Samsung recall: Tech solutions to enhance lithium-ion battery safety | EDN

http://www.edn.com/design/power-management/4442706/Samsung-recall–Some-possible-tech-solutions-to-enhance-lithium-ion-battery-safety-

Exploding lithiun batteries are in headlines every now and then. How they can be made safer?

134 Comments

  1. Tomi Engdahl says:

    Making sense of complex global lithium-ion battery regulations
    http://www.edn.com/design/power-management/4458542/Making-sense-of-complex-global-lithium-ion-battery-regulations

    Unfortunately, lithium batteries have made major headlines in past two decades regarding safety. Many of these incidents have caused billions of dollars in brand and property damage. Some incidents have also caused deaths and severe injuries. Some of the most notable incidents include the following:

    UPS Cargo Airline Flight 6 crashed and killed both pilots in 2010; the root cause was traced to lithium-ion batteries in the cargo hold.
    Sony batteries used primarily in Dell laptops started catching fire in 2006; the root cause was traced to bad impurities within the cell causing a short (over 9 million batteries were recalled)
    Boeing Dreamliners were grounded due to battery fires in 2013; the root cause was an internal short in the cell (over $600 million of damage for Boeing)
    Samsung Note 7 batteries started catching fire in 2016; multiple root causes traced to cell manufacturing and multiple injuries reported. Samsung took a loss of over $5 billion due to the recall.

    These examples just highlight some of the incidents with lithium-ion batteries and the potential damage it could do. Due to its volatile nature, many organizations/countries have put regulations in place to ensure the batteries they are getting are safe. We will look into which battery regulations your battery may need and what they entail.

    Which regulations do you need?

    In order to determine which regulations your rechargeable lithium ion battery solution may need, you need to ask yourself some questions. Are you going be shipping batteries by themselves? 99% of the time, the answer will be yes. And if yes, then you will need to perform UN 38.3 testing (see transportation regulations section.) Next, are you going to be shipping battery products into Europe (EU)? If yes, then you will need to do IEC 62133 (see international regulations). Is your battery going to be used in a device that complies to a UL end device spec that calls for the battery to be UL certified? If yes, then you will need to do UL2054 (see US safety regulations). Is your battery going to be shipped to China, Russia, Thailand, India, Korea, or Japan? If yes, then additional testing is needed and is specific to the country (see other regulations).

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  2. Tomi Engdahl says:

    Samsung recall analysis: form factors and battery reliability
    http://www.edn.com/electronics-blogs/brians-brain/4458618/Samsung-recall-analysis–form-factors-and-battery-reliability

    Back in early January, EDN published my missive about the recent battery failure-induced recall of Samsung’s just-introduced Galaxy Note 7 “phablet.” At the time, the root cause(s) of the thermal runaway-categorized battery breakdowns had not yet been officially announced, but later that same month, Samsung revealed the results of its in-depth laboratory tests, which were eventually able to replicate field failures.

    As mentioned in my earlier writeup, Samsung initially used two different battery suppliers for the Galaxy Note 7, its own Samsung SDI subsidiary, along with an independent company called ATL.

    The two different batteries, according to Samsung, had two different associated failure mechanisms.

    For the first battery, Samsung says a design flaw in the upper right corner of the battery made the electrodes prone to bend and, in some cases, led to a breakdown in the separation between positive and negative tabs, causing a short circuit.

    Samsung believes there was nothing wrong with the design itself, but says a manufacturing issue led to a welding defect that prompted that battery to also short circuit and ignite.

    “We believe if not for that manufacturing issue on the ramp [of battery B], the Note 7 would still be on the market,” Samsung Electronics America head Tim Baxter told Recode.

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  3. Tomi Engdahl says:

    Samsung’s new eight-step battery safety check includes: durability testing, visual inspection, X-rays, charge and discharge tests, tests of total volatile organic compounds (TVOC), disassembling tests, accelerated usage tests, and open circuit voltage tests.

    Source: http://www.edn.com/electronics-blogs/brians-brain/4458618/Samsung-recall-analysis–form-factors-and-battery-reliability

    Reply
  4. Tomi Engdahl says:

    Chaim Gartenberg / The Verge:
    iFixit teardown confirms Note 7 Fan Edition is just a Note 7 with a new, smaller battery — Like a phoenix from the ashes, Samsung’s ill-fated Galaxy Note 7 has emerged from the fires of its battery woes reborn as the Samsung Galaxy Note 7 Fan Edition, a refurbished Note 7 that, hopefully, won’t explode.

    iFixit teardown confirms Note 7 Fan Edition is just a Note 7 with a new, smaller battery
    https://www.theverge.com/circuitbreaker/2017/7/13/15967474/samsung-galaxy-note-7-fan-edition-ifixit-teardown-smaller-battery

    Like a phoenix from the ashes, Samsung’s ill-fated Galaxy Note 7 has emerged from the fires of its battery woes reborn as the Samsung Galaxy Note 7 Fan Edition, a refurbished Note 7 that, hopefully, won’t explode. Samsung announced that it’d be using some original Galaxy Note 7 parts in the Fan Edition back when it was first announced, but it was unclear what that balance would be between old and new parts.

    Fortunately, iFixit has performed its traditional teardown of the resurrected phablet and confirmed that the answer to the question of “how much of Fan Edition is the same as an original Note 7?” is “Virtually all of it.” The biggest difference is perhaps the most crucial, though: the Fan Edition has a battery that’s roughly 9 percent smaller, offering 12.32 Wh of charge to the original Note 7’s 13.48 Wh battery.

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  5. Tomi Engdahl says:

    Freezing Plus Phase Change May Yield Safer, Flexible Lithium Batteries
    http://www.powerelectronics.com/batteries/freezing-plus-phase-change-may-yield-safer-flexible-lithium-batteries?NL=ED-003&Issue=ED-003_20170814_ED-003_790&sfvc4enews=42&cl=article_2_b&utm_rid=CPG05000002750211&utm_campaign=12477&utm_medium=email&elq2=b814c260429342f7b2d1c16c6db3afef

    The dangers associated with lithium-based batteries are well-known to designers. Any inconsistencies in the manufacturing process, mismanagement during charging/discharging cycles, or improperly managed thermal issues can cause fire and even explosion. It comes as no surprise, then, that the search for a safer way to build these high-density, lightweight, electrochemical energy-storage components has attracted significant attention.

    A four-person team at Columbia University’s Fu Foundation School of Engineering and Applied Science developed a technique that may offer a viable approach to a better electrolyte and, by extension, batteries.1,2 By controlling the structure of the solid lithium electrolyte, they developed a solid electrolyte that’s safer, non-flammable, and non-toxic, thus avoiding the concerns associated with liquid electrolytes.

