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Thread: Li-Ion protection technology and possible dangers

  1. #91
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    Default Re: Li-Ion protection technology and possible dangers

    Lithium-ion Battery Safety News

    From:
    http://www.ansi.org/news_publication...articleid=1307

    Group Formed to Develop Safety Standards for Lithium-ion Batteries

    " In direct response to these recent events, ANSI member and accredited standards developer IPC - Association Connecting Electronics Industries (IPC) has announced that it will move immediately to develop safety standards for lithium-ion batteries. The initiative will be led by IPC痴 OEM (original equipment manufacturer) Critical Components Committee, which includes technical experts from ANSI members Dell Computer, Hewlett-Packard, Apple Computer, IBM, Motorola, Lucent Technologies, Intel, and Cisco Systems."

    I consult at one of the member companies so I received a notice, but I often Google: +"lithium-ion batteries" +safety
    Last edited by NextLight; 09-10-2006 at 09:24 AM.
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  2. #92
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    Default Re: Li-Ion protection technology and possible dangers

    most of the attention has been focused rightly on Dell/apple/sony etc.

    but for out little niche, flashlights...

    so far no reported failures connected to li-ion usage, either single cell or mulitple cell lights have been reported. that's bare and/or protected cells.

    VS primary lithium cells, especially chinese private label lithium cells. when used in multi cell flashlights w/clickies have multiples failures reported with more coming in.

    suppliers with ten's of thousands private label chinese primary lithium cells in the pipeline probably are already aware of this problem. but will continue to sell, until supply is depleted.

    Newbie has posted his testing methodalogy in extreme detail. any mfg and/or retailer of chinese private label lithium cells could duplicate Newbie's tests that leads to venting with flames.

    Quote Originally Posted by NextLight
    Lithium-ion Battery Safety News

    From:
    http://www.ansi.org/news_publication...articleid=1307

    Group Formed to Develop Safety Standards for Lithium-ion Batteries

    " In direct response to these recent events, ANSI member and accredited standards developer IPC - Association Connecting Electronics Industries (IPC) has announced that it will move immediately to develop safety standards for lithium-ion batteries. The initiative will be led by IPC痴 OEM (original equipment manufacturer) Critical Components Committee, which includes technical experts from ANSI members Dell Computer, Hewlett-Packard, Apple Computer, IBM, Motorola, Lucent Technologies, Intel, and Cisco Systems."

    I consult at one of the member companies so I received a notice, but I often Google: +"lithium-ion batteries" +safety

  3. #93
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    Default Re: Li-Ion protection technology and possible dangers

    Hello Cy,

    I know the manufacturer of the Titanium cells has been advised to check out this thread and duplicate the testing at their own facility.

    I have not heard anything other than they have been presented with this information.

    Tom

    EDIT: I forgot what thread I was reading. The thread that the manufacturers of the Titanium cells was forwarded was the thread that NewBie is doing all the testing in. Not this thread... ENDEDIT
    Last edited by SilverFox; 09-11-2006 at 09:38 PM.
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  4. #94
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    Default Re: Li-Ion protection technology and possible dangers

    tom, that's good to know... I've always wondered if the same private label mfg in china makes both battery station and titanium cells.

  5. #95
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    Default Re: Li-Ion protection technology and possible dangers

    Great thread.

    Forgive me if I missed it, but can someone comment on what danger there might be if someone over-discharges a (single) lithium-ion cell and then attempts to charge it.

    Assumptions:

    - The cell was not abused other than the over discharge.
    - It may be quite over-discharged.
    - The application is a single cell application.
    - The cell with be charged by itself.

    Thanks!

    -john

  6. #96
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    Default Re: Li-Ion protection technology and possible dangers

    Hello John,

    Li-Ion chemistry becomes unstable when over charged or over discharged.

