– One of the worst fiascos in smartphone history was caused not by faulty hardware or software, but by faulty batteries from two different manufacturers, Samsung says. In a Monday press conference in Seoul, the company said early Galaxy Note 7 fires were caused by ill-fitting battery components, the BBC reports. In replacement phones, defects including welding issues and a lack of insulation were to blame, the company said. Samsung issued a recall last year after widely reported cases of the phone catching fire and exploding. It ended up axing its answer to the iPhone and losing around $5.3 billion. "The lessons of this incident are deeply reflected in our culture and process," Samsung mobile chief Koh Dong-jing told reporters. "Samsung Electronics will be working hard to regain consumer trust," Koh said. Samsung says that to verify the cause of the fires, 700 researchers tested more than 200,000 phones and 30,000 batteries, the AP reports. Koh told reporters that there was no sign that the very high energy density of the Note 7 batteries had made them prone to overheating, but the episode provides a "chance to strengthen the safety of lithium-ion batteries for the entire industry, not only us." Samsung says it has recovered 96% of the 3 million Note 7s that were sold, and it hasn't decided yet whether it is going to reuse parts. Analysts tell Reuters that Samsung has probably done enough to reassure consumers, but it will be a different story if there are any problems with its Galaxy S8, which is expected to be in stores by April.

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Image copyright Reuters Image caption The Galaxy Note 7 had been well-reviewed but dozens of the phones overheated 
  
 Samsung's probe into its Galaxy Note 7 fiasco has found that the overheating and burning of the phones was caused by faults with their batteries. 
  
 The firm had axed its iPhone rival in October last year after an earlier botched recall and re-release. 
  
 The recall is thought to have cost $5.3bn (£4.3bn) and was hugely damaging for the South Korean firm's reputation. 
  
 On Monday, Samsung said that neither software nor hardware were at fault, only the batteries. 
  
 Internal and independent investigations "concluded that batteries were found to be the cause of the Note 7 incidents", the South Korean technology giant said in a statement. 
  
 So what went wrong? 
  
 The company said that errors both in design and manufacturing affected batteries by two different manufacturers. 
  
 According to the findings, the problems centred on insufficient insulation material within the batteries and a design that did not give enough room to safely accommodate the batteries' electrodes. 
  
 Image copyright Samsung Image caption Some batteries were affected by a design error ... 
  
 Image copyright Samsung Image caption while others suffered from insulation problems 
  
 Samsung said it was "taking responsibility for our failure to ultimately identify and verify the issues arising out of the battery design and manufacturing process". 
  
 The smartphone giant did not name the battery suppliers during their Monday presentation, though last year had identified them as their affiliate Samsung SDI and Chinese company Amperex Technology. 
  
 Samsung said it did not plan to take legal action and that it accepted responsibility for asking the suppliers to meet certain specifications. 
  
 "Samsung has done what they needed to do for now but the true test will need to happen over time," analyst Bryan Ma of IDC told the BBC. 
  
 "If successive products can be delivered consistently without incident in the next year or so, then they will be in a better position to regain consumers' trust." 
  
 Image copyright AFP Image caption Some reviews had described the Note 7 as being the best Android handset to date 
  
 Launched in August 2016, Samsung's Note 7 device was marketed as a large-screen top-end device and positioned as a rival to Apple's iPhone. 
  
 But in September, Samsung had to recall about 2.5 million phones after complaints of overheating and exploding batteries. 
  
 The firm insisted that all replaced devices were safe. However, that was followed by reports that those phones were also overheating. 
  
 Lessons to learn 
  
 The company said there would be no repeat of the fires in future devices such as the upcoming S8. 
  
 "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." 
  
 The firm also said it would not unveil its upcoming Galaxy S8 phone at the Mobile World Congress in Barcelona, as had been expected, suggesting the flagship model's launch may be later in the year. 
  
 The head of the firm's smartphone business, Koh Dong-jin said the phone would not get a launch event at the event in Barcelona in February unlike previous Galaxy S smartphones. 
  
 Samsung Note 7 - how events unfolded 
  
 24 August: The first report of a Note 7 "exploding" appears in the news, soon followed by images of more smouldering Samsungs. 
  
 2 September: Samsung announces a voluntary global recall of 2.5 million Note 7 phones, citing faulty batteries. It offers refund or replacement. 
  
 8 September: US aviation authorities and many airlines tell passengers not to turn on or charge the phone on planes. 
  
 9 September: The US Consumer Product Safety Commission tells people to stop using the phone and on 15 September issues a formal recall. 
  
 5 October: Reports emerge of a replacement Note 7 overheating on a US flight. In the following days more reports appear and major US carriers stop selling the device or issuing replacements. 
  
 11 October: Samsung permanently stops production of the Note 7. It tells people to turn them off and stop using them. ||||| FILE - In this Sept. 2, 2016 file photo, a Samsung Electronics' Galaxy Note 7 smartphone is displayed at the headquarters of South Korean mobile carrier KT in Seoul, South Korea. Samsung Electronics Co.... (Associated Press) 
  
 FILE - In this Sept. 2, 2016 file photo, a Samsung Electronics' Galaxy Note 7 smartphone is displayed at the headquarters of South Korean mobile carrier KT in Seoul, South Korea. Samsung Electronics Co. said Monday, Jan. 23, 2017, that problems with the design and manufacturing of batteries in its Galaxy... (Associated Press) 
  
 SEOUL, South Korea (AP) — Samsung Electronics said Monday 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 Aug. 2, in one of its worst product fiascos ever. 
  
 The company said 700 hundred 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. 
  
 U.S. 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. 
  
 It was unclear to what extent the battery maker was responsible for those problems: Samsung said only that it had provided "targets" for the batteries. 
  
 "We suggested that the Note 7 has innovations and a compact design and a 3500 mAh (battery) but we did not know how to make the separators within (the battery) or how many millimeters thick they should be," Koh told reporters. 
  
 That may suggest a breakdown both in communication between Samsung and its suppliers and in quality control and testing. 
  
 In other batches of batteries from a second manufacturer, presumably ATL, the researchers found welding defects and a lack of protective tape in some battery cells. 
  
 Patrick Moorhead, president of Moor Insights & Strategy, said the odds of two different suppliers having issues with the same phone are extremely low. 
  
 Though Samsung faulted the batteries from its suppliers, it said in a statement "we provided the target for the battery specifications for the innovative Note 7, and we are taking responsibility for our failure to ultimately identify and verify the issues arising out of battery design and manufacturing." 
  
 Koh said Samsung would treat the event as a "chance to strengthen the safety of lithium-ion batteries for the entire industry, not only us." 
  
 Analysts said the root cause of the fires remains unclear. "Samsung said the weaknesses could make the phone prone to catch fire. That I understand but what did trigger fires in such conditions? Did they discuss if there is another cause? No," said Park Chul Wan, a former director of the next generation battery research center at the state-owned Korea Electronics Technology Institute. 
  
 Recalls of the Note 7s began in September after reports emerged that some of the phones were overheating and catching fire. At the time, Samsung blamed a flaw in batteries from one of its two suppliers, without saying which manufacturer was to blame. 
  
 In October, Samsung dropped the phone for good after new Note 7s with different batteries issued as replacements also were found to be catching fire. It estimates the problems will cost it at least $5.3 billion through early 2017. 
  
 The company has recalled 3.06 million Note 7 phones. About 4 percent, or 120,000 units, of the recalled Galaxy Note 7, are still not returned. 
  
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