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Old Dec 21, 2011, 09:33 PM
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Just talked with a friend who has been using lipos for years. Charging it on a plastic table in his garage with a four port charger and $2000 worth of gear. Lost it all.

Familiarity breeds contempt.
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Old Dec 21, 2011, 11:27 PM
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Originally Posted by Rickflaguy View Post
Just talked with a friend who has been using lipos for years. Charging it on a plastic table in his garage with a four port charger and $2000 worth of gear. Lost it all.

Familiarity breeds contempt.
Very true.
Any details? Didn't see it in the local paper but that's not unusual.
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Old Dec 22, 2011, 08:04 AM
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Good video bzfrank. It makes me laugh when people think they're safe and sound by simply being in attendance while charging. Assuming you're sitting right beside your charging LIPO's and watching them the whole time and wearing your fireproof suit and gas mask, you might be able to get it outside in time to avoid 20% of the toxic smoke in the house.
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Old Dec 22, 2011, 08:51 AM
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Good video bzfrank. It makes me laugh when people think they're safe and sound by simply being in attendance while charging. Assuming you're sitting right beside your charging LIPO's and watching them the whole time.
Actually people watching batteries charging are quite safe IMO. What you didn't see in the picture is the usually long time period between the application of overvoltage and the eventual ignition. The Utah Flyers reported that it took between 4-7 minutes for there overcurrent/overvoltage ignitions to occur. Lipos just don't go from normal to a flaming inferno in microseconds, it goes through several stages, the most notable being the ballooning of the pack which is very obvious to a "watcher" at which time the charging can be stopped and the battery safely disposed of.


Perhaps bzfrank would like to comment on what happened between starting the test and the ignition in terms of time and physical changes that occurred.
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Old Dec 22, 2011, 12:22 PM
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>> It makes me laugh when people think they're safe and sound

the reason is that fires tend to grow exponentially. If you react immediately, you will be able to handle it. If you are out of the room for a minute, by the time you're back the curtains will be on fire and all you can do is run.
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Old Dec 22, 2011, 01:34 PM
4.2V of pure Kraut power
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Perhaps bzfrank would like to comment on what happened between starting the test and the ignition in terms of time and physical changes that occurred.
Actually not very much. The temperature did start to rise steadily after 4.6V/cell was reached and slight puffing occurred over 4.8V/cell. However quite late in the process. The charge current did drop from 6A to 200mA in the last minutes as the internal resistance increased due to the decomposition of the electrolyte and cathode - Thermal runaway was well underway then and even if you would have disconnected the cell it still would have blown.

So if the cell already reached >80 degree celsius (180F) it will very likely go up in flames regardless of what you do or disconnect. The only safe handling is to put it in a place where it cannot start a fire and the toxic smoke cannot damage your lungs (contains hydrofluoric acid) and move out of the way fast. BTW flame length in my test reached more than 3 ft.

Regarding time: About 25 minutes from a fully charged 4.2V/Cell to the start of the fire. More than I thought it would. But it would not count that its always this long, it certainly depends on the make of the cell.
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Old Dec 22, 2011, 01:49 PM
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Last two years I've had my lipos and cells kicking it in my basement just chilling out. I have been meaning, more recently, to do something about that and I think I will finally put them at the least in some fireproof safe or similar.

The odds of a lipo fire ARE fairly small, otherwise we'd all be hearing regularly about fires, but they are not minute, and certainly the chances of house fire are increased if you're storing these things in the house, plus many of us have had crashes and have bent cells or whatever.

I did buy a fire extinguisher a while back and it is within easy reach.

Closest I ever came to a fire was a couple years back very stupidly and totally out of character for me (since when I do this I always set my watch count-down timer to remind me) I came down one day and realized the soldering iron had been put back on the shelf _plugged in_. It had melted a bunch of plastic and some netting but thank God nothing flamed up.
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Old Dec 22, 2011, 02:28 PM
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Last two years I've had my lipos and cells kicking it in my basement just chilling out. I have been meaning, more recently, to do something about that and I think I will finally put them at the least in some fireproof safe or similar.

The odds of a lipo fire ARE fairly small, otherwise we'd all be hearing regularly about fires, but they are not minute, and certainly the chances of house fire are increased if you're storing these things in the house, plus many of us have had crashes and have bent cells or whatever.

I did buy a fire extinguisher a while back and it is within easy reach.

