Design engineering firm: Galaxy Note 7 tolerances not enough for battery
The Galaxy Note 7’s battery smothered Samsung’s 2016. Burst after fiery burst led to a drawn-out, multi-step recall and financial repercussions that will echo for some time. But did Samsung do its due diligence in determining the problem and communicating it to the public?
Its official line, via its UK arm, was that some of the batteries’ intake and output points were put too near to each other. That allowed charge and discharge streams to merge, causing the thermal runaway. Other sources from within the company have pointed across the board from cell fabric tension to shoddy work with insulation tape.
Anna-Katrina Shedletsky, founder and CEO of design engineering firm Instrumental, decided to look into why an assembly process couldn’t have been tweaked instead of what had actually happened.
In a teardown and analysis of a single unit, her team had found that normal operation of the Galaxy Note 7 allowed the phone to expand and encroach upon the battery. This put inward pressure against the positive cell layer and the negative cell layer, along with the insulating layers in between. When these layers are squeezed too closely, the insulation essentially becomes useless as the charged layers begin to feed energy into each other and ramp up the temperature, thus risking fumes and explosion.
The fact that Samsung decided to fit a 3,500mAh battery into a fairly small space amplifies the potential impact — whether it was safely able to is not up for debate.
“Battery testing takes a notoriously long time (as long as a year for certain tests), and thousands of batteries need to be tested to get significant results” Shedletsky said. “It’s possible that Samsung’s innovative battery manufacturing process was changing throughout development, and that the newest versions of the batteries weren’t tested with the same rigor as the first samples.”
The designed tolerance for the battery slot beside the pulsing PCB, at some points down below 0.1mm, also doesn’t help. Hell, there wasn’t even any breathing space on the Z-axis where there should’ve been at least a 10 percent allowance.
Instrumental determined that even if Samsung kept the Note 7 on the market, many customers would see their phones warp over time. On the other hand, we infer that Shedletsky believes that the chaebol would’ve needed to install a battery with less capacity than of the Galaxy Note 5 and the iPhone 7 Plus in order to keep the smartphone’s design, as it was, safe.
“Either way, it’s now clear to us that there was no competitive salvageable design,” Shedletsky concluded.
Samsung made it a clear point to load all the useful technology it could that it didn’t for the Note 5 into its 2016 powerhouse release: expandable memory, some form of waterproofing, a super-capable stylus, curb-appeal looks and a gas tank to let it chug. The company tried to innovate where it could to make as little compromise as possible.
What resulted was the largest compromise in the consumer mobile market in recent history.