EV Battery Enclosure Casting RFQ Checklist

# EV Battery Enclosure Casting RFQ Checklist: Pack Housing Requirements Buyers Should Define

EV battery pack housing aluminum casting is difficult to quote because the buyer may need sealing rails, flatness zones, thermal interfaces, coating or weldability assumptions, machining datums, and validation records in the same RFQ. Treat this article as a buyer-side checklist: it does not assume a fixed leak-test result, crash result, weld approval, process route, or validation package before the drawing and program requirements are reviewed.

If you are still at the alloy-shortlisting stage, the A356 vs ADC12 alloy selection guide covers the underlying trade-offs in casting process, mechanical properties, and cost. For a sourcing package, use the EV battery enclosure OEM quote route or the aluminum casting RFQ checklist so suppliers can separate drawing facts from assumptions.

Start with the RFQ data buyers should send

For a drawing-ready battery enclosure, send these inputs before asking for unit price:

• •Part scope: rail, frame, cover, tray, housing, cooling-plate interface, or hybrid assembly.
• •Drawing package: 2D PDF, STEP, revision, GD&T, datum scheme, and critical sealing or flatness zones.
• •Functional assumptions: leak-test method and acceptance criteria if required, coating or masking scope, weldability or fastening requirements, thermal interface, and environmental exposure.
• •Process preference: low-pressure casting, gravity casting, die casting, or supplier recommendation with DFM notes.
• •Inspection package: CMM, flatness map, material certificate, coating record, leak-test assumption, FAI, PPAP-style records, traceability, or customer-specific forms if required.
• •Commercial context: annual volume, prototype quantity, tooling status, destination, Incoterm, packaging, and launch timing.

Submit an EV battery enclosure RFQ

Why Battery Pack Housings Drive Unusual Casting Requirements

A battery pack housing is not simply a large tray. It performs at least five functions in a single part:

• •Structural carrier for cell modules — must hold module weight (often 300-600 kg for passenger EVs) through road-load fatigue cycles without distortion or resonance.
• •Crash load path — in a side-pole or side-barrier impact, the housing participates in energy absorption and must prevent intrusion into the cell stack.
• •Environmental barrier — typically IP67 or IP6K9K sealing, protecting cells from water, dust, and salt spray.
• •Thermal interface — houses or interfaces with the cooling plate, so the wall thickness and surface flatness affect thermal contact and therefore cell temperature uniformity.
• •Weld and bolt partner — joins to stamped lids, extruded frames, cooling plates, and vehicle floor structures via MIG, friction stir welding (FSW), or mechanical fasteners.

Each function pulls the design in a different direction, and the casting supplier ends up negotiating the trade-offs.

Alloy Selection: Why AlSi7Mg (A356/A357) Wins Most Battery Programs

The dominant alloy family for gravity and low-pressure cast battery housings is AlSi7Mg, covering A356, A356.2, A357, and their regional equivalents. Three reasons:

• •Weldability. Unlike high-iron secondary alloys (ADC12/A380), primary AlSi7Mg welds reliably with ER4043 or ER4047 filler. Battery housings almost always need welded lids or cooling plate joints.
• •T6 mechanical properties. After solution and aging, A356-T6 reaches ~240 MPa UTS and ~170 MPa YS with 6-8% elongation. That elongation matters for crash load cases where the housing must deform without fracturing.
• •Low hydrogen susceptibility in controlled foundries. With rotary degassing to below 0.15 ml/100g, porosity can be kept low enough for leak test acceptance without requiring impregnation.

ADC12 and A380 high-pressure die castings are sometimes used for smaller pack housings where cost dominates and the lid/frame joint is bolted rather than welded. For gigacasting-scale integrated structural castings, alloys like Castasil-37 and AlSi10MnMg (Silafont-36 family) are more common because they are heat-treatment-free and designed for vacuum-assisted HPDC. Bohua reviews battery enclosure RFQs by comparing AlSi7Mg/A356-family, ADC12/A380-family, gravity casting, low-pressure casting, die casting, and machining scope against the drawing instead of assuming one default process route.

Leak Tightness and Porosity Limits

Battery housings are leak-tested, and the acceptance criterion is tight. A typical spec looks like:

• •Air decay or helium leak test at 30-50 kPa, leak rate < 5 x 10^-3 mbar·L/s (helium) or equivalent in air decay.
• •100% part inspection, not sample-based.
• •After final machining, because critical sealing surfaces are machined and porosity revealed by cutting can open a leak path.

