Deliberate Lithium cell overcharging - Page 1
Forum section: electronics / projects

author: ThinkingGrenade
author_rank: Newbie
timestamp: May 10, 2019, 05:12:11 pm
content: I need to produce a overcharge condition in some typical 18650 cells (and large Lipo's) for training with our local fire and rescue service. i can pop 1 or 2 18650's with my bench power supply, but i need to do it with 8/10 (or more) cells at the same time.- a quick background - I live on the Isle of Man, every year the TT races are held here (google it) and for the last few we have had a race dedicated to Electric bikes (they aint slow) - some of which use a huge bank of 18650's. there was a fire last year that involved one of these packs, and the Fire service want to do some training with some new fire fighting mediums, specifically designed for battery fires)I work for a company that provides fire equipment and i know how to make most things go boom, but im asking you guys, as my experience is limited with this kind of thing......

author: NiHaoMike
author_rank: Super Contributor
timestamp: May 10, 2019, 05:48:16 pm
content: Connect them all in parallel with a welder. Shouldn't take too long to get some flames.

author: AG6QR
author_rank: Frequent Contributor
timestamp: May 10, 2019, 05:49:57 pm
content: It's not my area of expertise, but it sure sounds like fun!My naive approach would be to first charge them fully with a proper charger to fill them with as much energy as practical. Then, put three in series, and put them on a big charger intended for car batteries. If you want to make more go off, wire up multiple parallel combinations of three in series.Of course take appropriate safety precautions by keeping them far from humans and far from combustibles.And have the cameras running!

author: MagicSmoker
author_rank: Super Contributor
timestamp: May 10, 2019, 06:08:32 pm
content: Overdischarge until at least one cell experiences voltage reversal reliably damages all lithium chemistries, but the real fireworks mainly occur during subsequent charging, particularly at currents >1C (e.g. - >4A for a 4Ah cell). However, the LiFePO4 is particularly tolerant of abuse and can take 4C charging in stride so wouldn't be the best choice if you actually want something bad to happen. Any of the Cobalt-containing chemistries should give you the kind of surprise you're looking for, but do make sure you have a blast shield of some sort if using 18650 or larger cells.

author: KC0PPH
author_rank: Unknown
timestamp: May 10, 2019, 06:13:33 pm
content: Go buy an EDF RC airplane that runs off of 6S batteries. Fly the piss out of it for a few days fast charging each time, they should start puffing up pretty quickly (keep throttle wide open). Once they are puffed nicely then put them on a bench supply and charge with as fast of current as you can give em. They will make a spectacular show.Batteries that are new tend to not be as entertaining to blow up, however well used ones with high IR tend to be exciting.

author: Berni
author_rank: Super Contributor
timestamp: May 10, 2019, 06:14:22 pm
content: Yep stick it across a big DC welder and off it goesIt's not even nececerry to overcharge the whole pack. These big battery pack fires are often started by a few bad cells. Once it starts going the batteries produce enough heat to cause the ones around it to explode and kick off a chain reaction that sets the whole pack on fire.Another way to make them explode is to simply hammer a nail into the side of a cell.But do take care because these cells can explode violently enough to launch them pretty far. Wouldn't want one flying off out of the training zone and setting something else on fire.Id say a 20m safety radius around the battery is a minimum.

author: ThinkingGrenade
author_rank: Newbie
timestamp: May 10, 2019, 08:37:28 pm
content: Cheers folks.Quote from: Berni on May 10, 2019, 06:14:22 pmthe few cells in the middle was the approach i was going to use, the hammer is the tertiary back up plan after the secondary blowtorch on a stick.all this is going to be done at an actual fire training facility, with guys in full kit. ill be wearing a polo shirt/high vis vest and squinting heavily. i have had experience with explodinating 7 and 8 cell lipo's and a few 18650/20700's so i personally know how violent they can bewelder accross the pack seems to be the way to do it. my next thought would be to use a couple of 12v car batteries.Quote from: MagicSmoker on May 10, 2019, 06:08:32 pmoverdischarge might also be the way to go. i can easily achieve that too. im gonna have a test and just short them to see how well it works.I promise to film as much as i can of this BTW.

