Not in my pocket, thank you !
......... “we tried to simulate a range of abuse conditions, from moderate temperatures up to trying to simulate a fire. And who wouldn't love to have the chance to try and reproduce that experiment"........?
UK boffins have taken a close-up of what happens with Li-ion batteries when they get hot under the collar, and it's not pretty. As Lenovo, Boeing, Tesla, Sony and others will attest, Li-ion battery fire-safety is worth researching. However, the University College London boffins say most analysis of battery fires has focussed …
This is really fascinating, in a "Seconds from Disaster" documentary sort of way.
But I always wondered what happens when a LiPo decides to go into full on Chernoshima meltdown, having had one do that while charging before.
I did have a theory a while back that some Li-ion fires are actually caused by microscopic Li-Al dendrites from the current collectors formed over hundreds of charge cycles, the early Li metal cells were prone to Li dendrites but switching to a ion only system has mitigated the threat substantially.
It has also been linked to tin pest as the mechanisms are remarkably similar and in fact tin contamination of the Al collector might be a possible cause of spontaneous runaway.
Incidentally this is why Li-MnO2 and Li-FeS2 can't be recharged because this happens even if the cell is recharged at 0 celsius.
It might work once for a slightly depleted cell but you are playing with fire here and it simply isn't worth it for something that only costs £2.25 a cell in the first place.
When overcharged or overdischarged, the li-ion cell starts dissolving its copper, and producing metallic lithium. When the dissolved copper precipitates again, there's no telling where it ends up. If a shunt forms, it might cause localized heating and set off thermal runaway. As for metallic lithium, needless to say, it's highly volatile. The damage is accumulating.
RC Hobby people get relatively frequent battery fires, a consequence of running batteries without protection circuitry, and running batteries hard, making their base temperature already high, before builtin or evolved defects come into play.
LMAO!
One thing I did notice is that small <300mAh LiPo cells which are questionable often exhibit a "two step" discharge profile which suggests an intermittent internal connection.
Upon storing for a while they invariably puff up so it might be worth checking this for the folks using LiPo on models.
I did wonder if the problem on some of these is the same as the crimp FAIL on Li-FePO4 cells made by A123, perhaps the machine they used has the same problem?
Its a pressure crimp so if the die was slightly off centre smaller cells would be more prone to this and in fact a "partially good" cell might later fail due to electromigration of aluminium in the interconnects.
Its also worth mentioning that I've taken apart a fair number of cells and noticed this for myself, especially on the model heli packs.
Sometimes the crimp fails before the cell is fully open, actually falls off the Al leaving a divot in its place like a bad spot weld.
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> Well, I thought this video was very dull. No bangs, no flames; just a couple of spotty youths saying that maybe by studying batteries they could "make them safer". Yawn.
Yes, surprisingly lacking in anything informative.
So what were their conclusions exactly?
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More energy = more danger. I learned that *years ago* when a "dead" alkaline PP3 was short circuited by coins in my pocket. Didn't quite blister but it certainly energized ME.
http://en.wikipedia.org/wiki/Nine-volt_battery
The power density of batteries is slowly catching up on gunpowder. When I built (ca 1956) an electromagnetic ball-bearing launcher, this 12 year old's version of a not yet invented "railgun", in my bedroom, I could have sent them THROUGH the wall -- if I'd used a (not invented yet) LiFePO battery instead of a Lionel train transformer.