Samsung has revealed early this year the results of its in-depth laboratory tests on the root cause(s) of the thermal runaway-categorised battery breakdowns. Quoting from the Recode coverage, the evaluation project "involved 700 dedicated staff testing 200,000 phones and 30,000 additional batteries" and "was also validated by similar findings by the three outside firms it brought in to investigate (UL, Exponent, and Germany’s TUV Rheinland)."

As I mentioned earlier, Samsung initially used two different battery suppliers for the Galaxy Note 7, its own Samsung SDI subsidiary, along with an independent company called ATL. Samsung's initial belief was that SDI-sourced batteries were solely to blame. Therefore, the company initially directed SDI battery-inclusive Galaxy Note 7 owners to swap out their handsets for ATL battery-based replacements. But then ATL battery-inclusive handsets began combusting, as well, prompting a full-scale recall.

The two different batteries, according to Samsung, had two different associated failure mechanisms.

20170718_EDNA_Samsung-Note-7-infographic (cr) Figure 1: Samsung's Galaxy Note 7 analysis. (Source: Samsung)

The company's initial analysis of its own SDI subsidiary's battery flaw, "The plates inside the SDI battery were too close to each other near its rounded corners, making it vulnerable to a short circuit ... and the battery also had defects in its insulating tape and the coating of its negative electrode," ended up not being too far off the final mark:

For the first battery, Samsung says a design flaw in the upper right corner of the battery made the electrodes prone to bend and, in some cases, led to a breakdown in the separation between positive and negative tabs, causing a short circuit.

And what about the ATL-sourced batteries (referred to below as "battery B")? A manufacturing rush to fill the void caused by the abandonment of Samsung SDI as a supplier was the root cause, here, Samsung believes, not any fundamental flaw with the design of the "phablet" itself:

Samsung believes there was nothing wrong with the design itself, but says a manufacturing issue led to a welding defect that prompted that battery to also short circuit and ignite.

Samsung said that its design for the Note 7, while demanding on its battery suppliers, was not unreasonable or the reason why the batteries failed. The issues with battery B, Samsung said, were tied to the fact that the supplier tried to quickly increase its production after battery A was pulled off the market.

“We believe if not for that manufacturing issue on the ramp [of battery B], the Note 7 would still be on the market,” Samsung Electronics America head Tim Baxter told Recode.

20170718_EDNA_Samsung-8-point-battery-check (cr) Figure 2: 8-point battery safety check. (Source: Samsung)

Going forward, Samsung is instituting an eight-point plan in the hopes of avoiding more multi-billion dollar recall and programme cancellation expenses, not to mention owner hassles, associated property damages and the resultant long-term blight on the Samsung brand:

Samsung’s new eight-step battery safety check includes: durability testing, visual inspection, X-rays, charge and discharge tests, tests of total volatile organic compounds (TVOC), disassembling tests, accelerated usage tests, and open circuit voltage tests.

Many of these steps, including the first three listed above as well as open circuit voltage tests, were conducted on earlier devices; but Samsung says the testing is now “enhanced,” and will be conducted with increasing frequency. For example, it says it has raised its internal standards for the visual inspection phase.

I commend Samsung on its thorough analysis and results disclosure, not to mention its too-rare-these-days contrite apology, and hope that this situation has taught the company an expensive but enduring lesson. I hope, too, that its competitors have learned the same long-term lesson by osmosis. Customer requests coupled with competitive pressures are remarkably effective in producing engineering breakthroughs, but at the end of the day, you ignore the fundamental laws of physics at your peril. Per my five-point essay back in early January:

  • Thinner isn't always better
  • Increased performance and increased battery life are at odds
  • Faster charging = more heat and stress
  • System layout is critical
  • Manufacturing care is also critical

Your thoughts, readers?

First published by EDN.