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Thread: greatest danger using li-ion cells occurs during re-charging

  1. #31
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    Default Re: greatest danger using li-ion cells occurs during re-charging

    its funny how you say you wouldnt use a cheap charger, kinda suggesting that normal people need to plunk down $100 for a charger, with some cute brand name, and complex capacity to do things.
    yet when they blow up the cells in TESTING, what do you think they use ? A High amperage hobby charger.

    because these overpriced chargers need a expert practicaly to operate them Correctally, and CAN exceed the specs for a cell, mabey a expert would want to use them, but there is no need for the consumer to try and charge FASTER to be safer.

    lots of these cells are tested to 5V <--- yup WAY over, to see if they will start a fire, and they do not, untill you increase the AMPerage too.

    while telling people to avoid cheap chargers, that go OVER spec when charging, is a good idea. The TOO high ones need to be identified, but the current on a cheap charger is so low, that catastrofic failure is LESS likly than a improperly used FAST charger.

    if people aint gonna plunk down the cash , and time , and read manuels, they are better off with a LOW amp rate, then a High amp rate charger.
    look at the specs for the Caused Fires, they are always pumping in some major juice.

    ID the junk, and stop the sale of it alltoghether, its not good enough to say "pull it when its green" , it should be the thing sucks send it back, dont use it.

    there are a lot of good SLOW chargers, and the day you see people setting them up out back to blow up batteries, you can convince others that they will.
    Wheras the high end hobby chargers Misused are what you CAN/DO start a fire with.

    we need good chargers, consumers dont need FAST chargers, nothing good will come of that, and proof of that is What exactally were each Fire causing event using? High end RC fast chargers, and fast high amp laptop chargers.

    if i was staging a fire event, the last thing i would use is a nano.
    ID the junk , but dont increase the rate.
    Last edited by VidPro; 04-30-2007 at 09:46 PM.

  2. #32
    *Flashaholic* LuxLuthor's Avatar
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    Default Re: greatest danger using li-ion cells occurs during re-charging

    VidPro, you make some good points...and I agree with most everything you say. However, in reality there has not been much use or testing of the type of Li-Ion cells we are using from AW over a long time, and in larger diverse applications, chargers, and with the kind of sample size you have in the RC community with LiPo's. I don't know how long AW has been selling his Li-Ion's here, but as the cells age, there may be more problems develop with them.

    I think it is very reasonable that it would be the "Hobby Chargers" that have the higher amperage which would be more likely to cause problems, but we really don't know how much of the Li-Ion problems will be related to those stronger chargers. I don't expect to see as many disasters with the Li-Ion cell users not being as likely to push their cells as compared to the RC users with LiPo, but it is fair to extrapolate with their experiences.

    I suspect there are a few others who had this type of "clandestine explosion" like hburner posted...and just don't want to talk about it. We don't know what his charger setup was but it seemed to be something from MAHA and some other charger or two. It would be nice to get more specifics so we know what was used.

    In the case of Norm's exploding Li-Ion cell post here, remember he only was charging a single 14500 cell with the Alin universal Lithium charger set on "2 cells" and that charger only outputs 500 mA, so it is not necessarily a high amp charging issue. The new example is apparently combined with a questionable/defective cell....but I'm guessing he was using a low amp charger.

    The problem is whether people will know they have a defective cell, and then how it then behaves with even a low current charger.

  3. #33
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    Default Re: greatest danger using li-ion cells occurs during re-charging

    Hello VidPro,

    Here is the reason people move up to more powerful chargers for Li-Ion cells...

    To keep track of things, you need to attend to your charge. A good charge rate is around 0.5C - 0.7C. The maximum charge rate is 1C. At 1C it usually takes an hour and a half or two hours to complete the charge. At 0.5C, this time is extended.

    Some people have lots of time and can attend to their charging all day while charging at low rates. Others, prefer to spend a couple to three hours charging, then they have other things they want to do.