    Over discharging to a low voltage (below 2.3-2.7 volts under load, 3.0-3.5 volts resting) results in the copper current collector dissolving in the electrolyte. This dissolved copper is plated onto the anode on subsequent charges. This inhibits the utilization of the active material and results in reduced performance and life. If this is repeated several times, copper dendrites can form and can produce a short circuit in the cell. A short circuit will produce a localized hot spot in the cell. This local hot spot can start a run away reaction that terminates with "rapid venting with flame."

    Tom
    Behind every Great man there's always a woman rolling her eyes...

    Most batteries don't die - they are tortured to near death, then murdered...

  7. #97
    Flashaholic* John N's Avatar
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    Default Re: Li-Ion protection technology and possible dangers

    So basically the discharged cell is safe, but if you keep using it you risk the cell shorting itself and venting?

    Thanks,

    -john

  8. #98
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    Default Re: Li-Ion protection technology and possible dangers

    no li-ion cell flashlight failures, single or mulitple cells have been reported on cpf. there have been reported failure connected to li-ion chargers.

    li-ion cell's chemistry has no peak when charging. but will accept a charge for so long as you deliver current to cell. that's why it's recommended not to charge li-ion cells unattended.

    most low end li-ion chargers will not terminate charge at 4.2V. but will continue to trickle charge cell until charger is unplugged or cell removed.

    high end li-ion chargers like shultz and triton will go thru multi-stages during a full charge cycle.

  9. #99
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    Default Re: Li-Ion protection technology and possible dangers

    Quote Originally Posted by SilverFox
    Hello John,

    This local hot spot can start a run away reaction that terminates with "rapid venting with flame."

    Tom
    I like how they come up with terminology that sounds so subdued, when it is more like a rocket engine going off.

  10. #100
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    Default Re: Li-Ion protection technology and possible dangers

    Hello NewBie,

    The other term that cracks me up is "rapid dissassembly..."

    Tom
    Behind every Great man there's always a woman rolling her eyes...

    Most batteries don't die - they are tortured to near death, then murdered...

  11. #101
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    Default Re: Li-Ion protection technology and possible dangers

    Toshiba joins Dell and Apple in recall of Sony Lithium Ion batteries:

    TOKYO, Japan (AP) -- Toshiba is recalling 340,000 laptop batteries worldwide made by Sony Corp., the latest in a series of problems for the company.

    Dell asked customers to return 4.1 million faulty laptop batteries, while
    Apple recalled 1.8 million batteries worldwide.


    http://www.cnn.com/2006/TECH/ptech/0....ap/index.html

  12. #102
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    Default Re: Li-Ion protection technology and possible dangers

    Hitachi Recalls 16,000 Sony Batteries

    Add Hitachi to the list.

    http://today.reuters.com/news/articl...&from=business

  13. #103
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    Default Re: Li-Ion protection technology and possible dangers

    Also add IBM, Lenovo, and possibly Fujitsu.

    http://www.businessweek.com/technolo...eek+exclusives


    Meanwhile, I ran across an old National Transportation Safety Board and the Federal Aviation Administration report about 14 Lithium battery failures and aircraft:
    http://www.ntsb.gov/events/2006/Phil...20explosion%22

    http://www.ntsb.gov/Events/2006/Phil...20explosion%22
    Last edited by NewBie; 10-10-2006 at 08:50 PM.

  14. #104
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    Default Re: Li-Ion protection technology and possible dangers

    Hi,

    That's interesting Newbie because they talk about other types of batteries being
    a problem too.
    Long time ago, i had a high powered battery short in my pocket by my keys.
    Got hot, very hot, but didnt smoke or flame.
    Take care,
    Al
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  15. #105
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    Default Re: Li-Ion protection technology and possible dangers

    Newbie, most interesting link to FAA document for battery failure in aircraft. the infamous lending of light purchased in beijing by a flight attendant is listed.

  16. #106
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    Default Re: Li-Ion protection technology and possible dangers

    Fujitsu Siemens now joins the Lithium-Ion recall frenzy.