Closest I ever came to a fire was a couple years back very stupidly and totally out of character for me (since when I do this I always set my watch count-down timer to remind me) I came down one day and realized the soldering iron had been put back on the shelf _plugged in_. It had melted a bunch of plastic and some netting but thank God nothing flamed up.
Heh... I cant tell you the number of times I have picked up a soldering iron by the wrong end
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Old Dec 22, 2011, 07:58 PM
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Very true.
Any details? Didn't see it in the local paper but that's not unusual.
Just took out some gear. No structural issues. Knowing him he dealt with it. Amazing kind man. He took my Park 400 with a ripped lead so short you couldn't get them to touch much less solder. He built a bridge of solder and called me to pick it up. do you want to fly at KMS with us?
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Old Dec 23, 2011, 12:27 PM View Post
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Old Dec 23, 2011, 01:54 PM
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wonderful christmas gift, they are a lot of small gifts on the battery, you do not miss this opportunity.

We are 30 per cent discount, take a look at our discount arrangements and products. Time is running out.http://yi.si/167
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Old Dec 23, 2011, 09:45 PM
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I popped a cell today

Yulp. I always say to S L O W L Y discharge an old lipo before tossing it away. I was in a rush to discard close to 20 packs today so I had a bunch of light bulbs connected to one pack at a time as I worked in the shop on other projects.
My wife came out and we were talking and POP . What the???? There was a bunch of debris spread around the lipo I was discharging.
One cell had gotten so much pressure that it popped. Some may argue that it exploded but to me an explosion would have been coupled with fire; this was not.
So, always remember, when discharging a pack to zero, do it S L O W L Y.

Anyhow, here is a couple pictures I took. First one was the one that popped, the second one was the next pack venting.

Rick
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Old Dec 23, 2011, 10:30 PM
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Originally Posted by rampman View Post
Yulp. I always say to S L O W L Y discharge an old lipo before tossing it away. I was in a rush to discard close to 20 packs today so I had a bunch of light bulbs connected to one pack at a time as I worked in the shop on other projects.
My wife came out and we were talking and POP . What the???? There was a bunch of debris spread around the lipo I was discharging.
One cell had gotten so much pressure that it popped. Some may argue that it exploded but to me an explosion would have been coupled with fire; this was not.
So, always remember, when discharging a pack to zero, do it S L O W L Y.

Anyhow, here is a couple pictures I took. First one was the one that popped, the second one was the next pack venting.

Rick

Yulp, I’m scared to asked. . . . .
“SLOWLY discharge an old lipo” “On a good pack this strip will discharge at >32 amps. WHOOPPPIIIEEEEE”
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Old Dec 26, 2011, 09:19 PM
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Originally Posted by rampman View Post
Yulp. I always say to S L O W L Y discharge an old lipo before tossing it away. I was in a rush to discard close to 20 packs today so I had a bunch of light bulbs connected to one pack at a time as I worked in the shop on other projects.
My wife came out and we were talking and POP . What the???? There was a bunch of debris spread around the lipo I was discharging.
One cell had gotten so much pressure that it popped. Some may argue that it exploded but to me an explosion would have been coupled with fire; this was not.
So, always remember, when discharging a pack to zero, do it S L O W L Y.

Anyhow, here is a couple pictures I took. First one was the one that popped, the second one was the next pack venting.

Rick
The definition of an explosion is the release of built up gas pressure. The best way to do that is with the conversion of a solid or liquid into a gas. Fire works well. Try pool acid and aluminum in a 2 liter bottle and you have a dangerous explosion with no fire. BURN GUNPOWDER IN THE OPEN AND YOU HAVE A RELATIVELY SLOW FIRE. Put it in a chamber and you have an explosion. C4 was used by special forces for heating food. You did have an explosion.
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Old Dec 27, 2011, 05:32 PM
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erm...
When dealing with gunpowder etc, you draw the line between deflagration and detonation. The latter is when the process propagages through the shock wave. Also on the Wikipedia page for "explosion", the words "shock wave" and "extreme manner" appear in the first paragraph.

All this has no connection whatsoever with LiPos. There is no shock wave, no rapid propagation of a flame front etc. I don't think mixing gunpowder and LiPos as an example will help anybody. They have very little in common.

Well, if the LiPo goes "pop" and you don't call it an "explosion", you'll have at least my vote for sure.
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