Wednesday, January 11, 2017

Remember the Samsung Galaxy Note 7 Fires?

It's looking like it was Samsung's fault and not the battery suppliers.  Samsung mishandled the battery. In retrospect, it has looked like Samsung's fault since fairly early on, when the first units that got battery replacements started to catch fire, too.  The data since then clarifies the picture. 

In the January edition of Electronic Design magazine (which is not at that website, yet), Technical Editor Maria Guerra links to this interesting take down by an independent Quality Engineering consultancy called Instrumental.  They place the blame squarely on Samsung's aggressive design and failure to allow sufficient room around the battery.  One of the key pieces of information is in a footnote to the first paragraph concerning lack of room around the battery.
When batteries are charged and discharged, chemical processes cause the lithium to migrate and the battery will mechanically swell. Any battery engineer will tell you that it’s necessary to leave some percentage of ceiling above the battery, 10% is a rough rule-of-thumb, and over time the battery will expand into that space. Our two-month old unit had no ceiling: the battery and adhesive was 5.2 mm thick, resting in a 5.2 mm deep pocket. There should have been a 0.5 mm ceiling. This is what mechanical engineers call line-to-line -- and since it breaks such a basic rule, it must have been intentional. It is even possible that our unit was under pressure when we opened it.

When you add in that the Lithium ion battery is the common, layered ("jelly roll") design, a failure mechanism starts to emerge.  The battery consists of a positive layer made of lithium cobalt oxide, a negative layer made of graphite, and two electrolyte-soaked spacer layers made of polymer.  The spacers 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 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.  Given that the battery is already on the border of being compressed by design, add in any pressure on the case, perhaps being held in a back pocket while sitting, and the possibility increases that the pressure allows the electrodes to touch. 
What’s interesting is that there is evidence in the design of an intellectual tension between safety and pushing the boundaries. Samsung engineers designed out all of the margin in the thickness of the battery, which is the direction where you get the most capacity gain for each unit of volume.  But, the battery also sits within a CNC-machined pocket -- a costly choice likely made to protect it from being poked by other internal components.  Looking at the design, Samsung engineers were clearly trying to balance the risk of a super-aggressive manufacturing process to maximize capacity, while attempting to protect it internally.
Instrumental's Anna Shedletsky continues:
While we were doing the teardown, Sam wondered, “Samsung engineers are smart. Why would they design it like this?” The answer isn’t a mystery: innovation means pushing the boundaries. For something that is innovative and new, you design the best tests that you can think of, and validate that the design is okay through that testing. 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. 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.

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. Either way, it’s now clear to us that there was no competitive salvageable design.

The design and validation process for a new product is challenging for everyone. In this case, Samsung took a deliberate step towards danger, and their existing test infrastructure and design validation process failed them. They shipped a dangerous product. That this is possible at one of the top consumer electronic companies in the world is humbling -- and demonstrates the need for better tools. Instrumental is building them.
In the magazine column linking to the Instrumental piece, Tech Editor Guerra ponders if more laws are required.  Once Samsung faced up to the reality that they had pushed the envelope too hard and pulled the product off the market, they estimated the losses from the product would total $5 Billion by this March and $5B is a much larger fine than they'd get from any new laws.  It's true that the corporate profits did alright and Samsung didn't lose money for the year, but that's because other products did well enough to cover the $3 to $4B of the Note 7 problems.  Not many companies can lose $4B and be just fine; obviously their financial picture would be very different without the Note 7 debacle. 

Now stop and think of the root cause here.  Instrumental says the battery should have had 0.5mm, or about .020", more clearance.  The phone was pushed into unsafe territory because someone wouldn't allow the phone to get .020" thicker.  That's a bit thicker than most business cards, but does it really matter that much to put a phone on the market that's 20 thousandths thicker, at the risk of $5 billion, lawsuits, and injuries - not to mention the loss of brand prestige?  