author: MosherIV
author_rank: Super Contributor
timestamp: May 10, 2019, 10:50:45 pm
content: HiI work for a company designing and building lion packs for automotive.One of the tests that must be done is to test what hapoens if one cell gasses and ignites.To force a cell to ignite I was told that you just heat it gently.It will eventually gas and ignite.Hope that helps.

author: amyk
author_rank: Super Contributor
timestamp: May 10, 2019, 11:42:44 pm
content: How about a simpler option: straight across the mains.18650s, especially the newer ones, are surprisingly tame when only "moderately" overcharged, since the safety standards require them to pass such tests:Quote(Fromhttp://dalincom.ru/datasheet/SAMSUNG%20INR18650-25R.pdf)You may get better "bang for your buck" with pouch cells, or if you insist on 18650, the cheapest ones from Aliexpress with "fire" in their name...

author: Rerouter
author_rank: Super Contributor
timestamp: May 11, 2019, 01:44:08 am
content: If you want a proper hard to control fire, its either going to be a hard short with a non-tolerant chemistry, or for maximum effect excessive overcurrent to a higher voltage,LiFe is too stable and wont be used in applications where every bit of power to weight matters, Li-Ion / Li-Poly (same thing in effect) will be used, but the li-poly pouches rarely have the over pressure disconnect that the 18650 cells have. If you do want to fail 18650's you need to heat them up to a destructive temperature before the gas pressure can build up, so the reaction continuesSo take say an unprotected 3S pack with as many in parallel as you like, and hook it in parrellel to a truck battery with some jumper leads (truck side last to give you room to run), it should flame up in the next few minutes.

author: 3roomlab
author_rank: Frequent Contributor
timestamp: May 11, 2019, 01:58:30 am
content: I happen to have read thisthis DoD experiment, they made a fake cell which is a control cell with a heater inside used to heat a group of cellsmaybe in your case, overheat to ignition. and it maynot even need to be a cell, just a heaterhttps://digitalcommons.unl.edu/cgi/viewcontent.cgi?referer=&httpsredir=1&article=1105&context=usnavyresearchNovel 18650 lithium-ion battery surrogate cell design with anisot.pdf(over 2mb doesnt upload in post)

author: Siwastaja
author_rank: Super Contributor
timestamp: May 11, 2019, 02:21:25 pm
content: Proper 18650's tend to be fairly well protected with integrated PTC and CID devices. For demonstration, I have tried:* Dead-shorting 18650's,* Charging 18650 cells from a 30V, 10A lab supply, forhours-and haven't been able to cause fire, explosion, smoke, or significant venting of electrolyte. Sony cell on a 30V,10A supply worked as a hysteretic PTC thermostat controlled heater, stabilized at around 100 degC IIRC.Manufacturers oftenspecifysuch test cases and guarantee* no fire. (* or, at least, that "no fire" is atypicalresult.)For reliable demonstration, I'd suggest sourcing some low-quality cells (think about UltraFire etc. brands), and testing thoroughly before the big day.Physical nail penetration might be the best, if it needs to demonstrate a typical cause. Otherwise, +1 for the in-battery cartridge heater! PTCs, CIDs etc. can protect againstinternalheat generation over the thermal runaway onset temperature, but using an external source, there's no limit. You should see things start going after your cells reach about 160 degC. (For LFP, that would be higher.)If it needs to be external and electrical, long-term overcharging (or forcing negative voltage) would have best chances. Shorting a cell is almost a guaranteed demonstration failure - only the very crappiest cells would cause a fire during an external short.Or, ramp up the voltage enough to arc through the PTC, CID and even the shutdown separator - a few hundred volts, maybe?It sucks trying to demonstrate a li-ion fire. The chemistry itselfisvolatile, but they have significant load of safety features; they need to have, many BMS ICs on the market have a long tradition of having some dangerous failure modes, so the cell manufacturers have learned their lessons, their safety process is not completely relying on the pack designer staying within ratings. Yet, abusing a celldefinitelyincreases the fire risk (which is why we do see fires related to, for example, overcharging after the management system failed), but not enough to provide a robust way to produce demonstrations easily (unless you are able to source a consistently very crappy cell).

author: Rerouter
author_rank: Super Contributor
timestamp: May 11, 2019, 02:28:48 pm
content: the 10A limit on your supply would probably be the limiting factor, you need to heat the contents to about 150C to cause the reaction to begin, I suppose for fire fighting test you could just use some nichrome wire to heat them up to this situation.

