Electronics > Projects, Designs, and Technical Stuff
Deliberate Lithium cell overcharging
ogden:
--- Quote from: Siwastaja on May 12, 2019, 08:40:42 am ---Your point is quite moot, as there is no metal lithium in a lithium ion cell, in a similar way that there is no metal sodium in your table salt: they react similarly with water: nothing happens.
Similarly, chlorine gas is extremely poisonous, yet NaCl doesn't easily decompose into it.
Chemistry can be unintuitive for a layperson. But for the exact same reason Li or Na is so freaking reactive, it's also extremely unreactive going back to the opposite direction. In a li-ion cell, it's in the "reacted" or unreactive form, the same as in your table salt. In metal lithium primary cell, it's in the reactive metal form.
--- End quote ---
Well, well... If contents of Li-Ion battery is so "unreactive" with water, then how you explain following video?
https://youtu.be/cTJh_bzI0QQ?t=483
Siwastaja:
--- Quote from: ogden on May 12, 2019, 08:55:12 am ---Well, well... If contents of Li-Ion battery is so "unreactive" with water, then how you explain following video?
https://youtu.be/cTJh_bzI0QQ?t=483
--- End quote ---
The answer is in the title: it's a lithium (nonchargeable, primary) battery, which has absolutely nothing to do with lithium ion battery (secondary, chargeable cell).
Primary lithium cells contain lithium (metal), which burns when reacting with water, as seen in the video. Li-ion cells do not normally contain meaningful amounts of lithium metal.
Primary lithium cells are typically very small, and indeed non-rechargeable, typically used to power real-time clocks, etc, or small gadgets, smoke detectors, remote controls, etc., as alternatives for traditional alkaline cells.
Rechargeable packs are always li-ion, so in practice it should be easy to know which one you are facing. Li-ion is also getting really ubiquitous really fast, with an almost alarming growth rate, so, even though the safety is getting better, we are bound to see some li-ion fires, and hence need to understand the right fire-fighting strategy, which is using a lot of water, for a long time, to cool the battery pack internally. Firefighters are being educated and probably mostly know this, but it doesn't hurt to know for laymen, either.
The "lithium burns if you fight li-ion fire with water" myth is extremely dangerous and really needs to die, finally.
Now, I do see that people colloquially talk about "lithium batteries" when talking about li-ion packs. In this case, you need to guess what they mean. If they are talking about a rechargeable pack, or a large battery, there's not much choice here, it's li-ion. You can try to correct them, but people will continue talking about "lithium batteries" - including many official documents as well.
Finally, as a terminology reminder, LiPo or "lithium polymer" is exact same thing as lithium ion, just an alternative marketing term typically used for pouch form factor li-ion cells. I feel this is an important addition here as the words "lithium polymer" omit the word "ion", possibly misleadingly. (I have seen people think that LiPo cells are rechargeable metal lithium batteries, which of course isn't true.)
tszaboo:
--- Quote from: Siwastaja on May 12, 2019, 08:56:50 am ---
--- Quote from: ogden on May 12, 2019, 08:55:12 am ---Well, well... If contents of Li-Ion battery is so "unreactive" with water, then how you explain following video?
https://youtu.be/cTJh_bzI0QQ?t=483
--- End quote ---
The answer is in the title: it's a lithium (nonchargeable, primary) battery, which has absolutely nothing to do with lithium ion battery (secondary, chargeable cell).
Primary lithium cells contain lithium (metal), which burns when reacting with water, as seen in the video. Li-ion cells do not normally contain meaningful amounts of lithium metal.
Primary lithium cells are typically very small, and indeed non-rechargeable, typically used to power real-time clocks, etc, or small gadgets, smoke detectors, remote controls, etc., as alternatives for traditional alkaline cells.
Rechargeable packs are always li-ion, so in practice it should be easy to know which one you are facing. Li-ion is also getting really ubiquitous really fast, with an almost alarming growth rate, so, even though the safety is getting better, we are bound to see some li-ion fires, and hence need to understand the right fire-fighting strategy, which is using a lot of water, for a long time, to cool the battery pack internally. Firefighters are being educated and probably mostly know this, but it doesn't hurt to know for laymen, either.
The "lithium burns if you fight li-ion fire with water" myth is extremely dangerous and really needs to die, finally.
Now, I do see that people colloquially talk about "lithium batteries" when talking about li-ion packs. In this case, you need to guess what they mean. If they are talking about a rechargeable pack, or a large battery, there's not much choice here, it's li-ion. You can try to correct them, but people will continue talking about "lithium batteries" - including many official documents as well.
Finally, as a terminology reminder, LiPo or "lithium polymer" is exact same thing as lithium ion, just an alternative marketing term typically used for pouch form factor li-ion cells. I feel this is an important addition here as the words "lithium polymer" omit the word "ion", possibly misleadingly. (I have seen people think that LiPo cells are rechargeable metal lithium batteries, which of course isn't true.)
--- End quote ---
Except it is not a myth. There were several electric cars on fire, and the firefighters used water to extinguish it, only to have it on fire again later. I dont know what is wrong with you, going against facts, just because you think that reality doesn't work that way.
https://piximus.net/vehicles/this-how-dutch-firefighters-put-out-the-fire-of-bmw-i8
"The fire department and BMW employees were able to move the vehicle outside, where normal techniques failed to extinguish the battery pack, which they found difficult to reach,"
https://www.total-croatia-news.com/made-in-croatia/23852-the-grand-tour-season-two-episode-one-is-out-and-rimac-concept-one-is-on-flames
"May told us the story of how Rimac Concept_One kept catching fire for 5 days after the crash"
https://www.theverge.com/2018/6/26/17507254/tesla-crash-battery-fire-florida-ntsb
"They extinguished it using as much as 300 gallons of water and foam."
"As the car was being loaded for removal from the scene, the battery reignited and was quickly extinguished."
So yeah, they tried water, lots of water, and it doesnt work, probably it made everything worse.
beanflying:
As someone who has crashed and seen crashed a lot of Lithium powered aircraft and helis it is actually very difficult to get one to combust and get to flames. The more normal mode post impact is smoke, heat and puffing of the packs and not flame.
Post impact risk minimisation is as important as the threat remains after impact of those damaged cells. Having some method to reduce heat in a damaged pack is as important as anything to prevent a fire.
Marco:
I wonder if electric cars are designed to let water easily penetrate all of the battery once a fire has started, they probably should.
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