    I am charging an 11.6 Ah Li-Ion battery right now. Charging at 10 amps means that the charge will be finished before I am ready to go to bed. If I were charging at 500 mA, it would take around 32 hours. I am not staying up that long to baby sit the charge.

    Now, when I go to charge my 330 mAh or 600 mAh cells, I set things up a lot differently, and charge at lower rates. It is nice to have the capability to also charge large batteries when you need to.

    I think the problem is that people jump on the Li-Ion bandwagon without thinking the whole thing through. People are interested in a lightweight light that is very bright and that draws them in. All of the sudden they have a light that is using Li-Ion cells, now they have to figure out how to recharge those cells.

    I believe this is what LuxLuthor ran into. Fortunately, he is taking the time to learn about Li-Ion chemistry and is proceeding cautiously while he is figuring things out.

    Slow charging has its place, but it isn't a universal answer.

    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...

  4. #34
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    Default Re: greatest danger using li-ion cells occurs during re-charging

    most may not realize it, but we on CPF are on the bleeding edge of consumer use of loose li-ion cells.

    information concerning safe use of loose li-ion cells is still constantly evolving.

    I'm not a battery expert, nor do I pretend to be one. but I do know who the battery experts are. IMHO Silverfox, Newbie and JS are some of the most knowledgeable folks around.

    due to the bewildering combinations possible with loose consumer li-ion cells and chargers. safety with li-ion cell use has to start at the cell level.

    Meaning protection needs to be at cell level in the form of built-in overcharge protection for loose consumer li-ion cells.

    loose bare li-ion cells are originally meant for professional battery pack builders who will place protection circuits in final product.

    when you purchase loose li-ion cells from US companies. typically requires signing off of safety disclaimers. here's one Tenergy uses http://www.all-battery.com/datasheet...eAgreement.pdf

    VS overseas li-ion suppliers require no such disclaimers. for all practical purposes, they operate without liability for possible accidents.

    this is a good thread for information about DSD and new Pila chargers. http://www.candlepowerforums.com/vb/...9&page=1&pp=20

    can you pick out 14500 li-ion cells from identical looking AA NMH cells?


  5. #35
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    Default Re: greatest danger using li-ion cells occurs during re-charging

    Quote Originally Posted by LuxLuthor
    In the case of Norm's exploding Li-Ion cell post here, remember he only was charging a single 14500 cell with the Alin universal Lithium charger set on "2 cells" and that charger only outputs 500 mA, so it is not necessarily a high amp charging issue. The new example is apparently combined with a questionable/defective cell....but I'm guessing he was using a low amp charger.

    The problem is whether people will know they have a defective cell, and then how it then behaves with even a low current charger.
    it might put out 500ma, but then it was at 7.2V, and it probably had a much higher voltage differential than intended, and might have pushed more like 750 or 1000ma.
    but indeed that is a good example. doesnt relate to trashing a little weasily nano charger that ONLY charges to a max of ~4.2, and would not have that problem. those types of chargers wont even go to 36V at 4amps :-)

    I have charged "defective" cells for DAYS, and DAYS, with them heating up, at .4-.5C rates, and they heat up. this particular set of cells was trash from age, and deep discharge, and was heating up, but keeping the rate low, i could not get multiple cells to even open up, let alone fire.
    Last edited by VidPro; 05-01-2007 at 03:18 AM.

  6. #36
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    Default Re: greatest danger using li-ion cells occurs during re-charging

    Quote Originally Posted by SilverFox
    Hello VidPro,

    I am charging an 11.6 Ah Li-Ion battery right now. Charging at 10 amps means that the charge will be finished before I am ready to go to bed. If I were charging at 500 mA, it would take around 32 hours. I am not staying up that long to baby sit the charge.

    Slow charging has its place, but it isn't a universal answer.