author: Yansi
author_rank: Super Contributor
timestamp: May 11, 2019, 02:29:52 pm
content: To fight lithium battery fires - use water. A LOT OF IT. The important thing is to cool them off as much as possible.

author: Siwastaja
author_rank: Super Contributor
timestamp: May 11, 2019, 02:35:13 pm
content: Quote from: Rerouter on May 11, 2019, 02:28:48 pmWell, I have tested direct connection to a 12V lead acid battery as well. The result was similar to dead-shorting the cell itself - with little current limiting resistance, resulting in massive currents (>> 100A), almost no heating happens, as the PTC just reacts so quickly. In the end, less damaging charge (I*t) might go through the cell, compared to the current-limited lab supply test case.I do agree that very large currents could cause localized heating within that short time, which could trigger thermal runaway, but I haven't been able to demonstrate that on brand cells, very likely because they use shutdown separators, melting and stopping ion transfer at the local hotspot before it can spread.For any particular cell, either a very high current, or a more modest overcurrent, might do the trick, but the chances are that neither will.External heating is indeed the only reliable way to start the thermal runaway.

author: Rerouter
author_rank: Super Contributor
timestamp: May 11, 2019, 02:44:26 pm
content: also to keep the water flowing well after the main event has settled down (can be low flow rate, water is very efficient at soaking up heat, and if its slow you may be able to see the steam if its about to reflare), when the batteries burst in to flame, generally there internal structure has been damaged enough to short out, so you initially extinguish the light show by cooling it down, but you need to maintain that cooling until every part of the pack is discharged,Once the fire is out, you want to remove it from the vehicle, and Ideally leave it in a puddle of fresh water or similar to make sure its cold, you ideally would also want something like jumper leads with a bulb to discharge the pack reasonably slowly, When the battery is at 0V on all cells, then and only then can you turn your back on it and call it safe.In a pinch Co2 extinguishers can chill packs quite quickly (dropping pressure on a gas causes a sub ambient cooling effect) however this is more for gaining time if your waiting on the water sources to come out.the main thing I would say to avoid at all costs is ABE/ABC style extinguishers, the active components are salts, so if you combine that with a recently hosed down wet pack you end up with pockets of highly corrosive brine which will happily eat through most battery casings over a few weeks / months, possibly causing later issues if not all of the pack was drained.

author: Yansi
author_rank: Super Contributor
timestamp: May 11, 2019, 05:37:23 pm
content: Quote from: Rerouter on May 11, 2019, 02:44:26 pmIn my personal experience, from an environment where rather large 5+ kWh packs were built, CO2 extinguishers are of not much use. Maybe only for small packs, but their cooling effect is very subtle and short-durating, compared to a full bucket of water.DO NOT rely on CO2 extinguishers when handling large battery assemblies!

author: amyk
author_rank: Super Contributor
timestamp: May 11, 2019, 06:54:21 pm
content: Quote from: Siwastaja on May 11, 2019, 02:21:25 pmEven then, you might not get a fire. I can't find it now but there's a video on YouTube of someone driving a nail through a fully-charged 18650, and all it did was bubble electrolyte out, melt the wrapper, and then cool down boringly. I guess you need temperatures high enough to ignite the electrolyte in order to get anything more interesting to happen.

author: ogden
author_rank: Super Contributor
timestamp: May 11, 2019, 07:08:01 pm
content: Better train your firefighters properly. Internet search gave many hits regarding EV fire training. Just one:https://www.nfpa.org/Training-and-Events/By-topic/Alternative-Fuel-Vehicle-Safety-Training

author: Marco
author_rank: Super Contributor
timestamp: May 11, 2019, 07:19:22 pm
content: I don't see how reproducing the exact way it catches fire is important for extinguishing it, as long as it only burns on its own accord when you start.Wrap a cell in some magnesium ribbon to kick off the festivities?

author: james_s
author_rank: Super Contributor
timestamp: May 11, 2019, 08:05:22 pm
content: There's no need to abuse the cells prior, lithium battery fires occur when cells are overcharged, or when they short circuit internally which is also what happens when they are overcharged. Worn out or abused packs tend to be more vulnerable because they can get out of balance but it's the overcharging that makes them burn.That said, I don't really see what the point is here. The best way to fight a lithium battery fire is plain old fashioned water and lots of it. Take away the heat and the fire goes out.

