pressure relief valves for EV batteries, gears and motors

Every headline figure in this market traces back to the supplier's own bench. Gore's moisture result — under 20 mg per day at 22 °C and 50 percent relative humidity, described as less than one-tenth that of many commercially available dual vents — is attributed to Gore laboratory testing, and its durability claim to Gore testing after standard automotive aging. Freudenberg's 190 L/s at 300 mbar is a factor-of-2.5 gain measured against its own previous generation. Donaldson publishes a 115 mbar opening pressure, roughly 100 L/s at 100 mbar, IP67/68/69K and an operating range of −40 to 125 °C on a product datasheet. These are design and in-house test figures, and I found no independent measurement of a commercial pack vent's flow performance in the public record — which leaves the sizing question answered by supplier numbers alone.

The relief valve is being claimed by the organisations that write the specification. Cell and vehicle makers are filing their own pack-side designs — LG Energy Solution, Samsung SDI, CALB, Toyota, Ford, Maserati and SAIC Volkswagen among them — and the drive makers are filing on their own housings. A supplier selling into those accounts is competing against the customer's own design group. The venting standard's committee is chaired by a filtration supplier rather than an OEM, so the technical seat is held by a parts maker, but the OEMs are building their own claim to the part regardless.

Eaton's leak-check mechanism can be actuated on the assembly line, so the pack can be pressurised or put under vacuum for testing with the valve already fitted. Freudenberg's DIAvent maxFlow replaces the rubber umbrella of earlier designs with a profiled metal spring that snaps fully open at the trigger pressure and closes the opening again once pressure drops. It passes more than 190 L/s at 300 mbar, with the trigger pressure settable between 50 and 200 mbar. Because the mechanism reverses, a fully assembled pack can be tested non-destructively at end of line, which a one-shot burst disc cannot do. Gore's MultiVent opens its larger valve at 50 mbar, passes 50 L/s at 180 mbar and reseals.

PorVent is the exception I found. It states that its vents are tested by NABL-approved external laboratories for IP 66/68/69K, UL 94 V-0 flammability, temperature cycling, salt fog, mechanical impact and vibration, with an IPX7 immersion test run after the vibration test. It is still the supplier's account of the tests and no report is published, but it is the only public case I found where the testing body is named rather than the brand.

A regulation with a date and a component standard turn the valve into a certified part. China's GB 38031-2025 requires no fire and no explosion and adds a bottom-impact test and a 300-cycle fast-charge safety test, and a Chinese group standard specifies the test method for a battery explosion-proof valve. The buyer's question stops being "can you make this" and becomes "can you prove it." Test evidence, certification and traceability become the qualification gate, a different barrier from manufacturing capacity, and they favour suppliers who have already run the tests. The leverage sits in the drafting: the Chinese standard's group was led by a Dongguan precision-electronics firm, so a supplier that helps write the test method knows what the test will be before its competitors do. Capacity is being added ahead of that gate — PUW's two new lines, against a top five that already held 58% of the market in 2024 — a bet on being one of the few suppliers who can pass it, placed against market estimates that disagree by an order of magnitude.

Several designs open part of the flow path at a first pressure and the rest at a higher one. BYD claims a valve that opens part of its relief channel between a first and second preset pressure and the remainder above the second. EVE Power claims a three-stage valve with separate first and second opening pressures, and CPS Technology a burst vent with two valve portions releasing on incremented thresholds. BMW's battery housing valve opens reversibly at a first pressure for equalisation and irreversibly at a higher one to let hot gas out.

Gore measures its moisture figure against "many commercially available dual vents" without naming one. Donaldson calls its degassing "the industry's fastest". Vernay calls VoltaVent an "unparalleled solution". The named benchmarks in this marketing are standards and regulations rather than competing products, which is a fair reading of where the buyer's attention is being directed.