    Tom
    in the same sence while i was slow charging HUGE D cells with no problems for weeks on end and now for years, the first time i handed it to a "shultz/triton" user they slammed 1C into it and had a massive fire in "a few minutes" (thier words).

    it isnt a universal answer at all, experts , and people who Learn everything they need to know, indeed SHOULD be using a great charger like that. but from what we have seen, the average person and the person having a lot of FUN :-) can have more problems fast.

    -----------------------------------------------------

    reguardless , its like this with everything, sombody plunks down 250$ for a light, a charger, a car, some knife, some cool gadget, and EVERYONE should do the same thing. so just for the practicality of plunking down 250$ everytime somone on a forum thinks its the "best thing in the world", WHEN its great for experts, and people in the know, and people with to much money.

    its not a reason to trash every other item out there that costs 1/12th that and can do the job.
    meaning my 1litre car , would never pass the muster at a monster truck convention, but it still leagally does what any car can do, and it aint got a scratch on it :-)

    there are some people who overclock thier 2500Mgz Cpu to 5400Mgz, dance all over the forum telling how wonderfull it is. but the rest of the people following thier advice, tried to return thier fried $200 processor :-).

    sometimes experts forget how much time and effort and thought went into thier knowlege, and how dum the rest of us can be.
    Last edited by VidPro; 05-01-2007 at 03:41 AM.

  7. #37
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    Default Re: greatest danger using li-ion cells occurs during re-charging

    take another example, just for the sake of examples.
    people had been charging ni-mhys for some 20 years, then along comes the "best charger in the world" those 900 and 9000 untested digital masterpieces. plunking down huge sums, charging at high rates. suddenly things are melting .
    set these digital items incorrectally, or use them evil crap batteries that everyone in the world owns, and it Could be a bigger problem, than the "crudiest charger in the world".

    i am not saying that ANY of it is "bad" , but that "improvements" often have as many ramifications, as the old stuff. so recommendations for moving way up in a world that you dont yet understand, are not going to "solve" problems by themselves.

    one more point to the side, wasn't it high end RC chargers that were doing SEIRES charging without balancing? if these companies and thier chargers were so great of items, why did it take them so long to get balancing taps?
    To compare what THEY DID, to your simple little parellel non-series charger, is crasy, it was thier seires charing without balancing, by those brand name chargers that caused loads of the problems that everyone gets all worried about.
    ok Charring, charging , same differerance :-) you get the idea.
    Last edited by VidPro; 05-01-2007 at 04:35 AM.

  8. #38
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    Default Re: greatest danger using li-ion cells occurs during re-charging

    Quote Originally Posted by VidPro
    in the same sence while i was slow charging HUGE D cells with no problems for weeks on end and now for years, the first time i handed it to a "shultz/triton" user they slammed 1C into it and had a massive fire in "a few minutes" (thier words).
    I was thinking about what various people have written regarding overcharging, and was wondering if it's possible that extended low-rate overcharging might well not be enough to blow a cell, but could put a cell in a state where it was then particularly vulnerable to high-rate charging it might normally not have problems with?

  9. #39
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    Default Re: greatest danger using li-ion cells occurs during re-charging

    Quote Originally Posted by uk_caver
    I was thinking about what various people have written regarding overcharging, and was wondering if it's possible that extended low-rate overcharging might well not be enough to blow a cell, but could put a cell in a state where it was then particularly vulnerable to high-rate charging it might normally not have problems with?
    overcharging CAN indeed cause the same issues that over-discharging can, set the cell up for overheating when its charged.
    overcharging even very very slowly, for a Long time will puff a li-poly, or open up a cell.

    but most of the junk china slow rate chargers were Not going over 4.25, ever, green light or not. some are based on cheap protection curcuits.
    and really ALL the batteries should have thier OWN protection, reguardless.

    they wouldnt even SELL me cells , long ago, untill i defined what type of protection i would use on them. Seperated unprotected cells are for pack replacments, and pack making, packs that would have not only protection but thermal disconnect of some sort.
    but heck protection curcuits are 2$ what was the problem? other than hotwires :-)

    if some of them are going +-.05v of 4.20, then they are still in spec, if they are going to 4.35v, then we should be saying "Dont Use it" if its a problem. we know of one that people claim that is what it does, can we call a hoe a hoe?

    besides who puts the name "FIRE" on a li-ion battery or charger anyways :-) thats just asking for it.
    Last edited by VidPro; 05-01-2007 at 04:47 AM.