    Batteries in some notebook computers from Fujitsu Siemens Computers can overheat, with a risk of fire. The company has recalled the batteries.

    Models affected:

    -A7640

    -A1640

    -M1405

    -M1424

    -M1425

    -M7405

    -M7424

    -M7425

    -Pro V2020

    http://pcworld.com/article/id,121397...1/article.html


    Fujitsu Siemens is recalling quarter of a million notebook batteries which might just burst into flames. The recall, sorry "proactive exchange program", concerns Amilo notebook computers with a battery model number ending G1L1. There are problems with batteries on Amilo O, A and Pro machines.

    Anyone with such a machine should stop using the battery immediately and only run it from AC power.
    http://www.theregister.co.uk/2005/06...all_batteries/


    I was asked if LG Lithium-Ion cells have ever been recalled. Yes, in May 2005, computer brand Apple, and also LG was involved in the earlier recall too, for combusting batteries:
    http://www.channelregister.co.uk/200...lls_batteries/
    and
    http://www.theregister.co.uk/2004/08...attery_recall/
    Last edited by NewBie; 10-10-2006 at 09:00 PM.

  17. #107
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    Default Re: Li-Ion protection technology and possible dangers

    So....how do you know when its time to recharge your rcr123 cells??
    If your not supposed to over charge them, how do you know??

    I have rcr123 3.0V cells w/IC from E-lectronics.com and was wondering if there was a good way to decide when to charge them while using them EDC. I'd rather not have to constantly test them for voltage, Is that what I have to do to avoid over discharging, and provide the proper care?????

    If I understand correctly, these cells have cirucits built in to protect them from low voltage, but is it suggested not to rely on that for a charging inticator.......?

    Im new to Li-Ion rechargables and do not want to add to "Bad Deal" statistics

    Sorry to , but I was wondering
    out of the darkness comes......well duh

  18. #108
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    Default Re: Li-Ion protection technology and possible dangers

    Hello Munkybiz,

    Welcome to CPF.

    Let's look at cell phones for a moment. Many people have cell phones powered by Li-Ion or Li-Poly batteries. While the cell phone does have a battery indicator, most people charge the phone up and the end of a days usage.

    You can use this same approach to your EDC light. You may have to do some testing at first, but you should quickly be able to get an idea of how often you need to charge. With infrequent use, you may only charge once a month. With more frequent use, once a week may be better. Sometimes you need to use it for an extended period of time and may have to charge after use.

    Some batteries have low voltage protection. I think that it is set too low and constantly running until the low voltage protection cuts in will damage your batteries and result in lower cycle life. It seems that Li-Ion batteries work best when they are only used to 80% of their capacity. Trying to extract the last bit of capacity takes its toll on the batteries longevity and performance.

    If you are in a situation where you need the run time, run the batteries into the ground. However, most of the time that is not necessary so be kind to your batteries and re-charge often.

    Tom
    Behind every Great man there's always a woman rolling her eyes...

    Most batteries don't die - they are tortured to near death, then murdered...

  19. #109
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    Default Re: Li-Ion protection technology and possible dangers

    Quote Originally Posted by flashlight
    Yeah, that's right & wonder if he ever got anything back on that investment & didn't get gypped instead ....
    No, I am still paying for this and has limited the things I can try.
    I have lost just about everything I own on this.


    One the cells,
    The first several batches if cells that had made (these were not sold) were quite dangerous. We finally got them to where I was sure they were safe and released them.