author: Zero999
author_rank: Super Contributor
timestamp: May 11, 2019, 08:05:41 pm
content: Be careful. Lithium batteries are highly explosive. Photonicinduction did a couple of videos of them being abused.Poking one with a skewer causes an explostion.Fast forward to 6:00 for the lithium part. A small cell burns quite well when connected to AC.

author: james_s
author_rank: Super Contributor
timestamp: May 11, 2019, 09:32:44 pm
content: They are not "highly explosive", or even moderately explosive, they contain flammable materials and a lot of stored energy so they can burn vigorously. That is not an explosion, it is a fire.High explosives are things like nitroglycerine, dynamite, TNT, RDX, etc. No lithium battery behaves anything like this.

author: Zero999
author_rank: Super Contributor
timestamp: May 11, 2019, 09:53:37 pm
content: Quote from: james_s on May 11, 2019, 09:32:44 pmThe first video certainly does look like an explosion, rather than a fire, as there are no flames.Where it actually is an explosion or not, the effect is the same: a big bang, along with lots of heat is produced.

author: amyk
author_rank: Super Contributor
timestamp: May 12, 2019, 12:01:44 am
content: That was definitely not an explosion, there wasn't even a "big bang". If it was an explosion there would be a shockwave and shrapnel everywhere.

author: Siwastaja
author_rank: Super Contributor
timestamp: May 12, 2019, 07:16:49 am
content: Quote from: amyk on May 11, 2019, 06:54:21 pmIndeed - often the manufacturers even document a nail penetration test, with a typical result of "no fire".Nail penetration causes local internal short circuit, but if the shutdown separator works as intended, the ion transfer stops / is limited, limiting the temperature rise below the runaway onset temperature.Smaller cells tend to perform better because they are more isothermal, with safety layers reacting better to the average cell events (think about the PTC cap of a 18650, and compare it to a massive prismatic cell.)Note that it is dangerous torelyon all these cell-level protections; the risk is hugely increased when abusing cells, especially physically. However, the risk is still awkwardly small when your target is todemonstratea battery fire.To say it in other words with made-up but representative numbers, assume that a risk of li-ion fire, using high-quality cells, is, say, 1 failure per 10^6 packs. Now, overcharge the cells severely, and the risk might go up by 1000x, to 1 failure per 10^3 packs; a huge safety issue if you have epidemic BMS failures; but still low enough so it's almost impossible to demonstrate. I have seen so many overcharging events, and never a fire resulting. Have been lucky - or unlucky, depending on what you want to see.Re: explosion, this is a classical case of there being two completely different meanings for the same word: the scientifically defined exact meaning, and the colloquial meaning. I wouldn't make a big fuss about it, people do and will always call almost anything an "explosion" if itfeelslike it to them, and this isn't wrong, just how language works.

author: Zero999
author_rank: Super Contributor
timestamp: May 12, 2019, 07:48:35 am
content: Quote from: amyk on May 12, 2019, 12:01:44 amWhatever, perhaps you'll feel comfortable poking a lithium ion battery with a skewer, whist holding it in your hand.It's good they way the myth about water and lithium ion batteries is busted in that video, as it doesn't burst into flames, when wetted.

author: tszaboo
author_rank: Super Contributor
timestamp: May 12, 2019, 08:28:35 am
content: Quote from: james_s on May 11, 2019, 08:05:22 pmWell, yes and no. Sand is probably the best to put out the fire on the short term, and let it burn on your term later."Lithium reacts intensely with water, forming lithium hydroxide and highly flammable hydrogen. The colourless solution is highly alkalic. The exothermal reactions lasts longer than the reaction of sodium and water, which is directly below lithium in the periodic chart.2 Li(s) + 2 H2O -> 2 LiOH (aq) + H2(g)At 750oC lithium reacts with hydrogen to lithium hydride (LiH). The white powder that forms releases hydrogen gas upon later reaction with water, in amounts of 2800 liter per kilogram hydride. As such, lithium can be applied as hydrogen storage."So once the cell is damaged, it might catch on fire days after it has been put out, just because lithium reacting with water. Besides it emitting H2, which might explode, it could emit Hydrogen fluoride, which is poison.