  10. #40

    Default Re: greatest danger using li-ion cells occurs during re-charging

    Quote Originally Posted by Phredd
    Is #7, "don't over-discharge"?
    I think #11 should be Phredd's "don't over-discharge". Hburner's story is a good reminder of that. See Tom's info here: http://candlepowerforums.com/vb/show...37#post1990837

  11. #41
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    Default Re: greatest danger using li-ion cells occurs during re-charging

    many thanks for posting that excellent link!

    it's also covered under
    #6. don't use li-ion cells in series without protection circuits.
    #3. use li-ion cells with internal protection circuits

    there's so many different gotchas with li-ion usage. it's extremely difficult to point all of them out without information overload!

    due to myriad of combinations possible with loose cells, lights/packs without protection circuits cells goes into and all the different chargers available. protection for loose li-ion cells is best at cell level. this safeguards against dangerous combinations.

    unfortunately hotwires can draw current in excess of 3C.
    internal protection PCB in cells see this as a dead short.

    soft start circuits, double clicking, larger number of cells in series, larger cells with higher current ratings, pilas ($18ea) and using bare cells are some of possible solutions being explored.

    safest use of li-ion cell is in singles. this includes picking a light that uses one cell and re-charging in singles.

    if you are using bare li-ion cells... yank cell at first sign of dimming. immediately measure cell voltage for first few uses to establish if over discharge is occurring. for all practical purposes, cells is empty under 3.5V. your goal is to yank cell before it goes below 3.5V.

    cells can recover if exposed briefly below 3V. damage can occur with ONE overdischarge. which will not show until you try to recharge cell.

    there's evidence dentrites can form during discharge at higher currents than mfg spec's and during extended charging at low charge rates. most mfg recommend .5C to 1C charge rates.

    dentrites form as sharp crystals which can pierce internals, leading to dead shorts. which will not show up until cell is fully charged.

    Quote Originally Posted by ckthorp
    I think #11 should be Phredd's "don't over-discharge". Hburner's story is a good reminder of that. See Tom's info here: http://candlepowerforums.com/vb/show...37#post1990837

  12. #42
    *Flashaholic* LuxLuthor's Avatar
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    Default Re: greatest danger using li-ion cells occurs during re-charging

    More good information. I think cy is right about us being on the bleeding edge of loose Li-Ion cell use. Scary thought. I think the best answer is the Saphion technology being used in more common loose cell sizes.

    I think you should make #11 "Do Not solder the contact ends of Li-Ion cells." If Li-Ion packs are desired, only apply solder to the manufacturer welded contact strips, keeping heat away from contact terminals.

  13. #43

    Default Re: greatest danger using li-ion cells occurs during re-charging

    Could always build one of these instead of soldering: http://www.philpem.me.uk/elec/welder/

  14. #44
    *Flashaholic* LuxLuthor's Avatar
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    Default Re: greatest danger using li-ion cells occurs during re-charging

    Quote Originally Posted by ckthorp
    Could always build one of these instead of soldering: http://www.philpem.me.uk/elec/welder/
    LOL...yeah right, just what we all need to be experimenting with....on top of using Li-Ion loose cells, and in series, now we should try making a "Mr. Wizard - Li-Ion contact welder." God help us.

  15. #45

    Default Re: greatest danger using li-ion cells occurs during re-charging

    Just a thought - what about making a housing for a Li-Ion charger so that any explosion/fire is confined so that it does minimal damage?

