Samsung Reveals Cause of Galaxy Note7 Battery Fires, Explosions

NEWS ANALYSIS: Samsung President DJ Koh described in detail the manufacturing defects in rechargeable batteries that caused some of its Galaxy Note7 big-screen smartphones to burn or explode.

Samsung Note7 Defects

Samsung electronics has taken the extraordinary step of announcing exactly what was wrong with the Lithium-ion batteries that powered the Galaxy Note7 device, how the failures occurred, and what the company will do to ensure it doesn't happen again. The announcement took place during a press conference at Samsung headquarters in Seoul, South Korea Jan. 22 by division president DJ Koh.

He started by apologizing for the inconvenience to customers, resellers and others who were affected by the problem. Then he went into a detailed explanation of the testing the company carried out to determine the cause and to determine whether the faults were with the phone or the battery installed in it.

According to Koh, the phone itself and its software did not seem to be at fault. Instead, he described a pair of faults with the batteries that powered the phone. The first fault started showing up in Note7 handsets in the late summer of 2016. The second set happened in the replacement handsets that were supposed to fix the problem with the first set.

The initial problem happened when the electrodes inside of the battery were manufactured incorrectly so that the negative electrode was bent in the top corner of the battery assembly so that the electrodes were close enough to touch, causing a short circuit.

Normally those electrodes are kept apart by a separator to ensure that a short can’t take place. Exacerbating the problem, some of the electrodes were improperly located within the battery so that they were in a part that curved, again allowing electrodes to touch.

The flaws with the second round of batteries were the result of a different manufacturing defect. There, a welding burr on the positive electrodes was large enough that it broke through the insulating tape and the separator allowing a direct contact between the positive and negative electrodes.

The problem was exacerbated in some batteries because required insulating tape was insufficient or simply missing, which would have increased the chances of a short circuit.

Because the Galaxy Note7 does not have a replaceable battery, it was impossible to simply send out new batteries to customers. Such replaceable batteries would have been an option for previous versions of Samsung’s Galaxy series phones.

However, the market pressure to make the phones as slim and light as possible, but with more features than Apple’s iPhones ensured that the batteries would have to be sealed into the case just like in Apple’s phones.

The energy density of the batteries used by Samsung was a key factor in bringing about the battery failures. Lithium-ion batteries are already notorious for being sensitive to failure because of manufacturing defects.

They are sensitive because a significant amount of electrical energy can be stored in a very small place. Impurities in the chemicals used in those batteries have been causing problems for years.

Wayne Rash

Wayne Rash

Wayne Rash is a freelance writer and editor with a 35 year history covering technology. He’s a frequent speaker on business, technology issues and enterprise computing. He covers Washington and...