author: Siwastaja
author_rank: Super Contributor
timestamp: May 12, 2019, 08:40:42 am
content: Quote from: NANDBlog on May 12, 2019, 08:28:35 amYour point is quite moot, as there is no (or very little) 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: seeing the same atom as in a well-known poison or dangerous substance doesn't necessarily mean anything (think about H2O, or many CN (cyanide) containing safe substances for example).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 Na is in your table salt. In metal lithium primary cell, it's in the reactive metal form.Although, there might be some corner cases where a long-time abused cell has developed small amounts of lithium metal (see: lithium plating, for example, during overcharge), which, even if, due to the minuscule amount, doesn't produce much energy when reacting with water, could, in certain conditions,triggeranother reaction. But I don't think this is very relevant in the big picture - the damaged cells are dangerous as long as there is significant stored chemical energy left in them, and the actual trigger can be anything. It's probably a false assumption that lithium-water reaction has anything to do with it.Feel free to store burned cells in sand after the initial fire has been taken care of with a lot of water, and the battery has been dismantled - probably a good idea. Sand is easy to obtain in large quantities, and provides good combination of thermal insulation and thermal capacity, withstanding high temperatures. During an incident, getting sand inside and around a pack is probably much more difficult and destructive to the surroundings, compared to simply pumping some water through a hose.

author: beanflying
author_rank: Super Contributor
timestamp: May 12, 2019, 08:55:08 am
content: There is one obvious suspect local (very suspect) who would love to help you build a device to overcharge some Lithium Batteries. I am sure Clive would be up for a build in some form and some video of it in use for your training.http://www.bigclive.com/https://www.youtube.com/user/bigclivedotcom/search?query=lithium

author: ogden
author_rank: Super Contributor
timestamp: May 12, 2019, 08:55:12 am
content: Quote from: Siwastaja on May 12, 2019, 08:40:42 amWell, 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

author: Siwastaja
author_rank: Super Contributor
timestamp: May 12, 2019, 08:56:50 am
content: Quote from: ogden on May 12, 2019, 08:55:12 amThe answer is in the title: it's alithium(nonchargeable, primary) battery, which has absolutely nothing to do with lithiumionbattery (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 gettingreallyubiquitous 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.)

author: tszaboo
author_rank: Super Contributor
timestamp: May 12, 2019, 10:33:02 am
content: Quote from: Siwastaja on May 12, 2019, 08:56:50 amExcept 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.

author: beanflying
author_rank: Super Contributor
timestamp: May 12, 2019, 10:52:29 am
content: 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.

author: Marco
author_rank: Super Contributor
timestamp: May 12, 2019, 11:06:21 am
content: I wonder if electric cars are designed to let water easily penetrate all of the battery once a fire has started, they probably should.

