Why Leak Testing Is Critical for EV Thermal Management
Electric vehicle battery packs operate at cell temperatures that must be maintained within ±2–5°C for optimal cycle life. Liquid cooling circuits — aluminum extrusions, heat sinks, and flexible cooling tubes — carry coolant (typically 50% ethylene glycol / water) at pressures of 150–400 kPa. A leak of even 1 mL/min will result in coolant loss, thermal runaway risk, and battery warranty claims.
As EV energy densities increase, cooling circuit geometries become more constrained, with thinner walls and more complex bent tube profiles. This makes fixture design and test method selection more critical.
Common EV Components Requiring Leak Testing
- Battery tray / cooling plate: Large aluminum die-cast assemblies. Test pressure: 300–500 kPa. Method: direct pressure decay.
- Liquid cooling tubes: Bent aluminum or rubber extrusions. Test pressure: 298–350 kPa. Leak threshold: ±1.0 kPa. Method: direct pressure decay. Cycle time: 23 s (Charge 6 s / Stabilize 8 s / Measure 8 s / Exhaust 1 s).
- Water-cooled heat sink: Multi-port aluminum heat exchanger. Test pressure: 300 kPa. Method: direct pressure decay.
- EV sensors and motor housings: IP-rated enclosures. Test pressure: 50–150 kPa. Method: direct pressure decay or volume method.
Test Method for Liquid Cooling Tubes
Aluminum cooling tubes present a specific challenge: their bent geometry means conventional axial-clamp fixtures apply force to tube ends, deforming thin walls and generating false rejects. The correct approach uses inner-expansion connectors (such as the Figurtech LT-G01 bend-clamp) that seal from inside the tube bore — applying zero axial or lateral force to the tube wall.
The Figurtech LY Series direct pressure tester executes the following test cycle for a standard 6–52 mm OD liquid cooling tube:
| Phase | Duration | Action |
|---|---|---|
| Charge | 6 s | Pressurize to 325 kPa nominal |
| Stabilize | 8 s | Equalize and allow thermal settling |
| Measure | 8 s | Record pressure decay |
| Exhaust | 1 s | Release and prepare for next part |
| Total | 23 s | Accept window: 298–350 kPa, ±1.0 kPa decay |
Thermal Drift Compensation
At high test pressures (300+ kPa), shop-floor temperature fluctuations of even 1°C can produce 1 kPa of apparent pressure change. Without compensation, this produces chronic false rejects during shift transitions or near HVAC ducts. Figurtech LY Series instruments include on-board thermal drift compensation that measures and subtracts temperature-induced pressure variance, maintaining the ±1.0 kPa acceptance window across full production shifts.
Large Battery Tray Testing
Battery trays are large-volume assemblies (typically 5–50 L internal volume) tested at 400–500 kPa. For these components, direct pressure decay is the correct method — the large volume provides inherent thermal stability, and the high test pressure provides adequate signal-to-noise ratio for the leak threshold. Connectors must be rated above the test pressure; the Figurtech LT-KZ02 stainless-steel claw connector is rated to 50 bar (5000 kPa) — 10× the typical battery tray test pressure.
Figurtech supplies complete leak test systems for EV thermal management components, including instruments, fixtures, and standard leak calibration artifacts. Contact us to discuss your cooling circuit geometry and test specification.