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Old Aug 06, 2003, 11:52 AM
Been There! Done That!
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Eugene, Oregon, United States
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Quote:
Originally posted by hoppy
Dave, in regards to "will contents burn", the answer is yes. The organic materials and the Al foil will burn.
From Kokam MSDS - "If heated above 130C, Cell(s) may explode/swell or leak."

hoppy
Explode!!!! Looks like that takes care of " they only swell up" as I was told and as has been posted! Glad I got rid of mine! (Flame suit on as usual as I put it on BEFORE I start posting in this thread!? Ha!)
boomer
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Old Aug 06, 2003, 01:28 PM
MKH
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Ohio
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Quote:
Originally posted by boomerace
Glad I got rid of mine! (Flame suit on as usual as I put it on BEFORE I start posting in this thread!? Ha!)
boomer
I won't flame you boomer! I use 2 and 3 cell lipoly packs, very carefully and attentively, and feel pretty comfortable with them. I slow charge, and use a small charger with knobs that I set myself. I only discharge at about 5C or less, and the packs are always pretty cool after a flight. I understand your reservations, and other folks too. I think maybe the sheer speed of lipoly development has had a backlash, or at least left many of us in a quandry. Before there was any real consensus on acceptable amp draws, we were already on to charge rates, assembling multiple series/parallel packs, fast charging, etc. I'm lucky. All I need are 2 and 3 cell packs and small brushless motors to keep my parkies happy. I've tried to keep up with these lipoly threads, but must admit, I get lost in it all. I hope everyone stays safe, regardless of what they fly.
Marcus
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Old Aug 06, 2003, 02:29 PM
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Boomer's just too old to change.

Us seventy-two-year-olds get along fine with LiPos.

- RD
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Old Aug 06, 2003, 03:19 PM
Been There! Done That!
boomerace's Avatar
Eugene, Oregon, United States
Joined Sep 2001
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Quote:
Originally posted by RD Blakeslee
Boomer's just too old to change.

Us seventy-two-year-olds get along fine with LiPos.

- RD
Not really I got rid of mine after I puffed one! My NiMH's don't puff and I have never had one blow-up and I completly destroyed a pack with the Tilde when it got behind me and I lost it and it full power dived into the concrete! There were dented and busted batteries everywhere but NO FIRE! You kids can take all the chances you want!
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Old Aug 06, 2003, 04:25 PM
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Walled Lake, MI, USA
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>> The organic materials and the Al foil will burn.
From Kokam MSDS - "If heated above 130C, Cell(s) may explode/swell or leak."

Thanks, Hoppy. I guess my question is a little more involved than that, as there are different levels of burning. For instance, burning phosphorus is a lot different from burning paper. What I'm really wonder is whether a LiPo cell heated above 130C would burn more like paper or more like phosphorus. In other words, is there a major chemical-type fire with intense heat, or a simple organic fire that quickly burns out. Obviously, either one could light nearby combustibles. But one type could cause more damage more quickly than the other. Also, I'm really surprised at the use of the word "explode" in the Kokam MSDS. I find it hard to imagine a soft LiPo bag "exploding" like a hard shell Li-ion cell unless there is a violent chemical reaction potential in LiPos that has yet to be fully acknowledged.

>> My NiMH's don't puff and I have never had one blow-up and I completly destroyed a pack with the Tilde when it got behind me and I lost it and it full power dived into the concrete! There were dented and busted batteries everywhere but NO FIRE!

So, Boomer, you would have absolutely no compunction about picking up a wrecked aircraft with a NiMH pack, tossing it into the backseat of your car and walking away? You don't think a NiMH (or NiCd) pack could be damaged in such a way that it could develop a delayed short, melt down in the back seat of your car and set the upholstery on fire? Most of the time you'd be right, whether you were using LiPo, NiMH or NiCd. Statistically, only a small percentage of e-flyers ever experience a battery-induced fire. That doesn't mean it couldn't happen to you. It only means that the odds are small that it will happen to any given individual.
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Old Aug 06, 2003, 04:40 PM
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Most gas and turbine fliers I fly with carry fire extinguishers....maybe "we" should too...
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Old Aug 06, 2003, 05:02 PM
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Zebulon, NC
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Quote:
Originally posted by boomerace
Not really I got rid of mine after I puffed one!
Why did it puff?
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Old Aug 06, 2003, 06:25 PM
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My NiMH pack blew up.