    Creation of the electrolyte is based on lithium-aluminum-titanium-phosphate Li1+xAlxTi2-x(PO4)3 nanoparticles (LATP NPs), which are processed with other chemicals to form a ceramic precipitate.

    A new “ice templating” technique allows formation of a solid, ceramic-based, polymer lithium electrolyte for batteries with straight channels for improved conductivity, energy density, and flexibility.

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  6. Tomi Engdahl says:

    Samsung Galaxy Note 4 Batteries Are Being Recalled For Overheating Risk
    https://hardware.slashdot.org/story/17/08/16/2010201/samsung-galaxy-note-4-batteries-are-being-recalled-for-overheating-risk

    According to The Verge, over 10,000 batteries for the Galaxy Note 4 are being recalled for risk of overheating that could lead to burns or fires. Given last year’s Note 7 fiasco, this recall sure doesn’t sound good. It is, however, far more limited than the Note 7 recall and doesn’t appear to be Samsung’s fault.

    “FedEx Supply Chain is conducting this recall of non-genuine Samsung batteries as some of them are counterfeit,” the spokesperson said.

    Galaxy Note 4 batteries are being recalled for overheating risk
    https://www.theverge.com/2017/8/16/16156934/galaxy-note-4-battery-recall-att-fedex

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  7. Tomi Engdahl says:

    Keeping it safe: The lithium-ion battery
    http://www.edn.com/design/power-management/4458808/Keeping-it-safe–The-lithium-ion-battery

    As lithium ion batteries are becoming more and more prevalent in all of our electronics, there is a lot of circuitry that is keeping them from exploding. This article will pick-up from the introductory article, Making sense of complex global lithium-ion battery regulations, and go into detail of how the circuitry works inside a lithium-ion battery to keep it safe. We will discuss the numerous protection architectures out there and pros and cons of it.

    Electronics

    Although lithium-ion chemistry has many advantages over other cell chemistries, the biggest drawback is its safety performance. A lithium-ion cell can create a thermal event if not used properly. Robust electronics and fusing needs to be incorporated in the battery design to ensure that it is being operated within safe operating conditions.

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  8. Tomi Engdahl says:

    The Science Behind Lithium Cell Characteristics and Safety
    https://hackaday.com/2017/09/18/the-science-behind-lithium-cell-characteristics-and-safety/

    To describe the constraints on developing consumer battery technology as ‘challenging’ is an enormous understatement. The ideal rechargeable battery has conflicting properties – it has to store large amounts of energy, safely release or absorb large amounts of it on demand, and must be unable to release that energy upon failure. It also has to be cheap, nontoxic, lightweight, and scalable.

    As a result, consumer battery technologies represent a compromise between competing goals. Modern rechargeable lithium batteries are no exception, although overall they are a marvel of engineering. Mobile technology would not be anywhere near as good as it is today without them. We’re not saying you cannot have cellphones based on lead-acid batteries (in fact the Motorola 2600 ‘Bag Phone’ was one), but you had better have large pockets. Also a stout belt or… some type of harness? It turns out lead is heavy.

    Rechargeable lithium cells have evolved tremendously over the years since their commercial release in 1991.

    two approaches, lithium-ion (Li-ion) and lithium-polymer (Li-Po) cells were developed

    Despite a large number of chemistries, lithium batters still have several parameters in common that are very relevant to using them safely and effectively in our projects.

    C-rate: This determines how quickly you can draw or store current. It is a simple multiplier – a cell with a C-rate of 2 can tolerate a discharge rate twice of that listed as the capacity. For example, in a 200 mAh cell, this means you could safely draw up to 400 mA.

    It’s worth noting that the C-rate to charge lithium cells is typically significantly lower than the discharging rate (although it depends on the exact chemistry used, some are much faster than others).

    Undervoltage: We’re told not to let the voltage of lithium cells drop below a given voltage (varies by cell type but often around 3 volts). This is unfortunate because we’re often ‘gifted’ dead lithium cells registering a low voltage that would be nice to use again, for example in a new flashlight. Even though they may charge again, it’s not a good idea to do so.

    It turns out that copper foil is generally used in the cells as a current collector. When the voltage drops below a certain threshold, some of the copper in the negative electrode starts to dissolve and migrate. When you then recharge the cell in question, it forms dendrites of elemental copper somewhere they shouldn’t be.

    Some (but not all) types of lithium cell have a built-in circuit that permanently disables the cell if the voltage drops too low, as a consumer safety feature. Cylindrical lithium cells such as the 18650 are more likely to contain this type of circuit than pouch cells.

    Overvoltage: Cells can also be damaged if charged to too high a voltage. The reactions that occur depend on the exact cell chemistry, but a common one is the plating of solid lithium metal on the negative electrode, resulting in a permanent loss of capacity. Lithium metal is extremely reactive and can react with the electrode and electrolyte to release heat and gas, potentially leading to a fire.

    Another common reaction is the decomposition of the electrolyte. The electrolyte is typically an organic solvent containing lithium salts, so can be electrolyzed

    The gas pressure can cause mechanical failure of the cell, and the solids can form block pores on the electrodes, reducing their capacity.

    Thermal runaway: Certain undesirable chemical reactions in a cell both generate heat, and occur faster at higher temperatures. Whether this leads to a fire or just a dead cell is an interaction of several factors, typically cell temperature, physical damage, and charge state

    Manufacturing defects: With the number of things that can go wrong with lithium cells, quality control is critical.

    Swelling of lithium cells: Abusing lithium cells as above can definitely cause swelling, especially in pouch cells. However, even if you use them correctly, a few cells will puff up for reasons that are poorly understood.

    Here, the main danger is that the pouch cell is punctured by something nearby. The pressure caused by a swelling lithium cell can also crack screens and warp keyboards.

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  9. Tomi Engdahl says:

    DIY LiPo Protectors
    https://hackaday.com/2017/09/25/diy-lipo-protectors/

    Spiderman’s Uncle Ben was known to say, “With great power comes great responsibility.” The same holds true for battery power. [Andreas] wanted to use protected 18650 cells, but didn’t want to buy them off the shelf. He found a forty cent solution. Not only can you see it in the video, below, but he also explains and demonstrates what the circuit is doing and why.

    Protection is important with LiPo technology. Sure, LiPo cells have changed the way we use portable electronics, but they can be dangerous. If you overcharge them or allow them to go completely dead and then charge them, they can catch fire. Because they have a low source resistance — something that is usually desirable — short-circuiting them can also create a fire hazard. We’ve covered the chemistry in depth, but to prevent all the badness you’ll want a charger circuit.

