Helium Accumulation Chamber Leak Test Equipment 1.0E-6 Mbar.L/S For EV Battery Pack Hood Method Detection

A finished battery pack cannot be evacuated, cannot be wetted, and cannot be inspected seam by seam within a takt. The hood method is the only one of the three that keeps the pack dry, gives you a number, and fits a production shift — which is why this is the system we build for pack-level sealing verification.

Every leak testing method assumes something about the part. Vacuum chamber testing assumes the part can be evacuated, and a pack cannot — the cells, the structural foam, and the seals are not designed for external vacuum, and pulling one down will damage it or, worse, deform it in a way that creates the leak you were testing for.

Water immersion assumes you can dry the part afterwards. On a high-voltage assembly, that assumption is unacceptable, and it leaves no record you can show a customer.

Air decay assumes a small, stiff, temperature-stable volume. A pack is the opposite: tens of litres, a lot of thermal mass, and an acceptance criterion that is usually far below what air can resolve in a shift, let alone a takt.

The hood method sidesteps all three. The pack stays at ambient pressure, stays dry, and the measurement is a tracer gas concentration rather than a pressure difference — so the material and the volume stop fighting the test.

The pack goes into a sealed hood of known volume and is charged with a helium mixture through its service port. Anything that escapes accumulates in the hood. A circulation fan mixes the hood atmosphere so there are no dead zones, and a mass spectrometer samples that atmosphere and measures the rise over a fixed window.

The key point, and the one that decides your cycle time: sensitivity is governed by accumulation time, not by the analyser alone. Doubling the dwell roughly doubles the signal. There is always a trade between the two, and it should be your trade — we will tell you the shortest dwell that honestly meets your criterion instead of quoting a sensitivity number in isolation.

Two practical details make the difference between a stable result and an argument. First, the hood atmosphere is monitored between cycles: a workshop where a cylinder has been venting will otherwise drift the readings all morning. Second, the hood and the pack are both recovered, because on a large volume the pack itself holds most of the gas.

A hood that is much larger than the pack dilutes the signal and buys you nothing. We size the hood to the pack envelope with enough clearance for loading, not to a round number.

Helium is light and will stratify. Without a fan and a baffle arrangement, the sample point reads whatever is local to it. Our hoods circulate and were checked for dead zones during commissioning, not assumed.

Ambient helium compensation is not a nice-to-have on a pack line; it is the difference between a usable limit and a permanent argument with your quality team.

Both are evacuated back through the recovery loop after the measurement. Without that, a large-volume pack vents its whole charge every cycle and the running cost quietly becomes the biggest number in the business case.

Pack volume, charge pressure, and dwell all change with the product. Recipes are selected by barcode so nobody edits parameters at the station.

1. Load and seal — pack into the hood, lid closed and sealed, barcode scanned, service port connected.
2. Background check — the hood atmosphere is sampled before charging; if ambient helium is too high, the cycle waits rather than producing a false fail.
3. Charge the pack — helium mixture to the agreed pressure through the service port.
4. Accumulate — fan circulation for the recipe dwell; the analyser logs the concentration rise.
5. Measure and convert — the rise is integrated and converted to a leak rate in mbar·L/s, then compared with the limit.
6. Recover and release — hood and pack recovered, lid opened, pack released with a verdict and a stored record.

Pack customers usually arrive with an IP67 or IP6K9K requirement and no leak rate, and expect a conversion table. There is no universal one, because it depends on pack volume and on the pressure profile the standard applies. What works is an empirical correlation on your own packs:

• Test known-good packs and record the spread. That establishes what normal looks like on your line.
• Introduce a calibrated leak at a known location and confirm the hood sees it at the dwell you plan to run.
• Set the limit with margin — typically one third of the specified rate — so a marginal pack is caught before the vehicle plant does.
• Revalidate after a design change. A new pack volume changes the conversion; do not inherit the old limit.

Hood testing measures the whole pack, so it tells you that something leaks, not which seam. Keep a portable sniffer at the rework bench: a two-minute sweep on the suspect area usually identifies the joint, and that is far cheaper than scrapping or reworking blind.

If the pack design allows evacuation, a vacuum chamber is faster and more sensitive and you should buy one. It is the sealed pack with a large internal volume that makes the hood the practical answer — and that describes almost every finished pack we have been asked about.

A finished battery pack is the least cooperative object in leak testing: too large to evacuate, too valuable to wet, and too tightly specified for air decay. That constraint is what shaped the machine we build.

HongCe has been making test equipment in Guangzhou since 2012 — 100 to 200 people, about half of production exported, customers that include third-party laboratories and certification bodies. Our three families are IEC and EN safety apparatus, IP ingress equipment and environmental chambers, and leak detection spanning helium chambers, sniffer units, hoods, and recovery.

Hood work is where those disciplines meet: gas handling, an enclosure that opens a hundred times a shift, background monitoring that keeps a workshop's stray helium out of the verdict, and a recovery loop sized for the whole pack rather than for the hood alone.

Every system is leak-checked against a calibrated standard and recorded under its serial number before shipment, commissioned on site with correlation runs on your own packs, and supported from Guangzhou with spares dispatched within 48 hours.

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