Aluminum Welding for EV Battery Trays

Common base metals and welds

The battery tray is the structural part carrying the battery modules — usually a frame built from extrusions, then welded to the base plate, cross-members and mounting brackets. It is both a load-bearing structure and a sealed enclosure: the seams must be leak-tight to achieve the water- and dust-protection rating and to prevent coolant leakage. The base-metal and service combinations most commonly seen on the floor are as follows:

• 6xxx-series extrusions (e.g. 6061, 6082): widely used for the tray frame, cross-members and floor profiles — adequate strength, heat-treatable, and the most common base metal for the tray frame, where the welds are mostly long straight seams and sealing seams.
• 5xxx-series plate (e.g. 5083, 5754): used on more heavily loaded areas or base-plate panels, with good strength retention after welding, often forming mixed joints with 6xxx extrusions.
• Sealing and density requirement: tray seams must be leak-tight, dense and low in porosity — pores or lack of fusion create leak paths that directly compromise the battery's water-, dust- and leak-protection, the core quality concern in tray welding.
• High volume and distortion control: trays are mostly high-volume repeat welding of similar joints, demanding a steady cycle; meanwhile the seams are concentrated and thermal distortion accumulates readily, so distortion must be controlled to maintain enclosure flatness and downstream assembly dimensions.

Practical welding notes

• Ensure sealing and weld density: sealing seams should be continuous, free of arc breaks and lack of fusion, with crater fill at the stop to avoid leak paths. The air-tightness and density of the seam directly determine the battery's water-, dust- and leak-protection — the core requirement in tray welding.
• Stable feeding for a continuous cycle: trays are mostly high-volume repeat welding, where feeding stability directly affects the continuous-welding cycle. TGM wire has a clean surface and uniform diameter, giving low feed resistance and a stable arc, reducing feed stoppages and helping high-volume continuous welding run steadily.
• Control distortion for assembly fit: tray seams are concentrated and thermal distortion accumulates readily. Plan the welding sequence sensibly, apply symmetrical and back-step welding, control heat input and interpass temperature, and use rigid fixturing to maintain enclosure flatness and assembly dimensions.
• Clean before welding, shield well: before welding, thoroughly remove the oxide film, oil and moisture, and shield with pure argon or an argon-helium mixture to reduce porosity and improve weld density — the fewer the pores, the more reliable the sealing seam, so this step must be carried out rigorously.

Further reading: for the troubleshooting sequence when porosity appears, pre-weld cleaning practice and shielding-gas checks, see the guide to aluminum weld porosity.