    The dangers of LI cells is real.
    Last edited by JonSidneyB; 11-05-2006 at 03:03 AM.
    The Creator of the protected RCR123

  20. #110
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    Default Re: Li-Ion protection technology and possible dangers

    (I知 not sure where to post this so I値l post it on the Raw thread as well as in the battery sub forum so the mods can just delete one if it is against)

    I just received the raw ns Cree. Tested it for about 10 min on high and some more on low, I suppose it ships with the batteries charged. Everything works fine but after using it I wanted to test the charger too and placed the battery in it.. The instructions state that the charging will probably last about 45 min (and in this case the light did not start to dim before charging so it should take less than that), and when it is charged it should stop charging and the led on the nano charger should change from red to green. Well, it is charging for about 9 hours now and it's red. Being an unprotected Li-ion I moved it to the balcony, just in case.
    I use a converter to plug it in as the UK (I thing the US is similar) standard is different than the European one that we use, but that should make no difference.
    Something like this:


    O, another question.

    Li-ions are sensitive to heat, so I suppose taking it with me to India if I'm going in a period/region with high temperature (like over 40 C ) is not a good idea?
    I知 also not sure if the charger works there?

    P.S. Rob is out of office so asking him is not possible at this time.

    Thanks,

    Goran
    Last edited by Goran; 02-02-2007 at 12:08 PM.

  21. #111
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    Default Re: Li-Ion protection technology and possible dangers

    Quote Originally Posted by Goran
    (I知 not sure where to post this so I値l post it on the Raw thread as well as in the battery sub forum so the mods can just delete one if it is against)

    I just received the raw ns Cree. Tested it for about 10 min on high and some more on low, I suppose it ships with the batteries charged. Everything works fine but after using it I wanted to test the charger too and placed the battery in it.. The instructions state that the charging will probably last about 45 min (and in this case the light did not start to dim before charging so it should take less than that), and when it is charged it should stop charging and the led on the nano charger should change from red to green. Well, it is charging for about 9 hours now and it's red. Being an unprotected Li-ion I moved it to the balcony, just in case.
    I use a converter to plug it in as the UK (I thing the US is similar) standard is different than the European one that we use, but that should make no difference.
    Something like this:


    O, another question.

    Li-ions are sensitive to heat, so I suppose taking it with me to India if I'm going in a period/region with high temperature (like over 40 C ) is not a good idea?
    I知 also not sure if the charger works there?

    P.S. Rob is out of office so asking him is not possible at this time.

    Thanks,

    Goran
    The same thing happened with the other battery though it was just barely used.

    There I san ォelectricサ sound, like zzzzzzzzzzzzz coming out when charging for some time, I don稚 know if it is normal or not?

  22. #112
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    Default Re: Li-Ion protection technology and possible dangers

    Guys,

    scary thread!

    I recall seing several threads reporting primary venting/exploding in flashlight...

    But I don't recall seing any report of these kind of event with li-ion. Is there any known case of li-ion venting/exploding in a flashlight so far?
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  23. #113
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    Default Re: Li-Ion protection technology and possible dangers

    Besides this Valence Video that was posted on page one showing Li Ion's being shot with a gun, I also found this other link showing a "Lipo Bag" video to put batteries in while charging to at least minimize the damage...but nothing gets the point accross like seeing the fire videos of these batteries.

    Here's another one on google video with what sounds like a couple of "good old boys."

    This is of a Laptop fire.
    Last edited by LuxLuthor; 03-16-2007 at 02:49 AM.

  24. #114
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    Default Re: Li-Ion protection technology and possible dangers

    so far no documented instance of li-ion venting/exploding in flashlight.

    a major portion of risks of using li-ion is during charging process. li-ion cells don't have a peak, but will accept a charge long as your deliver current to cell. when li-ion cell reaches 4.35v or so thermal runaway may occur, leading to venting with flames.

    so far very few li-ion cells have overcharge protection built-in. Pila and AW R123 high discharge comes to mind.

    here's an instance of li-ion cell exploding/venting with flames. universal "smart" charger with incorrect voltage setting overcharged a li-ion cell leading to explosion. user was lucky not to burn down house and no one was hurt. http://candlepowerforums.com/vb/showthread.php?t=152013

    amazingly this charger is still being sold on cpf. betcha most don't realize dangers of using this charger with wrong voltage could lead to explosion. http://candlepowerforums.com/vb/showthread.php?t=117653



    Quote Originally Posted by tino_ale
    Guys,

    scary thread!

