For ease of explanation, SDI made battery A (faulty), while Amperex made batteries B (good) and C (faulty). Samsung, in its rush to prevent more fires from battery A-equipped devices (none were attributed to battery B at that time), issued a voluntary recall and supplied battery B devices – most of which unfortunately contained a new battery C that was faulty in different ways to battery A.
To explain the issues, one needs to understand the construction of a lithium-ion “jelly roll” battery. It starts as a long flat sheet comprising layers of insulator, lithium foil (anode), electrolyte, cathode, and aluminium foil (outer container). The anode and cathode convert the electrolyte energy and have “taps” (positive and negative contacts) ultrasonically welded to them. The flat sheet is folded (rolled and flattened) and it is sealed up.
The problem is that when the anode and cathode layers touch, usually via cell puncture or corner damage from dropping, a fire can occur. With modern devices, it is less likely that overcharging or other environmental issues can cause fires.
Battery A had some right top corner deflection, meaning the edges of the roll were deformed and some could touch when expanding as they do.
Battery C was different. In the rush to make more batteries, the ultrasonic welds that hold the taps onto the anode and cathode protruded up to 80 microns over acceptable limits and after repeated charging (causing expansion and contraction) penetrated the insulation, causing a fire. In addition, critical insulation tape was left out of some batteries.
So, there you have it – three million Galaxy Note7 devices literally went up in smoke. In fact, 220 faulty batteries of type A prompted the recall; the second was due to 119 of battery type B. The quantum would have been much higher if the recall had not been swift.
Apart from the battery itself, Samsung wanted to confirm that the following items did not contribute:
- Fast charge and normal charge and wireless charge;
- Large scale charge and discharge;
- Unapproved chargers e.g. over voltage or current;
- Heat issues (charging with and without the back, in a range of environments);
- Its new Iris scanner;
- Design of any other component;
- USB-C connector and up to 4000V electrostatic discharge;
- Pre-installed apps and common post installed apps (perhaps causing processor overload);
- Operating system; and
- And dozens of tests to generally abuse the 200,000 test devices and 30,000 batteries.
None of the above were found to have anything to do with the problems.
Samsung also looked at manufacturing and logistics and none of the processes including battery handling were found to have any connection to the affected phones.
Sajeev Jesudas, president, Consumer Business Unit, global safety mark testing company UL, presented its findings that concentrated on the battery construction and safety.
It found that the 3500mAh capacity in a smaller form factor was a contributing factor, but that the affected batteries had different manufacturing defects beyond what Samsung could have reasonably foreseen. “Internal short circuits, poor ultrasonic welds (sharp edge protrusion) and missing insulation tape, all in a sealed unit.”
Jesudas also stated that “The Note7 device was in no way a contributor to this issue.” (Comment: It appears that Samsung did not design the battery, but rather asked battery makers to do so – it simply wanted 3500mAh in a certain package size.)
Dr Kevin White, principal scientist, Exponent, looked at the whole energy ecosystem, battery, chargers, the commonly used pouch cell, jelly-roll construction and more.
It found that in the battery A case, the pouch cell outer casing did not provide enough room to prevent corner deflection increasing its chance of fire if mishandled. In the case of battery C, it found that manufacturing defects on poorly controlled ultrasonic tab welds contributed to puncturing the sheet and allowed the anode and cathode to touch.
Dr White concluded that battery management software, electronic components, chargers, travel adaptors, wireless charge and more in the energy ecosystem did not contribute to the failure and were above acceptable specification. “The circuits in the Note7 could defend against all abuse except major battery manufacturing defects.”
Holger Kunz, executive vice-president, Products, TUV Rheinland AG, was charged with investigating logistics and manufacturing to see if it contributed in any way.
It tested the assembly, transit, warehousing and logistics and concluded that no work processes showed any weakness or contribution. Kunz took some responsibility for the time taken to test and come up with definitive results – TUV had by far the most geographically diverse task.
What Samsung is doing
The recall is what can only be described as a comedy of errors. One could speculate that Samsung could have taken more care to ensure the battery A issues did not occur again. But batteries are sealed units and, until now, component purchasers relied on manufacturers to have approved QA processes to produce identical items to specification.
Nevertheless, Samsung missed this, whether in its haste to recall phones or in its component supply line processes.
It has implemented multi-layer safety measures for all its battery-powered devices including more involvement in the design and safety standards for materials used. It will be incorporating solid brackets around all batteries to add deflection protection and changing its software algorithms to better detect anomalies during charging – temperature, current, and duration.
It is adding QA safety teams to focus on each major component and ensure manufacturer compliance with its specifications. Samsung has implemented its own eight-point check outside the battery makers' QA, including increased sample destruction, X-ray, random disassembly, simulated two weeks’ continuous use, and handling matters.
It has established a Battery Advisory Group comprising four noted experts and academics to advise on battery safety and innovation including:
- Clare Grey, Ph.D., Professor of Chemistry, University of Cambridge.
- Gerbrand Ceder, Ph.D., Professor of Materials Science and Engineering, UC Berkeley.
- Yi Cui, Ph.D., Professor of Materials Science and Engineering, Stanford University.
- Toru Amazutsumi, Ph.D., CEO, Amaz Techno-consultant.
Members of the group commented individually and the general thrust is that the scale of the investigation is unprecedented and the root-cause analysis will have a major impact beyond Samsung that has agreed to make the methodology and findings available to the industry.
I have stuck to what was said in the official report and presentation. There were the inevitable references by D.J. Koh to regaining trust, and about Samsung's commitment to quality and innovation, but we all expect that from Samsung as we do from any premium designer and manufacturer.
I am convinced that Samsung acted diligently, responsibly and quickly, not only in the two recalls that recovered about 96% of the handsets (about double the average) but in doing this regardless of any cost or reputational damage. In my opinion, no other company has ever acted as quickly or transparently in such a huge recall.
In talking later with senior Samsung Australian representatives, journalists learned that 75% of the Australian recalls opted for a Samsung GS7/Edge replacement, 15% sought a refund and indicated they would wait for a new S Pen device, and the remaining 10% indicated they would buy another brand. Samsung’s market share worldwide has remained relatively stable.
Unfortunately, none had any information on future Note or S Pen devices nor if Samsung might revert to removable batteries.
The issue is a lesson to all and we are damned lucky that there have not been more lithium-ion fires in many more devices – remember hoverboards in 2015?