Samsung Knew a Third Replacement Note 7 Caught Fire On Tuesday and Said Nothing (theverge.com)

If you had started to feel sympathetic for Samsung, or safer with the Note 7, its latest flagship smartphone, don't be. Another replacement Samsung Galaxy Note 7 has caught fire, making it three of such incident this week alone. Read how poorly Samsung has dealt with the situation, via The Verge: This one was owned by Michael Klering of Nicholasville, Kentucky. He told WKYT that he woke up at 4AM to find his bedroom filled with smoke and his phone on fire. Later in the day, he went to the hospital with acute bronchitis caused by smoke inhalation. "The phone is supposed to be the replacement, so you would have thought it would be safe," Klering told WKYT, saying that he had owned the replacement phone for a little more than a week. "It wasn't plugged in. It wasn't anything, it was just sitting there."The most unsettling part is that Samsung knew of Klering's phone, and didn't say anything.

Comments

Re: Samsung is starting to behave like Tesla

[geoskd]

So what is the real culprit here? I thought it could have been from using the wrong charging IC or someone in the battery department changing the chemistry and not telling the EEs. But they are catching fire without charging.

Lithium chemistry batteries are finicky little bastards. They are not just dangerous from over-charging (or charging too fast), but also from over-discharging and discharging too rapidly. If they are drawing 1A from a battery that is only designed to handle 1/2A, or worse, if their control circuitry allows the battery to fall below a minimum voltage, then the batteries can go into runaway thermal overload. The worst part is that all of the various factors change with pressure, so at 35k feet, you have to be far more conservative with the batteries to avoid a fire. With Li batteries, getting the extra capacity out of them can be very dangerous, and it only take a small error to end up with fires or explosions. Worse still parameters can vary widely from individual battery to individual battery and is made far worse when the batteries are sloppily made.

It should also be noted that it is unlikely that the phones have a dedicated battery monitoring chip as these cost a couple bucks, even in large quantities, and all they really are is a small microprocessor and a couple cents worth of transistors. Since cell phones already have the processor, they just use that, and add the couple of small transistors they need to handle the charging and discharge monitoring.

The root problem could be as simple as a badly chosen set of constants for cutoff voltage and thermal protection, or could be more insidious, such as a thermal protection sub-routine that doesn't work properly because at shutdown the processor looses power and reboots, thus continually drawing power from the battery.