Samsung Electronics, which has been struggling to restore consumer trust after some of its flagship Galaxy Note 7s catching fire, saw battery defects as the root cause of fires.
In a special press conference in its headquarters in Seoul, Samsung said the mix of thin battery design and other manufacturing issues caused the Note 7s to catch fire or explode, which led to property damages and injuries.
Batteries, carried by the fiery gadgets, had thin separators, which insulate the cathode from the anode. It raised a possibility for the contact of the positive and negative layers, which result in internal short circuit.
Aggressively thin battery had been estimated by experts as one of the main reasons the flagship Samsung phone was overheated. Insufficient physical room can induce the positive and negative electrodes to touch and spark.
Deformation was also found in the upper corners of the defective batteries, according to teardown investigations by two U.S.-based firms UL and Exponent.
Higher energy density to put more power inside a small area of battery had been cited as one of potential causes, but the research firms fell short of confirming it as the main reason.
Sajeev Jesuda, the UL’s executive, said in the press conference that higher energy density can exacerbate the severity of battery failure in “general” terms.
No hardware and software issues were discovered from the fire-prone devices, but the battery had manufacturing errors such as inadequate welding, the missing insulation tape and abnormally tall bumps that destroy separators and insulation tapes.
Kevin White, a principal scientist at Exponent, said welding defects lifted the possibility for short circuit though no deficiencies were found in the pouch of batteries supplied by one of two Samsung subcontractors.
Batteries of the ill-fated devices were supplied by Samsung SDI, Samsung’s affiliate, and Amperex Technology Ltd. (ATL), a Hong Kong-based company which makes products in China.
Samsung initially found an isolated issue with its affiliate’s battery cells, allowing the ATL to manufacture batteries used for replacement phones. Following the additional explosion with replaced devices, the company permanently stopped production.
Note 7s were launched in August last year. Samsung was shortly thrown into embarrassment as multiple gadgets, set on fire without any external cause, were reported.
In September, the world’s largest smartphone producer by sales issued a global recall of about 2.5 million Note 7s, but continued reports of replacement phones catching fire forced Samsung to discontinue the product in October.
Samsung hired third-party research firms more than three months ago for its independent investigation, divulging the findings on Monday.
The Germany-based TUV Rheindland analyzed the logistics and assembly processes of Samsung factories in South Korea, China and Vietnam to find potential factors that affect battery safety, but no fault was discovered.
Holger Kunz, executive vice president of the German firm, told reporters that its supply-chain analysis showed no specific weakness, concern or obvious danger affecting battery safety integrity. Enditem