Samsung has finally released the results of its investigation into the cause of the Galaxy Note 7 fires. Speculation had earlier pinned down the battery as the cause of the problem, although the official report comes as a surprise by claiming that each of the battery suppliers had completely different defects.
Lithium-ion batteries are manufactured with positive and negative electrodes that are kept separated by a conductive material. This allows electrons to pass between the two and generate current. Allowing the two electrodes to touch accelerates this chemical process, which leads to a short circuit and the entire battery to burst into flames. Which is what happened in the Note 7’s case.
The first batch of batteries suffered from a deformation of the battery casing that caused the folded electrodes to be pressed together. This was enough to short the battery and ignite the entire device.
According to Samsung, engineers had discovered the problem with the first batch of batteries after the initial recall. The company was comfortable with switching to the second batch after an inspection revealed that the original defect was not present.
Instead, a manufacturing error allowed the welding to puncture the separator between the battery electrodes. The result of this was the smartphone bursting into flames as well.
Some 700 Samsung engineers tested some 200,000 devices and 30,000 standalone batteries before concluding that it was the batteries. While these may have been manufacturing errors, some experts believe that this is a result of moden smartphone design aesthetics. Companies like Samsung are pushing technology to the limits by attempting to draw more power from thinner batteries; and are likely to run into this issue again in the future.
[Source: Consumer Reports]