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Galaxy Note 7 fires were caused by over-ambitious design, engineers find

Updated Dec 5th, 2016 1:51PM EST
Galaxy Note 7 Recall

We’re still waiting for an official verdict from Samsung over what caused the Galaxy Note 7 debacle. Given that the company got it wrong the first time it recalled its flagship smartphone, you can excuse it for taking its time to investigate things.

But Samsung’s ongoing investigation hasn’t stopped one engineering firm from finding a Galaxy Note 7, setting up a couple fire extinguishers, and tearing the phone down to do its own analysis.

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Instrumental is a manufacturing technology firm that realized the void of information on the Galaxy Note 7 recall made for a perfect PR opportunity. The company’s engineers tore down the phone to expose the battery in between, and then wrote a blog post analyzing the (many) design problems with the battery:

“What we found was surprising: the design can compress the battery even during normal operation (see footnote).

Why does this matter?  The Note 7’s lithium-polymer battery is a flattened “jelly-roll” consisting of a positive layer made of lithium cobalt oxide, a negative layer made of graphite, and two electrolyte-soaked separator layers made of polymer.  The separator layers allow ions (and energy) to flow between the positive and negative layers, without allowing those layers to touch.  If the positive and negative layers ever do touch, the energy flowing goes directly into the electrolyte, heating it, which causes more energy to flow and more heat — it typically results in an explosion. Compressing the battery puts pressure on those critical polymer separator layers that keep the battery safe.”

In short, there’s two design problems here: the battery is too susceptible to a small amount of pressure, and there wasn’t enough tolerance around the battery in the phone, so regular use caused the rest of the phone to compress the battery.

Instrumental also hints that Samsung engineers were probably aware of the fine line they were walking from the start. The battery rests in a custom CNC enclosure, an unusual and costly design choice that’s made to protect the battery from the rest of the phone. Only, it didn’t work.

Another interesting observation from the teardown is that even if the Note 7 hadn’t had an explosion problem, customers might have seen bad long-term effects, the same sort of problems that have plagued the iPhone 6 Plus and ‘Touchgate‘:

“If the Galaxy Note 7 wasn’t recalled for exploding batteries, Sam and I believe that a few years down the road these phones would be slowly pushed apart by mechanical battery swell.  A smaller battery using standard manufacturing parameters would have solved the explosion issue and the swell issue.  But, a smaller battery would have reduced the system’s battery life below the level of its predecessor, the Note 5, as well as its biggest competitor, the iPhone 7 Plus.”

The conclusion from the teardown probably won’t shock anyone: in the hunt to make the Galaxy Note 7 the best phone on the market, Samsung’s engineers flew too close to the sun. It wasn’t some critical mistake that sunk the Note 7, just engineering tolerances being pushed to the limit.

Chris Mills
Chris Mills News Editor

Chris Mills has been a news editor and writer for over 15 years, starting at Future Publishing, Gawker Media, and then BGR. He studied at McGill University in Quebec, Canada.

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