    The little circuit fits on top of a standard 18650 cell and uses two chips (one of which is just a dual MOSFET) and three discrete components. It does add about 3 mm to the cell. [Andreas] found that battery holders with a coiled spring would accommodate the extra length, but those with metal leaf springs would not.

    #160 40 Cent Do-It-Yourself Li-Ion Protectors for 18650 Cells (Tutorial) and how they work
    https://www.youtube.com/watch?v=1rg3ZWxBNUE

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  10. Tomi Engdahl says:

    iPhone 8 Plus Battery Bursts While Charging, Destroys Case and Screen
    The batteries are made by ATL, the Galaxy Note 7 supplier
    http://news.softpedia.com/news/iphone-8-plus-battery-bursts-while-charging-destroys-case-and-screen-517860.shtml

    An iPhone 8 Plus 64GB has reportedly burst in Taiwan while it was being charged, raising questions about Apple’s battery provider ATL, which also made the famous exploding Samsung Galaxy Note 7 batteries.

    Ever since the Samsung Galaxy Note 7 started catching fire, everyone is now looking for this problem with each new device release. In Samsung’s case, it was a production mistake that cost the company a lot and forced them to retire an entire line of devices.

    Apple hasn’t been spared, but the number of exploding iPhones was much lower if we take into account the total of units sold by the company. Now, their latest iPhone 8 and iPhone 8 Plus have started to ship to customers, and some problems have already begun to appear.

    “Battery destroys the shell and pushes out the screen”

    While it’s not as exciting as catching fire, the fact that a woman’s iPhone 8 Plus 64GB had the screen pushed out by an inflating battery is bad enough

    Furthermore, it’s been reported that she was using the official charger and that she wasn’t a heavy user

    “The battery maker is under scrutiny again”

    The company that makes the batteries for the latest iPhone 8 and iPhone 8 Plus is called ATL. It might sound familiar because it’s the same one that provided the batteries for Samsung Galaxy Note 7, and we all know how well that went.

    In fact, Samsung ditched the ATL battery supplier after they failed to confirm the new regulations imposed. Because they were unable to guarantee the safety of the cells in a way that satisfied Samsung, ATL was dropped as a supplier.

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  11. Tomi Engdahl says:

    Prevent Overcharging of Li-Ion Cells
    http://www.electronicdesign.com/test-measurement/prevent-overcharging-li-ion-cells?NL=ED-003&Issue=ED-003_20171018_ED-003_184&sfvc4enews=42&cl=article_1_b&utm_rid=CPG05000002750211&utm_campaign=13624&utm_medium=email&elq2=c97e193fb6c841159a02a74912e573aa

    Four-wire remote sensing is generally the best solution, which requires the use of multiple probes. Thus, your system should include probe-check functions to guard against failure.

    Over the years, serious concerns have emerged about lithium-ion cell safety. There have been factory fires, mobile phones and laptop computers bursting into flames, and even the grounding of a 787 aircraft. So, when forming or charging Li-ion cells in manufacturing or during characterization in R&D, special attention must be paid to prevent dangerous conditions that can lead to those cell fires.

    One key area of concern is applying overvoltage or overcharging during charging. If the charging voltage is increased beyond the recommended upper cell voltage or if the cell is overcharged, lithium ions can build up on the anode as metallic lithium, which is called lithium plating. The plating can occur as dendrites inside the cell, which could ultimately result in a short circuit between the electrodes. The short circuit can increase the internal cell temperature, which may lead to thermal runaway that results in damaged cells and possibly fire.

    To maintain the highest voltage-regulation accuracy and control when large current is flowing into/out of the cell, it’s best to use a four-wire system called remote sensing. By remote sensing, the cell-charging electronics can adjust output voltage to compensate for the voltage drop in the power leads, even as the current changes.

    Remote Sensing Prevents Overvoltage, But…

    Remote sensing with a four-wire connection ensures the voltage on the cell will be maintained carefully, as the sense wires provide a voltage-regulation feedback system to the charger that permits the charger to regulate voltage accurately. Thus, no overvoltage can be applied and there’s no overcharging. Remote sensing also means four probes will be in contact with the cell. This raises the concern about probe failures, as more probes and associated wires mean more possible failures.

    Solution: Probe Check

    While a four-wire system has exceptional benefits, using more probes means that there’s greater potential for probe failure. As a result, a well-designed charger will include probe-check functions. The application of overvoltage is the most hazardous condition, since it can lead to fire, so the most basic level of probe check should detect sense probe failures.

    A simple method to implement a sense probe check is to detect if there’s a difference between the voltage measured on the sense lines and the voltage on the power lines. This difference will occur upon failure of a sense probe.

    Beyond this basic probe-check method, other more advanced and sophisticated methods can be deployed. One more advanced probe check involves sensing the resistance of the probes and even automatically detecting which of the four probes has failed. Of course, adding more sophistication to the charger increases the cost and complexity.

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  12. Tomi Engdahl says:

    Laptop Flipflop: Now U.S. Tries To Ban Laptops In Checked, Not Carry-On, Luggage
    https://www.forbes.com/sites/martinrivers/2017/10/21/laptop-flipflop-now-u-s-tries-to-ban-laptops-in-checked-not-carry-on-luggage/2/#1b63c2c5245f

    Seven months after America banned laptops from the passenger cabins of flights from the Arab World – forcing travelers to check them into cargo holds – the Federal Aviation Administration (FAA) wants global airlines to ban the very practice its government had previously imposed on them.

    The FAA’s advice is based on new safety tests showing that the rechargeable lithium-ion batteries found in laptops could bring down an aircraft if they overheat when packed next to flammable items in checked luggage.

    ts findings are published in a paper submitted to the International Civil Aviation Organization (ICAO), the UN agency that issues non-binding air safety guidance to the international community. The proposed ban has already won the backing of the European Aviation Safety Agency (EASA) and Airbus, the European aircraft manufacturer, establishing a consensus that ICAO is unlikely to overrule. Even after it weighs in, though, individual governments will retain the final say on ratifying any measures.

    The report cites ten experiments the FAA conducted with fully-charged laptops packed inside a suitcase.

    For the first four tests, the bag contained no other hazardous items and the resultant fires were extinguished by the Halon fire-suppression system that is widely used in cargo holds. In a fifth experiment without other hazardous items, the Halon system was not present and the suitcase was fully consumed by fire.

    But it was the subsequent tests that were most alarming, as they demonstrated how certain everyday items can exacerbate thermal runway to such a degree that the lifesaving Halon system becomes ineffective.

