Sitting under the floor of an EV, the battery tray (battery enclosure) carries hundreds of kilograms of cells and protects them from crash loads, vibration, water, and heat. It often contributes to body stiffness as well — making it a sourcing item that directly drives both safety and cost.
How a battery tray is built
A typical tray consists of (1) a perimeter frame and floor, (2) internal reinforcement beams (cross members), (3) cooling plates, (4) sealing and waterproofing, and (5) mounting brackets. What looks like one "box" is really an assembly of extrusions, roll-formed sections, stampings, and castings, joined by welding and bonding.
- Frame & reinforcement beams — typically aluminum extrusions or roll-formed high-strength steel
- Cooling plates — brazed/joined high-conductivity aluminum (e.g. 3003 series)
- Floor & covers — aluminum sheet or stamped steel
- Joining — a mix of laser welding, MIG, FSW, and structural adhesives
Aluminum or high-strength steel?
Frame and beam materials split broadly into aluminum extrusion and high-strength steel. Aluminum is light and corrosion-resistant but costs more as a material. In recent years, roll forming ultra-high-strength steel (590–1700MPa) and laser-welding it into closed sections has been gaining adoption as a way to balance cost with crash performance.
- Aluminum extrusion — light, corrosion-resistant, thermally conductive; easy to integrate cooling
- Roll-formed high-strength steel — lower material cost, high strength; ideal for long, constant-section beams
- Hybrid — aluminum perimeter with high-strength-steel internal beams is also common
What to check when sourcing
- IATF 16949 (automotive quality management) certification
- Mill certificates and how grades map across standards
- Laser-weld quality control (macro sections, leak testing, etc.)
- Dimensional accuracy of long parts, plus shipping and packaging plans
- Who pays for and owns the dies / roll tooling
- How prototype-lot terms differ from volume-production terms
In Japan–China sourcing specifically, grade naming (e.g. how European-style designations like HC340/590DP map to Chinese GB standards) and inspection-report formats are where misunderstandings happen most. Fixing "which standard, which format" before ordering prevents most incoming-inspection disputes.
What the FENTEX network can do
The FENTEX partner network includes an IATF 16949-certified specialist in 590–1700MPa roll forming + laser welding that mass-produces battery-tray parts for major EV makers, and a full-cycle aluminum plant (cast rod through extrusion, machining, and finishing) with a battery cooling-plate track record. Send one drawing for a free quote — one point of contact from prototype to production, in Japanese, Chinese, or English.