author: Siwastaja
author_rank: Super Contributor
timestamp: May 12, 2019, 12:00:52 pm
content: Quote from: NANDBlog on May 12, 2019, 10:33:02 amYou are mixing things up and making a wrong conclusion.It's completely true that it's hard to permanently extinguish a large li-ion pack fire, and it's fully true they easily reignite, but the conclusion that it's because lithium metal is reacting with water, is the wrong one. Your conclusion that fighting them with water somehow caused them to reignite is false, as well. They reignite because they are damaged and store the latent chemical energy and an oxidizer.It's just that water isn't capable of rendering the cells "safe" in one pass - this is true for all other ways to fight the fire as well. Your idea of burying the burned cells in sand is IMO a very good one, but in practice you would often need to fight the fire with water first, to prevent damage to surroundings. You'd be very lucky to have the fire happen in such controlled environment where you don't need to think about protecting the surroundings. And, stopping the pack fire is the most powerful way to protect the surroundings, you just need to understand it's still not safe after the fact.It has nothing to do with lithium reacting with water. Theactualreaction is the li-ion cathode intercalation breaking down: consider the most traditional LiCoO2 cathode. More modern NCA and NMC used in most EVs are similar. The issue is that the cathode itself supplies the oxygen, and the cathode stability is poor: it breaks down if enough Li is removed from the matrix due to overcharge, or if temperature exceeds the thermal runaway onset temperature, just around 160 degC for these cathode materials. (A bit more for LMO or LFP.) There is a lot of oxygen in this intercalation matrix, and thus a lot of potential chemical energy; this isthe unstablecomponent of the battery, not li metal, which doesn't exist there in large enough amounts to matter. Additionally, the flammable electrolyte (organic solvent such as a combination of ethylene carbonate and other similar substances) is not helping, and this is the typical source of shooting out flames you see.The issue is, because the battery has its own source of oxygen (and worse: in a fairly unstable form), it's hard to extinguish: the traditional way of removing air supply (CO2, powder, foam, etc. extinguishers) doesn't help at all; the fuel is there as well; the only way is to actively remove heat. But because the thermal runaway temperature is low, it reignites pretty easily unless actively cooled for indefinite time. Especially because now the cells are physically damaged.So, understanding the chemistry, it isn't surprising at all that the packs reignite; it's completely as expected. The firefighters need proper training to understand this: a pack doesn't become safe after it has been cooled down and the fire ceased. If this has come as a surprise for any fire brigade, IMHO the EV industry has failed to do their job of arranging proper training for this new tech.So, water indeed doesn't safely and fully conclude the case, you are right in that. Your problem is assuming that some other way would be better, or that water is adding to the problem.Water is the only practical way to quickly control the heat release during the incident (which is why it's the officially preferred method of fighting li-ion fire), but you absolutely must know how to do the aftermath. It's not a bad idea to let the cells burn in a controlled environment, that'll eventually release all the chemically stored energy. But, during a firefighting situation, this is often unacceptable - think about a on-board airplane fire as an extreme example. You need to transfer the pack to a safe place first. IMHO, EV manufacturers should take care of this safe aftermath business.AFAIK, water does not do any such extra damage causing cells to become "more dangerous". It's just that, even water is unable to solve the problem in "one go".If you look at the official firefighting recommendations, I recommend to look recent ones. The industry and the officials have reached the conclusion of recommending using a lot of water during the last decade or so. We are seeing an evolution here: first they recommended completely random things, not knowing about the chemistry (and li-ion fires were such rare occurences, and packs were small, so it didn't matter much). Then, they understood that you need to fight it with water; but the need for aftermath is still underestimated and poorly specified. I guess we'll see improvement there next.

author: nctnico
author_rank: Super Contributor
timestamp: May 12, 2019, 12:41:25 pm
content: Quote from: ThinkingGrenade on May 10, 2019, 05:12:11 pmHeat, overcharge or short. The last two will require to disable the BMS (circuit board) and fuse of the battery pack.The key to putting out a Li-ion pack which is on fire is to submerge it in water for a day so it can cool down completely. A fire in a battery pack is a chain reaction because the cells heat eachother and then ignite themselves heating up their neighbours. Dutch fire brigades are getting equiped with large (open) containers filled with water in which they can submerge electric vehicles. Needless to say the car is completely ruined (FUBAR) after that. Siwastaja is also involved in manufacturing Li-ion battery packs; he has given some good advice in his posts.

author: 3roomlab
author_rank: Frequent Contributor
timestamp: May 13, 2019, 06:42:54 am
content: @ Siwastajain post #10, the pdf decribes experiments done to determine the specific heat and internal thermal resistance of a cell (thru the folded layers). If I am understanding the numbers correctly, shouldnt it be more dangerous to make larger battery cells? as the inner temperature rise cannot be dissipated as quickly as smaller (or flatter with more surface area) cells?

author: beanflying
author_rank: Super Contributor
timestamp: May 13, 2019, 06:53:51 am
content: I the case of the OP it doesn't matter how the cells are made only how to manage them safely post impact or fire from X electrical failure causes. It would be a long way OT to get into Cell construction.If they are burning put them out and remove any chance of them reigniting (most likely chemically neutralised post extinguishing) or keeping them managed so they never get to a combustion point and can be moved safely for likely chemical treatment.

author: Siwastaja
author_rank: Super Contributor
timestamp: May 13, 2019, 07:04:03 am
content: Quote from: 3roomlab on May 13, 2019, 06:42:54 amYes, exactly. Actually I remember this being a marketing argument for Tesla's 18650 cell choice, back in the days they were still smaller and published more engineering argumentation for their technical decisions: a 18650 remains almost isothermal, and produces a large surface area to volume ratio, so that large packs can be actively forced to an even temperature, which will be good for both safety and even aging and little need for balancing.Quote from: beanflyingI'm not aware of any such neutralizing agent capable of preventing reignition (remember the cells have the internal oxidizing source), maybe I have missed something, dare to share more details?