    I recall seing several threads reporting primary venting/exploding in flashlight...

    But I don't recall seing any report of these kind of event with li-ion. Is there any known case of li-ion venting/exploding in a flashlight so far?

  25. #115
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    Default Re: Li-Ion protection technology and possible dangers

    Quote Originally Posted by cy
    so far no documented instance of li-ion venting/exploding in flashlight.

    a major portion of risks of using li-ion is during charging process. li-ion cells don't have a peak, but will accept a charge long as your deliver current to cell. when li-ion cell reaches 4.35v or so thermal runaway may occur, leading to venting with flames.

    so far very few li-ion cells have overcharge protection built-in. Pila and AW R123 high discharge comes to mind.

    here's an instance of li-ion cell exploding/venting with flames. universal "smart" charger with incorrect voltage setting overcharged a li-ion cell leading to explosion. user was lucky not to burn down house and no one was hurt. http://candlepowerforums.com/vb/showthread.php?t=152013

    amazingly this charger is still being sold on cpf. betcha most don't realize dangers of using this charger with wrong voltage could lead to explosion. http://candlepowerforums.com/vb/showthread.php?t=117653
    Yeah, Cy, I saw that thread, but for some reason it did not sink in about the danger with Lithium cells like watching the videos I posted.

    I now agree that Alin's universal charger is pretty easy to set for the wrong size battery pack voltage. The markings are small & hard to read, and the charger lists both the actual range (3.7 - 7.4 - 11.1 - 14.8 volts) of the cell packs on top, but also the higher voltage actually applied with the slider switch.

    This slider switch has the other set of "charging current" settings (4.2 - 8.4 - 12.6 - 16.8 volts) which adds to the confusion, myself included for a while. The switch does not even have a careful slot to make sure you are on the right charging current selection choice.



    IMHO, this charger should be recalled and no longer sold by Alin given that a number of users (inlcuding me) are using it to charge UNPROTECTED cells...I even apologize in advance to Alin for stating my opinion and linking his product. I think it is that important to even risk some num-nuts starting another LuxLuthor Jeers thread !

    I even sent him a link about all this a few weeks ago...but after being on this forum for about 18 months, I only tonight fully realize how dangerous charging these Lithium cells are. I'm sure most users still have no idea.


    The idea is to never charge these 3.7V cells any more than 4.2 Volts. I also now understand the importance of using protected cells. Watch the videos above that I linked.

  26. #116
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    Default Re: Li-Ion protection technology and possible dangers

    The possible confusion / incorrect setting of the selector switch is just one danger of using this charger. Neglecting to set it correctly is a very real problem which can happen to anyone, even an experienced and normally meticulous person.

    Another risk which should not be overlooked is the danger of charging Li-Ions in series, which this charger allows. Parallel charging of Li-Ions can be reasonably safe as long as the cells are not badly mismatched in voltage on starting the charge, but series charging is far more risky IMO and I would NEVER recommend it, even with protected cells! With unprotected cells the whole idea of a charger like this is a disaster waiting to happen, and I entirely agree it ought to be withdrawn.

    Lux, if you get flamed for saying that, I think there will be plenty of people on your side!
    Resistance is futile...

  27. #117
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    Default Re: Li-Ion protection technology and possible dangers

    Well after spending several hours reading and watching videos of the fires I saw, and despite the handy sales pitch of FiveMega's plug sticking out of the tailcap on some of his Li-Ion mods, I am no longer going to charge them this way.

    There is no way to do individual cell balancing using any of these FM type of battery packs like in this light. Cell balancing is done with most quality RC battery packs, and because they have individual charging wires going to each cell in the pack. Without that "individual cell charging" type safety measure, you can have a single cell in FM's setup develop a much higher voltage than others.