  1. While it may be true that Samsung was at fault for not taking into consideration how dangerous these batteries are it remains true that these batteries are dangerous. Maybe we just have to live with it like we live with 30,000 traffic deaths every year. But I feel confident I know with a high degree of accuracy what is dangerous about driving and how to mitigate that with safe driving techniques. But when it comes to these batteries I do not know that they are dangerous until they start self destructing and I do not know which of my electronic devices are likely to kill me. I think every device that has a lithium battery should at the least carry a warning label.

    1. The only issue I have with that is that all batteries are dangerous. They're a fuel tank. The fuel tank on anything is dangerous. How many car gas tank fires are there every year?

      Why then do we hear about Lithium Ion batteries? Mostly because they're the "new hotness" in batteries and they're getting used in everything. The technology has a lot of things going for it that make it a good design fit in lots of places. Some of those places, like the Note 7, will have design deficiencies. But every year, some number of lead-acid car or boat batteries explode, some number of battery packs on power tools (usually NiCd or lead-acid on older tools) explode and so on.

      I think another reason is that it's dramatic for the news media to talk about a cellphone exploding, rather than a car or some carpenter's tool. It's somehow more personal because they can identify with it more.

    2. With all due respect I don't fully agree. Certainly gas tanks are dangerous but we all know that and we assume that responsibility as informed consumers. I doubt that half or even 3/4 of users of products with lithium batteries knew a year ago that these thing would self immolate with no warning. Hoverboards have been responsible for burning down houses and are no longer allowed on airplanes. The worst I have ever heard of the classic D cells (C, AA, AAA, etc.) doing was leak and cause some corrosion to flashlights and other battery powered equipment. I think this new risk is a considerable jump in concern. I'm not saying to do away with them but to better educate and allow informed choice.

  2. Why do I have this vision of some engineer stating in a meeting "We have a potential problem" and some sales or manager type stating something along the lines of "We'll accept the risk"

    ... and now stating something like "Engineering didn't push back hard enough"

  3. I think SiG summed it up pretty good. Why risk the big bucks when a relatively small adjustment to a dimension which might affect the outer dimensions and hence, the aesthetic/industrial design of the product? I think people lose the forest through the trees. The forget that the design of the "product" winds up becoming Millions of products with potential liabilities.

    I just watched "Deepwater Horizon" movie which reminds me of the same thing. Concern for being a few days behind schedule and some cost overruns caused everyone to put the entire rig at risk, the complete investment plus lives. The short term thinking, or short sighted thinking, needs to be kept in check with clear priorities that under pressure remain "givens" and are clearly reviewed by all.

    Shortcuts are dangerous. Whether you want to call them gas tanks or not, they have consequences because of the technology. Warning labels are stupid. Who reads them anyway, or in the case of LiOn batteries, understands them?

    1. I would hope you understand by now, LetsPlay, that the people who take shortcuts are the ones that get promoted up the management ranks. Or haven't you had any management training classes???

    2. I believe that what you saw on the movie about Deep Horizon was the trial lawyer version of what happened. After all if you don't have an act or lack of an act that created liability then you don't get to tap into the billions the Government extorted from the oil company. Just like the billions in the asbestos account to settle lawsuits. I can assure you that one the money is gone the lawyers are gone too and suddenly there are no more people injured by asbestos.

  4. Graybeard, I have to say I really enjoyed this post. This is the kind of problem solving I really enjoy and sleuthing this out was very interesting. It is a very different world that not many people appreciate. Great job! Thanks.

    1. Thanks for the feedback. I also find this sort of stuff interesting. The trade magazines have lots of tear down articles on new hot products, but it's always aimed at just seeing what's inside. This sort of failure analysis is rare, but absolutely necessary.

      A few months ago, we had two old iPhone 3Gses start to get pushed open by swelling batteries. They were about seven years old and we kept them as emergency 911 phones and then just because they're cool computers. Within a few weeks of each other, the batteries popped the cases open. In one case, the battery cracked the phone's case and broke it open; in the other case, it helped the phone roll off an end table and that broke it open. We took them to a battery recycling center.

      It was around the time the Samsung fires were making news and it sensitized me to the story.