increasing cross-sectional height, incorporating reinforcing ribs, or utilizing multi-chambered structures, rather than simply increasing the thickness of the entire panel.

 

For non-primary load-bearing areas, material usage can be reduced through localized thinning, the inclusion of cutouts, and structural optimization. CAE (Computer-Aided Engineering) finite element analysis allows for the assessment of stress and deformation in the housing under conditions such as acceleration, vibration, crushing, and other typical operating scenarios, enabling the identification of potential weak points during the design phase.

 

It is important to note that lightweighting the battery pack must not come at the expense of safety. Structural design requires striking a reasonable balance among weight, stiffness, strength, fatigue life, crash safety, manufacturing costs, and sealing performance.

 

 

During the development of the battery pack structure, CAE simulation is used to validate various material and cross-sectional design options. Typical analyses include static strength, modal analysis, vibration, crushing, impact, and local stress analysis at connection points.

 

For instance, regarding structures utilizing 6005A-T6 alloy, calculated maximum stress values ​​can be compared against the material's yield strength, while also accounting for safety factors, weld joint performance, and long-term fatigue loading.

 

Crush scenarios require particular attention to the safety clearance between the battery modules and the housing. Significant structural deformation that intrudes into the cell area could increase the risk of mechanical damage to the cells. Therefore, simulation results must be evaluated in conjunction with actual battery module dimensions, safety clearances, and the vehicle's overall structure.

 

In addition to CAE analysis, the prototyping stage should involve validation testing for airtightness, water resistance, vibration, mechanical strength, and environmental durability. While simulation serves to shorten design iteration cycles, physical testing is essential to verify product performance under real-world operating conditions.

 

 

 

As new energy vehicle platforms evolve toward high voltage, high capacity, and high integration, the functionality of battery pack housings continues to expand. Future structural designs will place greater emphasis on the synergy between the housing, cooling system, electrical connections, and thermal management.

 

On one hand, aluminum alloy profiles retain a significant advantage in lightweighting; multi-chamber extruded structures, localized reinforcement, and integrated cooling channels will remain key design directions. On the other hand, the combined application of stamped aluminum sheets, cast aluminum structures, and extruded profiles will increase to meet the manufacturing requirements of diverse vehicle models and battery platforms.

 

Regarding cell packaging, aluminum shells for lithium-ion batteries must balance forming precision, corrosion resistance, sealing integrity, and the requirements of the internal electrochemical environment. At the battery pack level, the focus shifts to structural strength, sealing and protection, thermal management, and crash safety.

 

For prismatic battery systems, the design of the aluminum casing and the pack structure must fully account for cell arrangement, tolerance accumulation, and module mounting methods to minimize structural interference during assembly.

 

Deep drawing processes are suitable for certain battery metal housings with complex spatial geometries; key design considerations include material elongation, sheet thickness control, corner radii, and the risk of cracking during forming.

 

For aluminum pack housings, future design trends will prioritize integration-enabling structural components to perform multiple functions (such as cooling, load-bearing, mounting, and protection) to reduce the total number of discrete parts.

 

Overall, there is no single, fixed technical pathway for aluminum alloy battery pack housings. Manufacturing processes-such as extrusion, stamping, machining, friction stir welding, MIG welding, riveting, and adhesive bonding-must be combined based on product dimensions, material systems, production volume, precision, and performance requirements. Process routes adopted by aluminum stamping companies may vary significantly depending on production volume and structural complexity; therefore, the solution determined during the product development phase should prioritize structural requirements and manufacturing feasibility.

 

From an engineering perspective, lightweighting the battery pack housing is not merely a matter of substituting aluminum for steel; rather, it is a systems engineering endeavor involving the interplay of materials, cross-sectional structures, joining processes, sealing designs, simulation validation, and mass production. Only by considering structural performance and manufacturing processes concurrently can one reduce weight while maintaining the strength, sealing integrity, and long-term reliability required of the battery system.

 

For new energy vehicle battery pack housings, engineering teams involved in product development or volume procurement should further confirm specific technical solutions with manufacturers possessing the requisite capabilities in aluminum alloy stamping, extrusion, and welding, taking into account material grades, structural dimensions, forming processes, welding methods, sealing ratings, and inspection requirements.