Why Samsung Doesn’t Know Exactly What Caused Its Phones To Catch Fire

It may take months before the Korean electronics giant has an answer.

Six weeks since Samsung first recalled its once-ballyhooed Galaxy Note7 smartphones, and more than three weeks since it stopped selling them entirely, the company still doesn't know what, precisely, is causing its flagship phone to catch fire. For the Korean electronics giant, it has spelled disaster. The company stands to lose $17 billion in revenue, even as its reputation plunges in key markets across the world.

An official accident report Samsung filed with the Korea Agency of Technology, which BuzzFeed News obtained, confirms the company still doesn't know what led to 35 reported cases of battery-induced Note7 damage around the world. According to the document, despite an initial diagnosis of "marginal errors" during the battery cell manufacturing process that ultimately resulted in a heat-producing short circuit in Note7 phones, it's unclear if that is the cause behind all the fires. Samsung confirmed the report is authentic, but declined to comment on its ongoing investigation.

In other words, one of the 20 richest companies in the world, a global conglomerate worth half a trillion dollars, can't quickly figure out what's causing one of its flagship products to reportedly set cars on fire. Even though Samsung is bleeding money and trust with each day it doesn't have an answer, it very well may be months before the company has an explanation — and can try to assure consumers its next phones won't have the same problem.

"If I was Samsung, I'd be gathering phones like crazy. Those have the best clues." 

None of this is surprising to Glen Stevick, a mechanical engineer, failure analyst, and the founder of Berkeley Engineering and Research, which has studied dozens of lithium ion fires. Stevick, who helped determine what made the Deepwater Horizon explode, said that getting to the bottom of a major consumer recall case like this takes time — six months to a year "to know everything." That would, by certain standards, be quick: It took nearly two years after the first reports of problems with the lithium ion batteries in the Boeing 787 Dreamliner for the National Transportation Safety Board to release its official report.

That's because, according to Stevick, these are huge undertakings, and not ones that just take place in a lab. Before Samsung's engineers can start to analyze the exploding phones, the company has to collect them.

"If I was Samsung, I'd be gathering phones like crazy," Stevick said. "Those have the best clues."

That means not just the 35 phones that caught fire, but hundreds of other Note7s in various states of use. Only then, said Stevick, can "you start slicing those batteries and putting them under an electron microscope. Gradually the issues will appear."
What Samsung's failure analysis team would be looking for, Stevick said, are dendrites: microscopic lithium fibers that can grow — vine-like — over time from the anode (negative pole) of the battery, across a thin separator, to the cathode (positive pole). When the two poles connect, watch out: You've got a short circuit and a potential fire.

The two main culprits behind out-of-control dendrite growth, charging too deeply and charging too fast, happen to be correlated with features consumers want: namely, better battery life and faster phone recharging. But it's not as simple as blaming one or the other. Perhaps both are a problem. Perhaps the electrolyte separator — which keeps the anode and cathode apart — is too thin and therefore too easy for the lithium tendrils to bridge. Or perhaps the design of the battery case squished the battery too much, again making it easier for the two poles to connect.

Or maybe, as Samsung initially claimed, there were battery manufacturing issues, things like, as Stevick put it, "someone leaving a door open in the clean room," allowing in dust that could lead to a short circuit. Maybe that was a one-time mistake, affecting only a limited set of batteries, that has since been solved. Or maybe not.

Ruling out all of the potential causes, and their permutations, simply takes time. And plotting these issues to a predictive curve is a major challenge, Stevick said, one that can take carefully analyzing hundreds and hundreds of phones.

"Those things can overlap on you," Stevick said, "And you can be all over the place trying to fix it. It isn't easy."

Jihye Lee contributed to the reporting in this story.

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