    As a result, that one cell that started with the higher voltagel can end up being charged with too high of voltage (since all the cells in the pack make it look like they are all having the same average lower voltage that the charger sees)...and leading to the fire.

    There is no safety even if a Schultze or Hyperion charger is used with this setup...because again the cells are all combined as one charging package.

    Does anyone know an effective way to modify FM's packs so you could have a safe 4S or 8S charging setup? I'm reluctant to solder onto the ends of these AW cells...especially with the protection circuit that would likely be damaged by the heat.

  28. #118
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    Default Re: Li-Ion protection technology and possible dangers

    When newbie first posted this (thanks jar) and I read it the first time. Hotwire mated to multi-cell li-ion packs had not been done, except in a few proto's.

    JS, Geneng, Bwaites and gang were front runners of the hotwire evolution. When JS was exploring what config to use for M6R, multi-cell li-ion was discarded in favor of NMH packs. Safety during charging was of major concern.

    with the proliferation of hotwires supported by li-ion cells. This warning has taken a whole new meaning.

    discharging li-ion cells faster than design spec's may lead to plating of anode forming a dendritic growth that can puncture separator, forming a dead short to cathode. I suspect this may be cause of many documented examples of RC packs catching on fire, not while in use for no apparent reason.

    this damage to cell may not show itself until after cell is in fully charged condition.

    High discharge rates (2C+) supported by rechargeable lithium multi-cell packs would be a short description of what RC folks have done for a number years.

    now exchange li-po packs for li-ion packs and we find very similar usage patterns between RC and Hotwire folks.

    a major difference is dangers of using high energy rechargeable li-po packs is widely known vs some of our hot wire folks may or may not have the foggiest notion about dangers of charging li-ion multi-cell packs.

    RC folks are much further down path of high intensive use of battery packs. most RC li-po packs contain balancing leads. which after introduction has resulted in a dramatic reduction in instances of lipo packs exploding/catching in fire.

    Now current trend is to use A123 cells salvaged from Dewalt battery packs. new A123 chemistry is much more resistant to catching on fire.

    unfortunately due space limitation of flashlights. combined with limited offerings of A123 type cells and it's lower energy density ratings has not caught on.

    now there's reports of AW's protected cell's circuit board failing when exposed to extreme cold conditions.

    recently with AW's introduction of protected C li-ion cells. multiple threads have been started by hotwire and other folks looking for a cheap li-ion charger.

    currently there is no such thing as a cheap good/safe charger that will safely charge at 1C rate. I've posted this already in multiple threads as a good starting point to find a suitable charger for li-ion cells.

    http://candlepowerforums.com/vb/showthread.php?t=157773

    http://candlepowerforums.com/vb/showthread.php?t=152013

    Quote Originally Posted by NewBie
    Now lets move on to pushing a Li-Ion cell beyond it's design:

    Operating Current Limits
    Manufacturer's do not just randomly pick out ratings for their cells. Many Li-Ion cells datasheets will specify a *maximum* 2C discharge rate. If a cell is rated for 650mAH, then it's 2C rating would be 1300mAH. This is the *absolute maximum* rate you are supposed to discharge the cell at. This does not hold true for all Li-Ion cells. In some cases it is less. In all cases, it is inherently sane (and imho very important) to go and actually look at the manufacturer's datasheet for the cells maximum discharge rate.

    So, just what happens if you push a cell too hard?

    In a Li-Ion cell, if you push the cell beyond the maximum discharge rate, you in essence are pulling excessive current from the cell. This often results in permanent damage to the Li-Ion cell. It may be gradual, or it may be more immediate.