I still use NIMHs as well.
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Old Aug 06, 2003, 06:35 PM
Been There! Done That!
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Eugene, Oregon, United States
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Dave, I'm sorry but I'm not that stupid! The destroyed pack stayed on the concrete until the next day! Cue, the speed control shorted out and it puffed before I could get it disconnected! I have had that happen to NiMH's as well but they just got hot! This argument (discussion) has no logical ending so I'm out O here!
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Old Aug 06, 2003, 06:46 PM
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United States, CA, San Diego
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Quote:
Originally posted by rtideas
My NiMH pack blew up.

I still use NIMHs as well.
Looks more like the end was ripped off by the same force that pulled the spot welds free from the cell next door.

Steve
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Old Aug 06, 2003, 07:32 PM
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A NiCad Story....

I was fast charging an 8 cell AA pack a few years back,in my RC car racing days.It was a transmitter pack.Sitting on top of the charger,in my kitchen.I had done this many times,and knew all the science about nicad to be known to the rc'er back then.My brother was visiting,and standing on the other side of the room when we heard what sounded like a gunshot.In the next instant,my brother realized that something hit him square in the left glute. We thought he had been shot!Turned out to be the outer casing,the ENTIRE casing of one cell had been expelled from the pack at ballistic speed.This is what hit my brother in the backside.The moral of this story is,ALL energy storage devices have dangers to them.Be careful out there.
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Old Aug 06, 2003, 07:35 PM
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The button cap was blown off, ripping the welded tab with it across the parking lot--glad my head or other body part was not in the way. My ear rang for well over an hour.

Since it was in my hand and about 2 feet from my face, I was glad the cap blew off and not the whole cell out.

Be aware of the dangers of all batteries. And then use them wisely.

rt
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Old Aug 06, 2003, 07:53 PM
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Walled Lake, MI, USA
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>> This argument (discussion) has no logical ending so I'm out O here!

Very un-Boomer-like! But as those who are sticking around know, there is a logical ending to this discussion. All energy-storing mediums have the potential to self-destruct and cause damage. Only the failure modes differ. Discussing the various failure modes and putting them into perspective can only be a good thing. Thus the logical ending to this discussion will come when everyone has had a chance to provide their input, consider the input of others and, hopefully, leave this thread a little wiser and not upset with what someone else has said.
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Old Aug 06, 2003, 08:01 PM
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Space Coast
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Dave,
In regards to "how hot", try to set a hardwood floor on fire...it's hard to do, but it has been reported that a LiPo fire was hot enough to start wood burning, hot enough to start car uphostery burning and hot enough to burn formica. Seems 'pretty hot' to state it in technical terms.

Why are you surprised that the word explode was in the MSDS? Most LiPo manufacturers use the terms ignite, explode, get hot, cause serious injury. One would assume that is why they have those overcharge/overdischarge current/voltage limiters on LiPo powered commercial devices such as the cellphone you hold to your ear. I don't think you'll find that circuitry on NiMH/NiCd powered devices. Why not?

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Old Aug 06, 2003, 08:26 PM
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Hoppy, we've been through this same discussion in all the other LiPo safety threads. There have been no verified instances reported on this forum of a lithium polymer cell "exploding." Li-ion cells, yes; Li-poly cells, no. A recent discussion of an "exploding Li-poly" cell turned out in actuality to be a Li-ion cell. In fact, that's the one that scorched the wood floor in a gymnasium. Li-poly cells have been reported to puff up, overheat and catch fire, but not "explode." Now perhaps it is technically possible for a Li-poly cell to explode. If so, I'd like to know the technicalities of how an explosion can take place when the lithium polymer core is contained in a soft, thin plastic "bag." The point here is to understand the safety issues better so that we can better deal with them. Understanding begins with asking good questions and getting good answers.

By the way, I started a thread in Open Discussion called What Started the Fire to solicit experiences where fires were started by NiCd and NiMH cells. It seems that in every thread discussing Li-poly fires, someone makes a statement that you don't have those kinds of problems with NiCd and NiMH. My new thread has already generated 9 NiCd/NiMH fire stories in just 3 hours. I thought it would be appropriate to collect all of the NiCd and NiMH fire stories together in one thread so that a link to that thread could be inserted in every Li-poly fire thread just to provide a little perspective.

http://www.rcgroups.com/forums/showt...hreadid=139977
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