    Other experiments showed that nail polish remover, hand sanitizer and rubbing alcohol also accelerate battery fires, but it was the explosive effect of the aerosol can that had experts most concerned.

    While an exploding aerosol can is unlikely to cause structural damage to an aircraft, the impairment of the Halon system means that a fire could spread freely through the cargo hold and into other compartments such as the passenger cabin and electronics bay. This chain of events, the FAA warns, “could lead to the loss of the aircraft”.

    One reason that such an incident has not yet occurred, it suggests, is that passengers are “not typically placing their [laptops] in checked baggage”

    The FAA has repeatedly warned about the dangers of lithium-ion batteries and devices that use them, specifically banning spare batteries and e-cigarettes from checked luggage. Other battery-powered devices such as hover-boards and certain cell-phones have also been subject to FAA edicts.

    When did laptops become such a danger on planes?
    http://mashable.com/2017/05/12/laptop-ban-airline-europe-trump/#im3DkzrefOqu

    First shoes, then liquids, and now laptops.

    With reports suggesting the airplane cabin laptop ban may soon expand from flights originating in eight Middle Eastern and African countries to parts of Europe, it’s clear that our computers have now joined the list of things we have to worry about when flying.

    However, some big questions remain: Why now, and why are laptops considered OK in a plane’s cargo hold but not in its cabin?

    CNN reported in March that an unspecified al Qaeda affiliate was in fact working to disguise explosives as laptop components. As such, we know that the initial laptop ban wasn’t totally out of the blue.

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  13. Tomi Engdahl says:

    Lithium Ion Versus LiPoly In An Aeronautical Context
    https://hackaday.com/2017/10/23/lithium-ion-versus-lipoly-in-an-aeronautical-context/

    When it comes to lithium batteries, you basically have two types. LiPoly batteries usually come in pouches wrapped in heat shrink, whereas lithium ion cells are best represented by the ubiquitous cylindrical 18650 cells. Are there exceptions? Yes. Is that nomenclature technically correct? No, LiPoly cells are technically, ‘lithium ion polymer cells’, but we’ll just ignore the ‘ion’ in that name for now.

    Lithium ion cells are found in millions of ground-based modes of transportation, and LiPoly cells are the standard for drones and RC aircraft. [Tom Stanton] wondered why that was, so he decided to test the energy density per mass of these battery chemistries, and what he found was very interesting.

    Lithium ion plane battery
    https://www.youtube.com/watch?v=UB8fas6zBSE&t=601s

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  14. Tomi Engdahl says:

    These Explosions Show Why the FAA Doesn’t Want Laptops in Luggage
    https://www.wired.com/story/these-explosions-show-why-the-faa-doesnt-want-laptops-in-luggage/

    Stop me if you’ve heard this one before. The US government wants a “laptop ban” on planes.

    But this time, it’s to prevent fliers from putting large electronics, like laptops, into their checked luggage. This seems like an about-face. Earlier this year, a chaotically implemented ban did the exact opposite, demanding passengers on flights from certain Middle Eastern and African countries pack tablets, DVD players, and laptops into their suitcases, to travel in the belly of the plane. Department of Homeland Security officials worried terrorists would disguise bombs as batteries inside these larger electronic gizmos.

    The department lifted that laptop ban in June, announcing more rigorous security screening instead. But the temporary increase in large electronics in the hold left the Federal Aviation Administration, which oversees America’s flying industry, with some questions: Is it safe to stow electronics—especially those with lithium-ion batteries—in cargo holds?

    It was time for the FAA to blow some stuff up. You know—science. The agency ran a series of experiments, placing laptops inside typical suitcases next to your standard flammable toiletries: nail polish remover, hand sanitizer, and most explosively, an aerosol can of dry shampoo.

    n separate tests, the FAA also experimented with a galley cart, which airlines might use to store large numbers of in-flight-entertainment tablets together. If a device there catches fire and spreads, the resulting bang is dramatic, and potentially deadly.

    The FAA’s recommended ban is being debated by a Dangerous Goods Panel at an International Civil Aviation Organization meeting in Montreal, Canada, this week. If there’s agreement, ICAO, which is part of the UN, could adopt the ban, which will likely be announced in January 2018 and implemented a year later.

    In summation: A ban may have lead to an opposite ban. But safety comes first.

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  15. Tomi Engdahl says:

    Current Sensing in Lithium-ion Energy Storage Systems
    For the highest accuracy, opt for a simple architectur
    http://www.powerelectronics.com/power-management/current-sensing-lithium-ion-energy-storage-systems?NL=ED-003&Issue=ED-003_20171120_ED-003_847&sfvc4enews=42&cl=article_1_b&utm_rid=CPG05000002750211&utm_campaign=14166&utm_medium=email&elq2=00148c1342614baaaebccec5b924cab5

    Current sensing has long been an important function implemented by battery management systems (BMS), modules which monitor and protect high-capacity batteries. In both lithium-ion and sealed lead-acid battery types, current measurements are used to protect the battery against abuse and ensure its safe use by providing for emergency shut-down in over-current conditions. For protection and safety functions alone, the accuracy of the current measurements can be at a fairly low level. The system designer may specify the over-current conditions conservatively, so that even if the current sensor severely underestimates the current, the safe shut-down threshold is not crossed.

    Now, however, the requirements for current sensing are becoming much more stringent in certain applications. Car manufacturers in particular are working furiously to improve the performance and consumer appeal of electric vehicles (EVs). Range anxiety is one of the biggest impediments to consumer adoption of EVs, and so the accuracy of an EV’s “fuel gauge”—that is the State of Charge (SOC) reading showing how much energy is available for use—is of critical importance to the driver. Accurate SOC measurements also enable the BMS to optimize operation for long cycle life, in EVs and in industrial equipment, by maintaining the SOC at between 0% and 80%.

    The accuracy of the fuel gauge depends absolutely on the accuracy of the BMS’s current measurements. And as this article will show, precision analogue circuitry and an appropriate architecture can provide much higher levels of accuracy than are commonly achieved in today’s BMS.

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  16. Tomi Engdahl says:

    Lithium-ion Overcomes Limitations
    New battery protection for portable electronics cuts manufacturing steps and costs.
    http://www.powerelectronics.com/power-management/lithium-ion-overcomes-limitations?NL=ED-003&Issue=ED-003_20171227_ED-003_367&sfvc4enews=42&cl=article_2_b&utm_rid=CPG05000002750211&utm_campaign=14677&utm_medium=email&elq2=72e3ff46d91e4b419f09b75c823aa89e

    Transparency Market Research analysts predict that the global lithium-ion battery market is poised to rise from $29.67 billion in 2015 to $77.42 billion in 2024 with a compound annual growth rate of 11.6 % (Fig. 1). They note that growth has already spread from the now ubiquitous consumer electronics segment to automotive, grid energy, and industrial applications. While billions of dollars are continuing to be invested in the search for safer, longer lasting and higher energy density batteries, it is difficult to see lithium-ion based batteries being replaced anytime soon.

