SEOUL, South Korea (AP) – Samsung Electronics said Monday, January 23, that tests of more than 200,000 Galaxy Note 7 smartphones found defects in two sets of batteries from two different manufacturers that made the devices prone to catch fire.
Samsung’s mobile division president, Koh Dong-jin, ruled out any problems with other aspects of the Note 7, either in its hardware or its software.
He said Samsung would use what it learned from its investigations to improve lithium ion battery safety for the industry, though analysts questioned if the company had really gotten to the heart of the problem.
Samsung discontinued the Note 7 just two months after it was launched on August 2, in one of its worst product fiascos ever.
The company said 700 researchers and engineers tested more than 200,000 devices and more than 30,000 batteries and replicated what happened with the Note 7 phones trying to pin down why some of the phones were overheating. US companies UL and Exponent also examined the batteries supplied by South Korea-based Samsung SDI and China-based Amperex Technology Ltd., or ATL.
The German company TUV Rheinland analyzed the Note 7 supply chain as part of the investigation, Samsung said. The Galaxy Note 7 featured one of the biggest battery capacities so far for smartphones at 3,500 mAh, or milliampere hour, which gave it the highest energy density of all Samsung’s devices. However, Koh said Samsung and the outside inspectors found no evidence that the high energy density alone had made the phones prone to overheating.
Rechargeable lithium batteries are more susceptible to overheating than other types of batteries if they are exposed to high temperatures, are damaged or have manufacturing flaws.
A highly technical explanation of Note 7 problems boiled down to the relatively large battery cells not fitting well into their pouches, with not enough insulating material inside. In batteries by one manufacturer – likely Samsung SDI – used in the phones in the initial Note 7 recall, inspectors found damage to their upper corners. That, combined with thin separators and high energy density, caused the phones to overheat.
The cell-pouch design of the battery did not include enough room to safely accommodate its electrodes – another flaw.