    This could be as simple as sitting your charger in a .50 ammo can, and place the charger on a firebrick. No lid, of course....but a kB/meltdown would probably be well contained in the can.

  16. #46
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    Default Re: greatest danger using li-ion cells occurs during re-charging

    already discussed and covered many time on RC forums.

    do a google on lipo bag.. they also make a ceramic charge pot. these mostly contain, but sometimes not... fumes are not contained.

    a fireplace insert with steel doors may be one of the best spots to do charging. it'd contain any fire and vent too.

    Quote Originally Posted by CDI
    Just a thought - what about making a housing for a Li-Ion charger so that any explosion/fire is confined so that it does minimal damage?

    This could be as simple as sitting your charger in a .50 ammo can, and place the charger on a firebrick. No lid, of course....but a kB/meltdown would probably be well contained in the can.

  17. #47
    *Flashaholic* LuxLuthor's Avatar
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    Default Re: greatest danger using li-ion cells occurs during re-charging

    I do all my Lithium charging now in the garage with concrete floor, or fireplace, or outside if warm enough. The toxic fumes are a concern that the various enclosures & Lipo Bag don't address alone.

  18. #48
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    Default Re: greatest danger using li-ion cells occurs during re-charging

    Hello LuxLuthor,

    This might be a good time to discuss cold temperature Li-Ion charging.

    Li-Ion cells should not be charged at ambient temperatures of 32 F or below. There is some concern that there may be some issues at ambient temperatures below 50 F.

    I am not sure what the temperature is in your garage, but if it drops below 50 F, you may want to rethink your charging procedure.

    Fred Marks at www.fmadirect.com limits the maximum voltage on Li-Po batteries to 4.1 volts per cell when the temperature is cool. He claims that the normal 4.2 volt charge can damage cells when the temperature drops.

    I have not done any testing on this, so I can not directly comment on it. Fred does a lot of testing, and is a trusted resource.

    I believe the damage is similar to slightly overcharge cells. You loose cycle life. I don't believe this causes a rapid vent with flame incident.

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

  19. #49
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    Default Re: greatest danger using li-ion cells occurs during re-charging

    Well, kind of hard to contain the fumes or gas because you'd be containing the pressure too. If something like the Battery Bunker that can contain the explosion but if you made it airtight too, it would explode in a million pieces. How do you vent pressure without vent the toxic fumes??
    Bill

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  20. #50

    Default Re: greatest danger using li-ion cells occurs during re-charging

    Quote Originally Posted by wptski
    How do you vent pressure without vent the toxic fumes??
    Could you build a stiff but slightly stretchy enclosure (to reduce the peak pressure) and then just use a couple/three of those P100+organic+chlorine respirator filter canisters that they sell at the hardware store to filter the exiting fumes? What kind of volumes are we talking about here (I've never personally witnessed a vent-with-flames incident)? What kind of pressure profile is there? During unenclosed charging, is it typically "*boom* and done" or more of a half second/few seconds flaming+hissing kind of event?

  21. #51
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    Default Re: greatest danger using li-ion cells occurs during re-charging

    Yeah! Go ahead and build one then. Stiff but stretchy material? What would that be?? There is a rather long thread here with video/audio of 123 lithium explosions/fires to view.
    Bill

    I'm a retired mechanic not a electronic/electrical engineer!

  22. #52

    Default Re: greatest danger using li-ion cells occurs during re-charging

    You don't consider something like heavy rubber to be stiff but stretchy which provides compliance but is much less likely to have a hole burn through it by a stray small piece of debris? Why the sarcasm?

    I've watched a few videos now. It seems like *boom* is restricted to enclosed cells (though I haven't seen any videos of that). The unenclosed cell videos that I've now watched seem to be a fairly prolonged burning process. The LiPoSack people even set one off inside of a glass fish tank with weighted down cardboard on the top. So there really isn't much of a shockwave, just reasonable gaseous volume produced on the seconds order-of-magnitude time scale.