    One of the primary limitations of the lithium-ion battery is the need for protection circuits to maintain the voltage and current within safe limits. These batteries need to be well protected against overcurrent and overtemperature threats. In addition, battery suppliers continue to look for ways to streamline manufacturing to keep their costs low in such a competitive environment.

    This article will present the primary issues involved in designing overcurrent and overvoltage protection for lithium-ion batteries. It will also introduce a new series of overcurrent and overtemperature devices that match the expanding needs of today’s smaller electronic designs, and also give battery suppliers a way to cut manufacturing steps and costs.

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  17. Tomi Engdahl says:

    Why You Shouldn’t Charge Your Mobile Phone Overnight
    http://time.com/4949569/mobile-phone-charge-overnight/

    You may already have heard the warnings: Don’t overcharge your mobile phone. Make sure you unplug it from the charger after it reaches 100%. Don’t leave it charging overnight. Or else.

    The direness implicit in those imperatives may be overblown, but they’re not paranoid conspiracy dictums — you still shouldn’t overcharge your phone. Here’s why.

    First, the good news. You can’t overcharge your phone’s battery, so don’t worry about that. Your phone stops drawing current from the charger once it reaches 100%, according to Cadex Electronics marketing communications manager John Bradshaw. Cadex manufactures battery charging equipment. “Go ahead and charge to 100%,” Bradshaw says. “No need to worry about overcharging as modern devices will terminate the charge correctly at the appropriate voltage.”

    “Modern smart phones are smart, meaning that they have built in protection chips that will safeguard the phone from taking in more charge than what it should,”

    Whew, that’s a relief. Okay, what’s the not-so-good news?

    Even though a charger turns off the juice when your phone reaches 100%, the charger will continue to top off the charge during the night, says Bradshaw. Such a “trickle charge” attempts to keep it at 100% to compensate for the small bit of charge that your phone just naturally loses on its own. So your phone is constantly being bounced between a full charge and a bit below a full charge. These trickle charges can lead to higher ambient temperatures for your phone, which can reduce capacity over time.

    “Li-ion does not need to be fully charged as is the case with lead acid, nor is it desirable to do so,” according to an article from Cadex’s Battery University site. “In fact, it is better not to fully charge because a high voltage stresses the battery.”

    Rechargeable batteries are also basically doomed from the start. Batteries in mobile devices are in constant decay from the moment they’re first used, says Campos. This results in a gradual loss of their capacity, or ability to hold a charge. That’s why those who’ve owned a phone more than a couple of years tend to find that their battery loses its charge quicker than just after purchase.

    By keeping your phone charged overnight, you’re actually increasing the amount of time your device spends with the charger, thereby degrading its capacity that much sooner.

    “If you think about it, charging your phone while you’re sleeping results in the phone being on the charger for 3-4 months a year,”

    Don’t wait until your phone gets close to a 0% battery charge until you recharge it, advises Cadex’s Bradshaw. Full discharges wear out the battery sooner than do partial discharges. Bradshaw recommends that you wait until your phone gets down to around a 35% or 40% charge and then plug it into a charger. That will help preserve the capacity of the battery.

    Reply
  18. Tomi Engdahl says:

    A Smart Home Needs Smart Battery Management
    http://www.electronicdesign.com/power/smart-home-needs-smart-battery-management?code=UM_NN6TI100&utm_rid=CPG05000002750211&utm_campaign=14954&utm_medium=email&elq2=2550c63dd33c4a51ab4efdd7607104a8

    No doubt about it—the world is getting smarter. Widely available wireless connectivity, low-cost sensors, and low-power embedded microcontrollers have spawned numerous “smart” consumer products, including phones, watches, and credit cards. Behind the scenes, we’re seeing the rise of the smart factory and the smart grid, and researchers are even working on smart dust.

    Powering the Smart Home

    Connecting many devices opens up a host of intriguing possibilities, but providing power to such a disparate collection of products poses problems for the system designer, particularly in a home that wasn’t designed to accommodate a “smart” installation.

    There are two basic classes of home-automation applications for batteries:

    The battery provides the primary source of power. These include the remotely located peripherals mentioned above, mobile devices such as cleaning robots, and wearables like in-home medical monitors.

    The battery performs a secondary role. It acts as a backup and comes online if a primary ac-powered source fails. Continuity of power is critical for home security and fire protection, of course, but it’s also important for emerging home applications such as patient monitoring and senior care. Energy storage systems, and backup supplies for telematics, UPS, and servers, have similar use cases.

    Those looking to reduce maintenance and replacement costs are turning more to rechargeable lithium-ion (Li-ion) batteries for both types of applications. Suppliers of power integrated circuits (ICs) have developed a wide range of power-management and charging solutions for battery-powered devices.

    The key functions of a battery-management system include managing the charging cycle to minimize the charging time without stressing the battery and reducing its useful life; monitoring the current state of the battery; detecting and reporting fault conditions; and taking appropriate action.

    Reply
  19. Tomi Engdahl says:

    EEVblog #919 – How To Charge Li-Ion/LiPo Batteries With A Power Supply
    https://www.youtube.com/watch?v=jNmlxBXEqW0

    How to safely charge Lithium Ion & Lithium Polymer batteries with a bench power supply, for when you don’t have the correct charger available.
    WARNING:
    Take care using PSU’s for charging unprotected cells. A fault in the PSU might overload or short the battery & that could be dangerous.
    Always watch your battery during charging using a general purpose technique like this.

    Reply
  20. Tomi Engdahl says:

    Building a Better Battery
    http://www.powerelectronics.com/batteries/building-better-battery?NL=ED-003&Issue=ED-003_20180219_ED-003_349&sfvc4enews=42&cl=article_1_b&utm_rid=CPG05000002750211&utm_campaign=15417&utm_medium=email&elq2=b808b8d0462c4b0eb6a5bb61c2bf28c6

    The race to the world’s greatest battery is on, and scientists from APL may have just won first place with the world’s first near-destructible lithium-ion battery.

    A cross-functional team of scientists from John Hopkins University Applied Physics Laboratory (APL), the University of Maryland, and the Army Research Laboratory (ARL) have invented a flexible, gel-based lithium-ion (Li-ion) battery that continues to power load even after being cut in half, submerged in water, and shot with an air cannon. The breakthrough technology is novel in its ability to withstand abuse and may redefine how the world thinks about power.

