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Samsung Galaxy Note 7 fires caused by battery design flaws and manufacturing defects

24 January 2017

Samsung Galaxy Note 7 fires and explosions were caused by defects in the smartphone's battery, and the company has now released details of its investigation into the issue.The South Korean tech giant said that leading industry consultancy groups UL, Exponent and TUV Rheinland also conducted investigations into the problem.

The defects have cost the group at least $5 billion and it had to issue two recalls for the Galaxy Note 7 - the first in September and the second in October 2016.

“We look forward to moving ahead with a renewed commitment to safety. The lessons of the past several months are now deeply reflected in our processes and in our culture,” Samsung said in a statement.

The group found separate problems with two different batteries used in the Note 7. It sealed a sizable 3,500mAh lithium-ion battery into a 7.9mm thin smartphone, but half of the Note 7 batteries were made by its subsidiary Samsung SDI and didn’t properly fit into the Android phone.

The subsequent overheating caused the first round of battery explosions and fires throughout August and September.

The investigating team found there was an issue with the design in battery A. The problem: Not enough room to allow for the expansion of its electrodes, which happens during the normal charge and discharge cycle of the battery.

Samsung’s own explanation is that “the negative electrode was deflected in the upper right corner of the battery,” which is an abnormality in the design. In a normal battery, the positive and negative electrodes are properly separated, and the negative electrode is not deflected nor is it touching the positive electrode.

An additional contributing factor, according to Samsung was the tip of the negative electrode was incorrectly located, resulted in short-circuiting of the battery.

Independent agency Exponent said the thermal failure in battery A was caused due to “unintended damage to the negative electrode windings consistently in the corner of the cell.” This was due to a design flaw in the cell pouch and said there was not enough space to accommodate the electrode assembly, thus increasing risk of failure.

Another investigation by UL found signs of an internal short circuit (ISC) at the upper right corner of the cells from 6 damaged devices. This report also found a pattern of deformation at upper corners of the battery. The agency blames factors in battery manufacturing and assembly for the failure of the Note 7.

Samsung relied on a different manufacturer for Battery B, the second batch of batteries installed in new units of the Note 7 sent out to replace the original ones. In this case there were problems with the manufacturing quality and safety norms were ignored.

Samsung’s own report says there were high welding blurs on the positive electrode, which caused damage to the insulation tape and separator, and once again the positive electrode was touching the negative one, resulting in a short-circuit. Additionally a number of batteries were missing insulation tapes, which made the problem worse.

The report by Exponent blames welding defects and says some cells had no protective tape over the positive electrode tab, which resulted in the failure and short-circuiting. UL’s analysis also blames welding defects in the battery, along with poor alignment and inconsistent shape of insulation tapes for the problem.

To ensure the problem does not happen again Samsung has taken a number of measures.
It announced an enhanced 8-Point Battery Safety Check for safety of batteries used in their phones. The list includes enhanced durability, visual inspection, X-ray test, disassembling test, charge and discharge test, TVOC (Total Volatile Organic Compound) test and accelerated usage test.

Samsung has also set up a Battery Advisory Group, which consists of external advisers, academic and research experts, to ensure the problems do not happen again. Members of this group include top materials science professors from the University of Cambridge, UC Berkeley and Stanford University.

Samsung says that 96% of the 3 million Galaxy Note 7 phones sold have been returned worldwide, but US carrier Verizon said that ‘thousands’ of its customers are still holding onto the phone on its network. The phone is banned on airplanes and, for several months, there was a PR-devastating flight announcement about the ban before every US plane took off.
Samsung’s reputation as the top Android phone maker has been damaged by the issue.

The Samsung Galaxy S8 will be its new flagship handset for 2017, and is set to arrive in March/April. Samsung’s press conference and announcement were designed to reassure the public that safety is now its top priority and these problems are now in the past.

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