Schematic of Samsung Galaxy Note 7 lithium ion battery
Credit: Samsung
Since recall of the Galaxy Note 7,1 96% of 3 million Note 7s have been returned globally. Hard to imagine why the remaining 4% haven't been returned, given their safety record, & the ongoing shutting down of service around the world.2,3
Investigations have included a large number of charge/discharge cycles on 200,000 Note 7 devices & 30,000 Note 7 batteries by 700 researchers. Underlying cause is short circuiting inside Note 7 batteries arising from manufacturing & product quality issues.
Storage capacity of a lithium ion battery, such as the one in your phone, depends substantially on the surface area of the electrodes. To this end, the electrodes are wound around each other, as shown in the diagram above. To prevent short circuits, they have a separator wound between them. Also present, but not shown in the diagram, is insulating tape.
Defects Samsung identified:
● bending of negative electrode by the battery case
● bending of negative electrode due to incorrect positioning in the curve at the thin side of the battery
● high welding burrs on the positive electrode causing it to penetrate the insulation tape (not shown in the schematic above) & separator causing an internal short circuit
● some batteries had missing insulation tapeMore detail in the Samsung report – “Galaxy Note7: What We Discovered”, https://news.samsung.com/global/infographic-galaxy-note7-what-we-discovered
__________
1 Hitchhikers Guide 2 Tech: “Samsung pulls the plug on the Note 7”, https://hhg2tech.blogspot.com/2016/10/samsung-pulls-plug-on-note-7.html
2 ITNews: “Samsung is kicking Galaxy Note 7 users off Aussie telco networks”, http://www.itnews.com.au/news/samsung-is-kicking-galaxy-note-7-users-off-aussie-telco-networks-443170
3 Fortune – “Here’s How Samsung Will Disable Unreturned Galaxy Note 7 Devices”, https://fortune.com/2016/12/09/samsung-kill-galaxy-note-7/
/ Samsung internal short-circuiting internal short circuit batteries battery caused fires Samsung Electronics found internal short circuiting Samsung Galaxy Note 7 batteries caused phones heat up catch on fire catch fire Note 7 launched globally users reported batteries catching on fire Samsung announced global product replacement program swap problematic batteries problems continued device discontinued globally press conference headquarters Seoul South Korea president Samsung's mobile communications business DJ Koh apologised customers retailers business partners invested all efforts substantial resources analyse every aspect failure fully investigate the causes over 700 researchers engineers spent months analysing 200,000 Note 7 devices 30,000 Note 7 batteries devices batteries repeatedly charged discharged simulating incidents in the field incidents caused battery cell focus investigation batteries 96 per cent of 3 million devices sold activated globally returned Samsung conducted internal review independent reviews UL safety science organisation Exponent US-based consulting engineering firm TuvRheinland German-based company batteries sourced two suppliers presentation UL president consumer business Sajeev Jesudas organisation found assembly manufacturing issues batteries suppliers product quality issues batteries higher energy density batteries increase severity battery failure design manufacturing issues batteries field failures Note 7 devices Note 7 handsets lithium-ion batteries arranged in layers positive negative electrodes physical separator between short circuit battery cell damage separator Samsung says it won't happen again South Korean company improved its processes Samsung developed battery check protocol invited researchers academics provide analysis ensure battery safety /