    Lithium-Ion

    Research on lithium-ion battery technology began in 1912. In 1970, the first Li-ion battery hit the market, and the technology has rapidly increased in popularity since. Li-ion production capacity was 29 gigawatt-hours in 2016. The demand for mobile power solutions for consumer electronics only continues to rise, and to date, there has not been a better rechargeable power solution than Li-ion. Li-ion technology, however, is not without issues.
    The Problem with Existing Li-ion Batteries

    Lithium-ion technology poses a serious problem: Li-ion batteries can explode and burst into flames.

    The electrolyte used in Li-ion batteries, however, is highly flammable and bursts into flames when punctured or if conditions of extremely high heat are present (say, the kind of high heat present in a flammable Samsung Galaxy smartphone).

    The new gel-based battery invented by APL researchers, however, may have solved the known issues with using Li-ion technology.

    The flexible battery developed by the team of scientists at APL, UMD, and ARL is based on a novel electrolyte that APL and UMD researchers discovered in 2015, called “water-in-salt.” The team embedded the water-in-salt electrolyte in a polyvinyl alcohol (PVA) polymer matrix. The result is a gel polymer electrolyte (GPE) that is more stable than a liquid, but also boasts flexibility and the high-energy capabilities of its commercial counterparts.

    In an experiment, the research team built a prototype using the GPE substrate, enclosed between pieces of electronically insulating heat-resistant tape. The team used the battery to power a hefty motor. Then, the researchers cut the battery, submerged it in a tank of synthetic salt water, and shot it with an air cannon. The battery continued to power load despite the extreme, abusive conditions.

    The flexible GPE-based battery seems to be about 4 inches high x 1 inch wide.

    Though similar in output to traditional Li-ion batteries, the versatility of the GPE-based technology is unparalleled by both Li-ion technology and other emerging battery technologies like Al-O batteries, solid-state batteries, and micro-batteries

    Reply
  21. Tomi Engdahl says:

    Exploding e-Cigarettes Are a Growing Danger to Public Health
    https://spectrum.ieee.org/consumer-electronics/portable-devices/exploding-ecigarettes-are-a-growing-danger-to-public-health

    Exploding cigarettes sound like a party joke, but today’s version isn’t funny at all. In fact, they are a growing danger to public health. Aside from mobile phones, no other electrical device is so commonly carried close to the body. And, like cellphones, e-cigarettes pack substantial battery power. So far, most of the safety concerns regarding this device have centered on the physiological effects of nicotine and of the other heated, aerosolized constituents of the vapor that carries nicotine into the lungs. That focus now needs to be widened to include the threat of thermal runaway in the batteries, especially the lithium-ion variety.

    In July 2017, the National Fire Data Center of the U.S. Fire Administration identified 195 separate e-cigarette incidents in the United States between January 2009 and 31 December 2016. Thirty-eight incidents resulted in third-degree burns, facial injuries, or the loss of a body part.

    An online blog asserts that at least 243 e-cigarette explosions occurred from August 2009 to April 2017, resulting in 158 personal injuries. Other explosions harmed animals or property.

    E-cigarettes, also known as “vape pens,” “e-hookahs,” “mods,” “e-pipes,” “cigalikes,” and “tank systems,” are basically just electronic nicotine-delivery systems. They were first commercialized in China in 2004, and the most recent available estimate put that country’s share of total production above 90 percent. In 2015, U.S. consumers accounted for about 43 percent of the US $8 billion world market for these devices.

    internal defects cause short circuits, which raise the temperature enough to spur on reactions that release still more heat. Ultimately, this feedback loop leads to sparking, fiery self-destruction. Significantly, this phenomenon is more likely in an e-cigarette than in a cellphone because the combination of lithium-ion batteries with a heating element increases the risk of such a reaction. A battery-management system can help with the problem, but it may not prevent catastrophic failure if poor manufacturing and quality control leave defects in the battery.

    During thermal runaway, battery temperatures can reach 900 oC and release flammable and toxic gases. Well-known examples of thermal runaway include the various battery fires that led to the worldwide grounding of the Boeing 787 Dreamliner aircraft on 16 January 2013; other notable incidents involved hoverboards and Samsung’s Galaxy Note 7 smartphone.

    Reply
  22. Tomi Engdahl says:

    FAKE BRITAIN Lithium Batteries Extract
    https://www.youtube.com/watch?v=1DFzkzMGDuQ

    Geoff Leach, from DGO contributes to the Fake Britain TV series on Lithium batteries.

    Reply
  23. Tomi Engdahl says:

    Amazon Recalls 260,000 Portable Power Banks For Fire Hazard
    https://hardware.slashdot.org/story/18/03/13/2016259/amazon-recalls-260000-portable-power-banks-for-fire-hazard

    Amazon is recalling 260,000 AmazonBasics portable power banks that can “overheat and ignite,” according to a release by the Consumer Product Safety Commission. The company has received more than 50 reports of the power banks overheating in the U.S., causing chemical burns and property damage.

    Amazon recalls 260,000 portable power banks for fire hazard
    https://www.cnbc.com/2018/03/13/amazon-power-banks-recalled-for-fire-hazard.html

    Amazon has received more than 50 reports of the power banks overheating in the U.S., causing chemical burns and property damage.
    Amazon is contacting everyone who purchased one of the affected devices.
    The recall covers six versions of the Amazon Basics portable battery.

    Reply
  24. Tomi Engdahl says:

    Moment laptop explodes while charging at Letchworth business
    http://www.thecomet.net/news/moment-laptop-explodes-while-charging-in-letchworth-1-5447963

    A Letchworth business owner has issued a warning about the “potential bombs” we have in our homes after his office was destroyed by a fire which he believes was caused by a faulty laptop battery.

    Steve Paffett – owner of Allplas – says his business could be out of action for six months after his HP laptop caught fire while left on charge, with the blaze destroying his office based off Works Road.

    The managing director of the tarpaulins and netting specialists was at home asleep when his work intruder alarm woke him.

    “To my horror I was watching a bonfire on my office desk. I thought ‘what am I going to do?’ It was awful.

    Of the damage, he said: “The ground floor is ruined, all the stock is written off – luckily none of it caught fire, but it’s just covered in smoke – the whole building is filthy and reeks.

    “I’ve already been given a small insurance payment – just enough to continue to trade – but it’s not quite the same thing as being able to get on with your day.”

    Now Steve wants to warn the public about the dangers of LiPo batteries if left on charge for a substantial amount of time.

    “Just never ever leave a laptop or phone on charge overnight, as this is the result,” Steve said.

