Samsung explains (at last) why Galaxy Note 7 phones kept exploding. Hint: It’s the batteries

Samsung: Aggressive battery design, manufacturing oversights played a part in Galaxy Note 7 debacle

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Batteries in the first batch of Samsung Note 7 devices short-circuited as a result of damage to a separator, a component within lithium-ion batteries that prevents the negative and positive electrodes from coming into contact and generating dangerous amounts of heat, Samsung said in a press conference Monday morning in Korea. The company found that “type B” batteries — batteries in the a follow-up shipment of Note 7 units — experienced component failure for the same reason. Manufacturing oversights including a “thinner separator” design and misaligned of key battery components, Samsung said.

The truth about how and why the Galaxy Note 7 turned into such a fiery, spectacular failure was revealed to the public in a live-streamed press conference on Monday in the company’s home country of South Korea, where Samsung revealed the result of an elaborate investigation into the doomed device and details on what caused Note 7 units to overheat — and in some cases, burst into flame.

Samsung President of Mobile Communications Business DJ Koh, who led the presentation, began by announcing that 96 percent of about 3 million devices sold and activated had been returned. “I sincerely apologize … to all of our business partners,” Koh said. “We thank you for your patience and continuous support.”

What caused the explosions?

Koh said Samsung reviewed every potential cause of the of the Note 7’s defects, including its battery, hardware, software algorithms, manufacturing, and logistics. It retained the services of third parties including the Underwriters Lab safety consulting firm, the Exponent engineering and scientific consulting firm, and Germany’s TUV Rheinland. And it enlisted the help of 700,000 Samsung engineers across the four locations in which it manufactured its phones: Gumi, South Korea; Hanoi, Vietnam; and Huizhou and Tianjin, China.

Together, the parties tested more than 200,000 devices and over 30,000 batteries in a large-scale charge and discharge test facility that tested the impact of several features on overheating, including the Note 7 units’ fast-charging feature, wireless charging, USB Type-C voltage capacity, water resistance, software algorithms, and iris scanner.

Initially, the engineers didn’t observe any hardware or software anomalies, Koh said. But when they turned their focus to the phones’ batteries — which two suppliers custom-engineered for the Note 7, and which featured distinctive voltage specifications — they were able to replicate the overheating and explosions observed in consumer devices.

Engineers determined that “type A” batteries — the batteries included in the first crop of Note 7 devices shipped to market, supplied by Samsung’s SDI unit — short-circuited as a result of battery casing that didn’t have enough room to let the battery expand and contract during recharge cycles. Damage to the separator, a component within lithium-ion batteries that prevents the negative and positive electrodes from coming into contact and generating dangerous heat, occurred as a result, which led to overheating.

And it found that “type B” batteries — batteries in the second shipment of Note 7 units from second recall, designed by Hong Kong-based Amperex Technology — experienced component failure as a result of manufacturing and quality issues that occurred when Samsung increased its order to about 10 million new batteries. Protrusions in the battery were left over from the ultrasonic welding, the company said.

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