    While discharging at high charging currents, the Li+ ion starts to diffuse improperly into the anode痴 graphite particles which starts a plating of lithium metal on the surface. This plating caused by high discharge current forms in a manner which causes dendritic growth that can puncture the separator and form a conductive short circuit to the cathode. In some cases these will be "soft shorts", where the cell has a momentary drop out of voltage. In other cases it can result in a chain reaction which results in very violent venting, or possible explosion. Even a venting stituation can be dangerous, and Li-Ion cells can vent with flame and hot molten metals, and very reactive hot Lithium.

    If you are pushing your cells beyond their ratings, sometimes you will just see a rapid reduction in cell capacity. If the cell doesn not explode or vent, your cell suffers an early death. This plated lithium metal mentioned above is quite reactive toward the cell's electrolyte and results in electrolyte decomposition at the anode, growing the thickness of the SEI layer. This will also increase internal resistance, and reduction of available electrolyte.

    Another situation that happens when running Li-Ion cells beyond their ratings is called "polarization". Polarization, is the inability to move lithium ions through the electrolyte, and in and out of the active materials, will greatly reduce the cell痴 performance.

    When building Li-Ion cell packs, where the cells are in series, another technique is used during the build process, above and beyond all the aforementioned protection devices and circuit. In this case, battery pack manufacturers will actually run the cells over a number of charge and discharge cycles. Then they will match cells with similar characteristics. This helps prevent the over discharge (dangerous) of one of the cells in the series pack. A weak cell in a pack may also get warmer than other cells in the pack. Above and beyond all this, the associated electronics in a series pack actually monitor each cells individual voltage, and have various mechanisms to protect from explosion and venting of the weak cell.

    The weak cell scenario also applies to the charging of the series pack. In this case, the weak cell may become fully charged before the rest of the cells. Then the cell starts to overcharge, which can result in venting and/or explosion. The electronics also protect against this scenario.

    Unlike NiCd, Lead-Acid, or NiMH, there is no natural mechanism for Li-Ion cell
    equalization during charging. This is another reason why the electronic protection circuits, and proper chargers are necessary. Otherwise you risk venting and/or explosion.

    In situations where packs may be exposed to an unbalanced external thermal gradient, the cells will not discharge at the same rate. In this case, it is even more important to have the electronic protection circuitry. Otherwise, once again, you risk the vent/explosion senario. Though, the proper way to deal with this is not to put the cells in a situation where there is a thermal gradient.


    I sure hope folks that are starting to buy some of the larger, and even more dangerous Li-Ion cells read and heed all the information presented so far.

    Edited for spelling.

  29. #119
    Flashaholic* LumenHound's Avatar
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    Default Re: Li-Ion protection technology and possible dangers

    Great post.
    Being aware of the dangers of pushing Li-ion cells beyond safe limits is something all who use them should know. There must a good number of modders who have never head about dendric growth causing internal soft & hard short circuits.

    This is particularly important with the higher capacity cells. They can turn into rocket motors if not used safely.

    Can you imagine the potential legal mess if a big cell like a 18500 or 18650 exploded "out of the blue" after 20-30 full discharges knowingly run above the manufacturers stated safe limits by the flashlight owner and injured a co-worker or neighbour?

    "Wow! That's pretty bright. Can I check it out?"
    "Sure, here you go, just don't point it at me."
    BLAMMO!!
    "My hand! My hand!"
    "Uh-oh."

  30. #120
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    Default Re: Li-Ion protection technology and possible dangers

    Let's visit Dendritic Growth and what is it?

    experienced it first hand when I worked at a production plating shop. during plating process, metal is applied by transfer of ions in a conductive solution traveling usually from anode made out of target material (say copper) to cathode target to be plated.

    where dendritic growth occurred was usually on racks parts were mounted on. dentrite formed like a crystal tree often forming sharp edges. it's these dendrite structures that could puncture internal insulating barriers causing a dead short.

    I suspect that some of the infamous laptop failures might have been from dendritic growths from li-ion cells being discharged in excess of rating.

    http://math.nist.gov/mcsd/savg/vis/dendrite/index.html


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