    “If it’s on and you leave it plugged in then that’s fine, but when you switch it off remember to take it off charge – it only takes a little distraction to forget.

    To limit the risk of fires caused by laptop battery chargers, Herts Fire & Rescue Service recommends the use of CE Kite marked chargers manufactured by the reputable dealer for the device.

    Steve bought his HP Envy laptop in 2014, and had never had an issue with the charger. He only decided to leave it on charge when he unplugged it and it turned off immediately.

    Reply
  25. Tomi Engdahl says:

    https://www.is.fi/digitoday/art-2000005067732.html

    Tietokonevalmistaja HP vetää pois markkinoilta kannettavien tietokoneidensa akkuja tulipalo- ja palovammavaaran vuoksi.

    Takaisinveto koskee osaa HP-, Compaq-, HP ProBook-, HP ENVY-, Compaq Presario- ja HP Pavilion -kannettavia, joita on myyty vuoden 2013 maaliskuun ja vuoden 2016 lokakuun välillä. Myös tuona aikana ostetut vaihtoakut saattavat olla vaarallisia.

    Reply
  26. Tomi Engdahl says:

    HP Recalls Over 100,000 Laptop Batteries Due to Potential Fire and Burn Hazards
    by Anton Shilov on January 26, 2017 7:00 AM EST
    https://www.anandtech.com/show/11068/hp-recalls-over-100000-batteries

    HP has expanded its voluntary recall of batteries due to fire and burn hazards. The batteries were used for various laptops sold under the HP and Compaq brands between March 2013 and October 2016. In total, the company has recalled over 140 thousand batteries in the U.S., Canada and Mexico.

    Reply
  27. Tomi Engdahl says:

    Renesas Electronics
    Putting Safety into Li-ion Battery Packs
    https://www.intersil.com/content/dam/Intersil/whitepapers/battery-management/li-ion-battery-pack-safety.pdf?utm_source=eloqua&utm_medium=email&utm_campaign=industrial&utm_content=isl94202

    The power FET is an essential safety function in a
    battery management system
    (BMS). The main purpose of
    the power FET is to isolate the battery pack from either a load or a charger in errant conditions. This
    white
    paper discusses the detection blocks and how th
    ey
    appl
    y
    to the state of the power FETs
    to ensure safe
    operation of lit
    hium ion (Li
    -
    ion) battery packs
    .
    The power FET functional block seems
    straightforward: t
    urn on the FET when a charger or load is connected
    ;
    t
    urn off the FET if anything goes wrong. Proper functionality of the power FETs requires the designer to
    understand
    the load conditions, the battery pack limitations and
    to
    have an understanding of the functional
    block circuitry.

    Reply
  28. Tomi Engdahl says:

    Evaluate Lithium Ion Self-Discharge of Cells in a Fraction of the Time Traditionally Required
    http://innovation-destination.com/2018/03/24/evaluate-lithium-ion-self-discharge-of-cells-in-a-fraction-of-the-time-traditionally-required/?NL=ED-004&Issue=ED-004_20180403_ED-004_353&sfvc4enews=42&cl=article_1_b&utm_rid=CPG05000002750211&utm_campaign=16367&utm_medium=email&elq2=bbb608a23534444f8214eb8be4971954

    Whether you are an engineer in design or manufacturing, Li-Ion cell and battery performance testing is both a priority and a challenge for you. This is especially true for evaluating cells for self-discharge. Cells exhibiting high levels of self-discharge have higher likelihood of failure and must be sorted out and the cause identified. Unfortunately, this has traditionally been a long and tedious process to perform.

    What is a cell’s self-discharge? Self-discharge of an electrical cell is the loss of charge over time while not connected to any load. Some amount of self-discharge is a normal attribute resulting from chemical reactions taking place within the cell. Compared to other types of rechargeable cell chemistries, lithium ion cells have rather low self-discharge. On their own they may typically lose about 0.5 to 1% of their charge per month.

    For this cell by itself without any load, assuming a self-discharge of 1% per month equates to a voltage loss of about 3 to 12 mV per month, depending on its % SOC.

    Additional self-discharge can result from leakage current paths existing within the cell. Particulate contaminants and dendrite growths produce internal “micro-shorts”, creating such leakage current paths. These are not normal attributes and they can lead to catastrophic failure of the cell.

    In manufacturing, it’s critical to screen out any cells exhibiting abnormally high self-discharge as early as possible in the process.

    Traditionally self-discharge is evaluated by measuring the decrease of a cell’s open-circuit voltage (OCV) over time. While it is not challenging to measure a cell’s OCV, the challenge is that it is very time-consuming.

    An alternate means to determine a cell’s self-discharge is to instead measure its self-discharge current. When such a measurement is correctly implemented, cells exhibiting excessively high self-discharge can be identified and isolated in a small fraction of the time required by the traditional OCV approach.

    Reply
  29. Tomi Engdahl says:

    KULR Gains Exclusivity to NASA, NREL Li-ion Safety Testing Devices
    http://www.powerelectronics.com/batteries/kulr-gains-exclusivity-nasa-nrel-li-ion-safety-testing-devices?NL=ED-003&Issue=ED-003_20180405_ED-003_581&sfvc4enews=42&cl=article_1_b&utm_rid=CPG05000002750211&utm_campaign=16374&utm_medium=email&elq2=9f97506f6b2e45dc8517c012859206ac

    Under agreement with the National Renewable Energy Laboratory, KULR will make and distribute Internal Short Circuit devices that reliably instigate lithium-ion cell failures.

    KULR Technology announced it has reached agreement with the National Renewable Energy Laboratory (NREL), funded by the U.S. Department of Energy, to be the exclusive manufacturing and distribution partner for the patented Internal Short Circuit (ISC) device. The ISC causes predictable battery cell failures in lithium-ion batteries, making them easier to study and, therefore, safer. KULR will begin shipping the ISC and ISC trigger cells in October 2018.

    The ISC is in response to what is probably the most dangerous lithium-ion battery failure: thermal runaway propagation. This occurs when the extreme heat and fire from the failure of a single battery cell spreads to neighboring cells, causing a chain-reaction fire and explosion

    Lithium-ion battery (Li-B) 18650 cells have a slight chance of spontaneously shorting, which heats the interior gradually to 130°C where the “separator” film melts. This triggers an explosive release of electric energy where the end cap ruptures. Subsequently, a flare emerges briefly (~1 sec); then the cell materials combust for up to one minute, releasing heat and driving the cell T > 500°C. Neighboring cells can also be heated above the critical 130°C, potentially causing them to short with the same consequences, resulting in thermal runaway. An effective passive solution is needed that works for a variety of batteries ranging in size from 10 to 4,000 cells.

