Why water leaks are a headache for the EV boom

Swiss instrument supplier Inficon has been detecting air leaks for years — on air conditioners, refrigeration, airbags and transmission housings — to look for manufacturing flaws and toxic chemicals. Now the auto industry is asking the company to find leaks in a booming new segment: electric vehicle batteries.

And it's not about air getting out. It's about the possibility of water getting in.

Rainwater splashing into a battery enclosure from the road surface or lake water seeping in while the owner of an electric SUV launches a fishing boat can potentially ruin a big battery.

The question facing automakers and battery suppliers all over the world now is how to make sure something the size of a mattress hasn't ended up with a tiny leak in its seal during mass production.

Inficon's solution is to apply a technology it's been using for years on other products to batteries coming down the assembly line. It pumps helium into the battery packs, and then robotic sensors move in like airport drug-sniffing dogs to detect any sign of the gas escaping.

The application may seem like a no-brainer for a company that's been using helium tests for years.

The devil is in the details, said Thomas Parker, Inficon's manager of North American automotive sales. Some technical issues are not yet resolved in the young industry segment. Chief among them: Can a battery pack tolerate even a slight leak, or does it need to be manufactured to the precision of a NASA part?

General Motors last year recalled more than 800 new Hummer EV pickups and BrightDrop EV600 vans because their battery seals could let in water.

"We're educating customers to make sure the leak test fits the application, in terms of what the battery is and how it's going to be incorporated into the vehicle, and also in terms of the planned production rate for the batteries," Parker said.

So far, there are no specific industry guidelines on how precisely leaks should be controlled. SAE, the industry's engineering body that gives guidance on technical matters like this, is looking into the question but has not yet issued any specifications.

Luckily for the industry, mass production of EV batteries is still a relatively new phenomenon, which means their factories are still being constructed for the most part. Parker believes that while leak testing systems can be introduced into an existing production line, incorporating them into new factory project blueprints is a safer bet.

"The auto industry doesn't want to overengineer this, but it has to be safe," he said. "There's always a balance for everyone to be profitable. But so much new investment has been going into EVs and battery manufacturing that there hasn't been time yet to work out all these details. That will change over time."