    The way I see it, a battery charging safe needs to have a number of attributes. These include: non-flammable construction, power inlet for charging leads, volume compliance in order to absorb the gas produced by a rupturing battery, and either a lot of volume to hold the entire gaseous output or an output filter to reduce the concentration of output fumes.

    There was a spark-and-flame filter I built for some model rocket parachute ejection tests. That filter was to stop the sparks and flame produced by burning black powder. It was essentially a wad of very coarse steel wool inside of a PVC pipe which stopped flaming particles from burning the 'chute. A similar device could be used to connect a sealed charging enclosure to a weatherbaloon.

    What battery can I use to test such a device with, as cheaply as possible? I assume people are testing with batteries near their end-of-life?

  23. #53
    *Flashaholic* LuxLuthor's Avatar
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    Default Re: greatest danger using li-ion cells occurs during re-charging

    ck, I didn't think wptski's comment had sarcasm in it....just questioning what could there be that would be stiff but stretchable.

    The problem I see with anything rubber or flexible is the flames/heat which would melt & catch it on fire....which is why the Lipo Sack was more of a non-flammable cloth fiber type thing. Don't know if they used a Kevlar type fabric...but must have been something like that....and which doesn't control the smoke/fumes.

    It seems you would need an industrial type ventilation fan to contain the amount of smoke I have seen in several videos, including this one at PC PitStop with the computer battery pack. I believe those were individual Li-Ion cells similar to what we use....I doubt they used LiPo for those batteries.

    There is actually a very good read by the guys that did that video at PC Pitstop here. The guy they are interviewing was the VP of Engineering at Gateway, and he covers a lot of good points.

    I don't know of anyone who has done an intentional blow up of individual Li-Ion cells to see if they sometimes smoke/fire like the lipo's. We never heard back from that person posting the second example (besides Norm's example) as to more details of what happened.
    Last edited by LuxLuthor; 05-09-2007 at 03:12 PM.

  24. #54

    Default Re: greatest danger using li-ion cells occurs during re-charging

    Ok. If no sarcasm was intended, I apologize. Regardless, I think that the spark and flame arrestor I used with my rocket ejection device could actually work well in this application. I'm going to give it a shot when I have time.

  25. #55

    Default Re: greatest danger using li-ion cells occurs during re-charging

    Here's some good info on CR2 and CR123 battery gas volume output. http://www.fire.tc.faa.gov/pdf/04-26.pdf It indicates that in a 10-cubic-meter air-tight chamber, the pressure increase caused by 16 burning CR2 batteries, ignited via a firepan underneath, was about 2psi. The temperature rise was about 15 deg F. So I believe that we are dealing with volumes which could reasonably be contained.

  26. #56
    *Flashaholic* LuxLuthor's Avatar
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    Default Re: greatest danger using li-ion cells occurs during re-charging

    Quote Originally Posted by ckthorp
    Here's some good info on CR2 and CR123 battery gas volume output. http://www.fire.tc.faa.gov/pdf/04-26.pdf It indicates that in a 10-cubic-meter air-tight chamber, the pressure increase caused by 16 burning CR2 batteries, ignited via a firepan underneath, was about 2psi. The temperature rise was about 15 deg F. So I believe that we are dealing with volumes which could reasonably be contained.
    I don't think I read the same report as you....or I have a different understanding of some of the information.
    • I do not remember my physics enough to figure out the various effects of Charles Law, Boyles Law, etc....but this result of 2.6 psi increase in pressure from exploding 16 CR2 cells inside of a 10 cubic meter (or 33 cubic foot) chamber would translate to a much higher pressure when contained in a smaller volume box that a person would use for battery charging.

    • I am not sure how their ignition with a container of alcohol with that heat, flames, consumption of oxygen maps onto our battery charging scenario.