    KULR’s thermal runaway shield (TRS) prevents thermal runaway in neighboring cells by keeping the temperature below 100°C. When thermal runaway occurs in a single cell, the TRS absorbs the heat and prevents adjacent cells from getting too hot and subsequently entering thermal runaway. The system is lightweight, cost-effective, and contains a flame arrestor to block the fire from reaching surrounding cells.

    “Most often, to induce an on-demand thermal runaway response in trigger cells, safety verification required over-testing, resulting in over-designing the battery,” said Dr. Eric Darcy, Battery Systems Technical Discipline Lead at NASA-Johnson Space Center. “With the ISC, researchers can now design and produce cells and cell configurations that deal with the thermal runaway threat directly.”

    Reply
  30. Tomi Engdahl says:

    Six Lithium-ion Battery Chemistries: Not all Batteries are Created Equal
    http://www.powerelectronics.com/alternative-energy/six-lithium-ion-battery-chemistries-not-all-batteries-are-created-equal?NL=ED-003&Issue=ED-003_20180427_ED-003_772&sfvc4enews=42&cl=article_1_b&utm_rid=CPG05000002750211&utm_campaign=16956&utm_medium=email&elq2=9fa5daaa0f094798b3107f894ffed8d8

    Like all technology, the lithium-ion battery has evolved over few decades, incorporating new chemistries for different applications and increased performance.

    In the most widely used in Li-ion technology (for mobile devices) for example, the positive electrode is made of lithium-iron phosphate (LiFePO4), the negative is typically made of carbon (graphite), and the electrolyte is usually comprised of lithium salt in an organic solvent.

    Like all technology, the lithium-ion battery has evolved over few decades, incorporating new chemistries for different applications and increased performance. In this roundup, we will look at some of the latest chemistries and compositions that have been developed for lithium-ion batteries and their applications.

    Reply
  31. Tomi Engdahl says:

    Apple Sued Your Combustible Phone Took Down an Airplane!!!
    http://www.tmz.com/2018/05/11/apple-sued-egyptair-flight-804-crash-phone-fire/

    The crash of EgyptAir flight 804 into the Mediterranean Sea that killed 66 people was caused by a hot Apple product … according to a new suit.

    The families of several of the victims of the May 19, 2016 crash claim the tragedy was due to the co-pilot’s iPhone 6S or iPad mini overheating in the cockpit and catching fire.

    According to the docs … an investigation revealed the device ignited and led to a bigger fire in the cockpit, which ultimately took the plane down.

    It should be noted, however — some industry experts have questioned this phone theory …

    Reply
  32. Tomi Engdahl says:

    Smartphone Explodes, Flying Shrapnel Hits Owner in the Head and Kills Him
    Two different phone models currently being investigated
    https://news.softpedia.com/news/smartphone-explodes-flying-shrapnel-hits-owner-in-the-head-and-kills-him-521656.shtml

    Exploding smartphones have become quite a problem for the entire industry, as in some extreme cases, they can lead to injuries suffered by their owners or even death.

    This is what happened recently to Malaysian Ministry of Finance-backed Cradle Fund Sdn Bhd CEO Nazrin Hassan, who was killed by what his brother-in-law says was flying shrapnel from a phone that burst into flames.

    Specifically, the brother, whose name was not disclosed, says Nazrin was charging his two phones, a BlackBerry and a Huawei, in his bedroom when one of them exploded, setting the room on fire. While the police say the man probably died from smoke inhalation, the brother-in-law says that what actually happened was that debris from the exploded phone hit Nazrin in the head, causing a severe trauma which eventually led to his death.

    “He had two phones, one Blackberry and a Huawei. We don’t know which one exploded.

    “No word from smartphone makers”

    The police say there’s actually a bigger chance that the death was caused by the fire in the room, which led to smoke intoxication since Nazrin couldn’t get out of the bedroom.

    Mobile phone explosion blamed for death of Cradle CEO
    https://www.themalaysianinsight.com/s/54886

    A mobile phone on the bed or bedside that exploded while being charged could have caused the bedroom fire and the death of Cradle Fund Sdn Bhd CEO Nazrin Hassan yesterday, according to the family.

    Reply
  33. Tomi Engdahl says:

    Are over-discharged lithium cells safe? (And how to test for damage.)
    https://www.youtube.com/watch?v=sRwoYJyjZNo

    Most of Poundland’s power banks in this style come completely discharged due to the higher than usual quiescent current of the circuitry. I wanted to know if that was a serious issue or not.

    Reply
  34. Tomi Engdahl says:

    Altmetric: 29More detail
    Article | OPEN | Published: 22 July 2016
    Mechanism of the entire overdischarge process and overdischarge-induced internal short circuit in lithium-ion batteries
    https://www.nature.com/articles/srep30248

    Lithium-ion batteries connected in series are prone to be overdischarged. Overdischarge results in various side effects, such as capacity degradation and internal short circuit (ISCr). However, most of previous research on the overdischarge of a cell was terminated when the cell voltage dropped to 0 V, leaving the further impacts of overdischarge unclear. This paper investigates the entire overdischarge process of large-format lithium-ion batteries by discharging the cell to −100% state of charge (SOC).

    The safety of lithium-ion batteries exposed to extreme conditions has been analyzed in previous studies in terms of thermal runaway6,7, overcharge8, overdischarge9,10, and internal short circuit (ISCr)11,12,13. Overdischarge is a common type of abuse that may lead to safety problems, such as ISCr9. Batteries are increasingly subjected to the conditions of overdischarge as greater numbers of cells are connected in series for a system requiring high voltage, such as electric vehicles14. Therefore, overdischarge and its impact on batteries must be investigated.

    Several previous studies have cast light on the overdischarge mechanisms of lithium-ion batteries

    ISCr in lithium-ion batteries is under intensive study because of its significant impact on the batteries’ safety.

    This research investigates the entire overdischarge process and overdischarge-induced ISCr of large-format Li-ion batteries with an LiyNi1/3Co1/3Mn1/3O2 (NCM) cathode and graphite anode.

    The overdischarge-induced ISCr is likely to occur when lithium-ion batteries are connected in series with great inconsistency. Moreover, the ISCr induced by overdischarge is well controlled without any mechanical deformation or foreign substance.

    The authors wish to note that the capacity ratios of negative to positive electrode have impact on the electrochemical reaction of Cu oxidation. To be specific, given an increased capacity ratio of negative and positive electrode, i.e. more active materials on the negative electrode, the occurrence of the potential of Cu dissolution at the negative electrode will be delayed, thereby postponing the Cu collector dissolution to an SOC more negative than −12% (−15%, −20% etc.).

    Reply

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