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Old Jun 08, 2004, 01:48 PM
Lagopus lagopus
WillowPtarmigan's Avatar
Houston Hobby, Texas, United States
Joined Jul 2003
765 Posts
What Causes LiPos To Explode?

Out of curiousity, why do LiPos sometimes explode? Are any companies trying to work on the problem, so they can improve LiPos and make them not explode? I know overcharging them will cause them to burst in flames.
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Old Jun 08, 2004, 02:21 PM
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vintage1's Avatar
East Anglia, UK
Joined Sep 2002
29,703 Posts
Pressure.
What causes the pressure? Gas coming of the electolyte.

What causes the gas? Too much current through the electrolyte, or xcharhgiong it past full, causing it instead of just conducting, to electrolyse - i.e. generate gases from whatever it is.

In the case of e.g.a lead acid battery, the water gets electrolysed to hydrogen and oxygen.

I am not sure what gases are prduced by LIPOS.

What the gas does is expand and puff and then pop the pack.


This is not in itself a p[roblem, but an expanded pack has lost electrolyte and put gas, instead of electrlyre, un contact wuith eth anodes and cathode.

Net effect is capacity and current handling is exremely reduced. Use that cell in a pack of otherwise un puffed cells, and its almost certain to over discharge, and over charge.

Then the pack will gas more, dry out, get hot and ultimately catch fire.

Then a safe failure mode (popped pack) becomes a LIPO fire.

Swollen paths are the first sign that a cell has gone bad. Use it and you risk the whole pack in flames.
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Old Jun 08, 2004, 02:49 PM
Electric Flyer
Connecticut, USA
Joined Oct 2003
430 Posts
Will.

According to Kokam, Kokam SLPB batteries will not explode even if punctured thru. They are made to gas out safely. Now, with that said, we go to the next dangerous phase. They will, if shorted, and having the right amount of resistance, heat up hot enough to catch fire, or catch surrounding items on fire.
I think if you charge them in a safe area, outside the aircraft, then place them back in, you will be just fine. Heck, the carriers ship them all over the place in plastic bags. (I'm not treating this lightly...if puffed...discard them)

Check Kokam here...
http://www.kokamusa.com/Overview.htm

Dick
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Old Jun 08, 2004, 05:22 PM
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Walled Lake, MI, USA
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We could repeat the semantics debate about whether they "explode" or "vent with flame."
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Old Jun 08, 2004, 05:43 PM
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Chicago
Joined Feb 2003
5,924 Posts
Exactly, hard case Li-ions do not explode either, they just do a "rapid-disassembly"
What makes lipos dangerous is fires. Rupture of that plastic pouch would be harmless i think.
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Old Jun 09, 2004, 11:06 PM
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Arkansas
Joined May 2003
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Where I used to work, we would say our batteries "vented violently".

Some were more like venting with flame, some made shrapnel.
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Old Jun 10, 2004, 01:15 AM
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Quote:
Originally Posted by vintage1
...electolyte...xcharhgiong...electrolyse...electr olysed...prduced...p[roblem...electrlyre...un...wuith eth...exremely...
Don't tell me I missed the inscription for the spelling mistake contest

Just kidding lol
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Old Jun 10, 2004, 08:06 AM
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Walled Lake, MI, USA
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Making shrapnel qualifies as an explosion to me. If the cell's outer shell does not come apart, but flame shoots out of a safety relief vent in an Li-ion or small holes in the side of a Li-poly, that's venting with flame to me.
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Old Jun 10, 2004, 09:45 AM
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hoppy's Avatar
Space Coast
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Quote:
Originally Posted by ch2s
Don't tell me I missed the inscription for the spelling mistake contest

Just kidding lol
INSCRIPTION, n. Something written on another thing. Inscriptions are
of many kinds, but mostly memorial, intended to commemorate the fame
of some illustrious person and hand down to distant ages the record of
his services and virtues.

hppy
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