    • They really only used small disposable Lithium CR2 & 123A cells, so I'm not sure how that chemistry compares to what we are doing, but my reading of this pdf talks about an increase of 650° F in a 64 cubic foot chamber with vents and using alcohol to trigger.

  27. #57

    Default Re: greatest danger using li-ion cells occurs during re-charging

    Quote Originally Posted by LuxLuthor
    I don't think I read the same report as you....or I have a different understanding of some of the information.
    • I do not remember my physics enough to figure out the various effects of Charles Law, Boyles Law, etc....but this result of 2.6 psi increase in pressure from exploding 16 CR2 cells inside of a 10 cubic meter (or 33 cubic foot) chamber would translate to a much higher pressure when contained in a smaller volume box that a person would use for battery charging.

    • I am not sure how their ignition with a container of alcohol with that heat, flames, consumption of oxygen maps onto our battery charging scenario.


    • They really only used small disposable Lithium CR2 & 123A cells, so I'm not sure how that chemistry compares to what we are doing, but my reading of this pdf talks about an increase of 650° F in a 64 cubic foot chamber with vents and using alcohol to trigger.
    Ah, that's what the weather baloon was for. It's the space for the extra volume. I've got one on order. They're reasonably priced and have plenty more volume than a 10 cubic meter box.

    I suspect burning the lithium is burning the lithium however the fire is started.

    I suspect that on the FAA laptop battery, there was probably insufficient heat.

    The 650 Deg. F increase was a peak temperature directly over the burning batteries, not an average temperature increase over the entire chamber. Also, the temperature testing chamber was only 64 cubic feet, or only about 2 cubic meters.

    There were two different testing chambers. The first was a 64 cubic foot peak temperature, video filming, and airline cargo bag material testing chamber. The other one was a sealed 10 cubic meter chamber for testing the average temp increase as well as pressure increase from combustion byproducts. While only using small CR2 and CR123 batteries, 16 of them probably is more active mass than one 18650 cell. Anyway, I was just pointing it out as a reasonable baseline for exploding batteries, not that it was going to be 100% comparable to a rechargable fire.

  28. #58
    *Flashaholic* LuxLuthor's Avatar
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    Default Re: greatest danger using li-ion cells occurs during re-charging

    You looked at that video I linked, right? Good luck on this, I don't think anyone else is gonna try to put together all the elements you are talking about. I just use my fireplace or garage/outside if warm enough.

  29. #59

    Default Re: greatest danger using li-ion cells occurs during re-charging

    Yup. I looked at the video. I think I'll still give it a shot. $40 for safe indoor charging really isn't that much expense.

    Problem is, that in MN, there really isn't an alternative to indoor charging in the winter. The garage is certainly below freezing. The fireplace would be below freezing pretty quick after I opened the flue without a fire lit in it. That, or I'd be letting dollars worth of heat out, negating the main selling point of rechargable batteries -- reduced operating costs.

    I'll start a new thread once I get things together. What's the cheapest way to start testing this rig? Tearing apart used laptop batteries from eBay?

  30. #60

    Default Re: greatest danger using li-ion cells occurs during re-charging

    Quote Originally Posted by LuxLuthor
    but this result of 2.6 psi increase in pressure from exploding 16 CR2 cells inside of a 10 cubic meter (or 33 cubic foot) chamber would translate to a much higher pressure when contained in a smaller volume box that a person would use for battery charging.
    Hi,
    10 cubic meters is 353 cubic feet.
    If you used a wood stove insert in your fireplace, it might be 28 inches x 18 inches x 22 inches (about 6.41667 cubic feet).
    +2.6 psi x 353 cubit feet
    = 6.41667 cubit feet x +143 psi
    With +143 psi (or 10 atmospheres), you will need some serious seals and hinges if it was airtight.

    -wjb3
    Last edited by wjb3; 05-10-2007 at 07:12 AM. Reason: correct equation

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