Translating this to foundry control:

• •Degassing verified on every shift by reduced pressure test (RPT) or AlScan.
• •Shrinkage porosity controlled by gating and riser design plus simulation (MAGMAsoft, FLOW-3D) — not by post-casting impregnation as a safety net.
• •Critical sealing-surface regions designed with extra local thickness or directional solidification so last-to-freeze zones land outside the seal.
• •100% X-ray or CT on the first dozen parts of a new program to verify internal quality before leak testing.

If a supplier routinely relies on vacuum impregnation to pass leak test, that should be clarified before sourcing award. Impregnation may be acceptable as a contingency on mature parts, but the RFQ should define whether the buyer expects leak-test acceptance without impregnation, when impregnation is allowed, and how that decision is recorded.

Dimensional Control on a Large Footprint

Passenger-car battery housings commonly span 1,500-2,000 mm in length. A general casting tolerance class like ISO 8062 DCTG 8-10 applied over that length produces absolute tolerances of ±2-4 mm on cast dimensions, which is too loose for module location and cooling-plate interface. Real programs handle this with:

• •Cast-then-machine approach on all critical sealing and mating surfaces. Casting tolerances apply only to non-functional surfaces.
• •Fixture datum strategy defined early — the CMM and machining fixtures use the same 3-2-1 datum scheme to avoid cumulative drift. Our CMM inspection requirements for cast aluminum parts post covers datum strategy in detail.
• •Stress-relief heat treatment after rough machining for large thin-wall housings to control residual stress distortion before finish machining.
• •Fixture gauges rather than free-state CMM for high-volume check of module-bay flatness and cooling-plate seat profile.

Crash Load Cases and Why Elongation Matters

US FMVSS 305 and UN ECE R100 do not prescribe a specific material property target, but OEM internal standards translate side-pole and side-barrier intrusion requirements into housing-specific load cases. A typical target is to keep cell intrusion under 20 mm at a specified barrier velocity. The housing must deform plastically without fracture at the impact zone and without tearing at welded joints.

That drives two casting requirements:

• •Minimum elongation of 5-7% at the cast-and-T6 condition — not average but 3-sigma lower bound. Hydrogen porosity depresses elongation, so degassing discipline is a structural requirement.
• •Weld-line control in simulation and gating so that last-to-fill fronts do not land in the crash load path. Cold-shut-prone regions should be designed out, not inspected out.

Suppliers should be willing to share tensile test data by location (coupon cut from representative crash zones), not just separately-cast test bars, because separately-cast bars overstate the elongation available in the actual part wall.

Weldability and Joint Design

Most pack housings are not a single casting — they are a cast tray welded to a stamped or extruded frame, or bolted to a cast lid. The casting-side requirements:

• •Hydrogen content below 0.15 ml/100g at pour. Higher hydrogen shows up as weld-bead porosity during fusion welding.
• •Iron content controlled. AlSi7Mg targets Fe < 0.15% for primary-grade material. Higher Fe in secondary alloy reduces weld integrity and ductility.
• •Weld prep surfaces machined to remove the cast skin and any embedded oxide. Weld directly on a cast surface is possible but yields inconsistent results.
• •FSW compatibility if the OEM uses friction stir welding for the cooling plate joint. FSW on cast AlSi7Mg is well-characterized — see the ASM Handbook Vol 6A: Welding Fundamentals and Processes for published joint properties and parameter windows.

Inspection Protocol That OEMs Actually Require

A representative control plan for a production battery housing:

This is heavier inspection than a non-safety-critical casting and should be priced in from the start. A supplier quoting a battery housing at the same inspection cost as a generic pump body is either under-scoping the program or planning to cut corners.

What to Verify Before Awarding the Business

Before signing a purchase order for a battery housing program, a buyer should confirm:

• •Prior experience with a structural, leak-tight casting of similar size and wall thickness — not just "aluminum casting experience" in general.
• •Casting simulation capability in-house (MAGMAsoft, FLOW-3D, or ProCAST) and a willingness to share simulation output during DFM review.
• •Rotary degassing with documented per-shift RPT and hydrogen targets.
• •IATF 16949 certification with the scope explicitly covering casting, not only machining.
• •A detailed inspection plan aligned with the OEM control plan, including X-ray and leak-test capacity to handle program volume.
• •Tensile data from part-cut coupons, not only separately-cast bars.

Battery enclosure RFQs reward suppliers who separate drawing facts, validation assumptions, inspection cost, and tooling risk before quoting. The buyer should be able to see which leak-test, flatness, coating, machining, and documentation assumptions are included in the quote.

For a quote path that carries this context into the inquiry form, use the EV battery enclosure OEM quote guide or submit the drawing package directly.