author: beanflying
author_rank: Super Contributor
timestamp: May 13, 2019, 07:35:28 am
content: Section four in this PDF is fairly comprehensivehttp://hahana.soest.hawaii.edu/seagliders/manuals/electrochem_Battery_Safety.pdfAn expanded version of this sort of treatment is where I was heading with my previous post. It will make sense if the pack is cool to remove any good and apparently undamaged cells ASAP just in case it goes to poo again.The early remedy for R/C packs was to immerse them in a bucket of heavilly salted water then later pierce the foil bags of the packThis sort of optionhttps://oscarliang.com/dispose-lipo-battery-safely/Generally if the cells are temperature stable these days the plan is to fully discharge them and dispose appropriately in battery recycling options.Dumping the heat still remains key to getting it under control initially and avoiding combustion if possible.

author: Siwastaja
author_rank: Super Contributor
timestamp: May 13, 2019, 08:04:08 am
content: Quote from: beanflying on May 13, 2019, 07:35:28 amDo note that they don't manufacture lithium ion cells, and while a lot of advice in this document is generic and usable, some specifics could be misleading (for example, instructions regarding lithium metal cells).

author: beanflying
author_rank: Super Contributor
timestamp: May 13, 2019, 08:09:32 am
content: True about it being general, it was just a file I found that had a decent procedural method laid out and it is the sort of approach you need to take post impact or electrical event.Give it a few more years of exploding Teslas it will be much better known how to manage and prevent large packs going up in smoke and if they do what to do and then what to do to clean up after.

author: stj
author_rank: Super Contributor
timestamp: May 13, 2019, 08:18:36 am
content: i can imagine 18650's going bang pretty easily,once they get hot enough the insulating washer at the top could melt/get bypassed causing a dead short - then the pressure has to overcome some pretty thick metal.as for tesla etc,put the packs on runners with electrically fired gas-rams on them like on some seatbelts/roll-bars.if the pack gets too hot - eject the warp-core(pack) onto the road!!

author: james_s
author_rank: Super Contributor
timestamp: May 13, 2019, 03:56:03 pm
content: Tasked with that I would use an aluminum partition. Aluminum is practically transparent to X-rays, especially at higher energies.

author: Daixiwen
author_rank: Frequent Contributor
timestamp: May 14, 2019, 09:32:57 am
content: I used to work at a lithium ion cell factory. It's not that easy to make 18650 to ignite when you want it. They have a circuit breaker that will isolate the positive electrode when the internal pressure increases.It is easier to do with lithium polymer cells, that don't have that circuit breaker. Just overcharge them and they will ignite.If you need to do this with 18650, first choose the regular cells with cobalt. They will probably be the easier ones to try. You will first need to fully charge the cells (4.2V). Then I can suggest two ways:- increase the temperature, then the circuit breaker will not be able to stop anything. The internal temperature of the cell must be over 130°C, and then the thermal runaway reaction will start- use a power supply to increase the voltage of the cell, but with a very low current, for example 5V 50 mA. This should bring the internal chemistry at a high voltage that will start the thermal runaway reaction without giving the circuit breaker a chance to react in time. The problem with that solution is that it can take a while before this happens so you don't have a lot of control on when the fire will startUsing a nail is another possibility. 18650 are indeed designed to not ignite when doing the "nail test", but the exact parameters of the nail test (speed, pressure) were defined by the manufacturers, and carefully chosen to be sure they would pass the test. I don't remember the exact parameters, but if you do it yourself and fast enough, on a fully charged cell, it will probably go boom. Obviously don't try this at home, use adequate protective gear, make sure the cell is held properly in place, and don't stand in the axis of the cell, etc... etc...

author: ThinkingGrenade
author_rank: Newbie
timestamp: May 16, 2019, 07:07:42 pm
content: Thanks guys, very much, wasn't expecting to get this many replies.in most cases a fire crew will just dump several hundred liters of water onanyfire. the 1500L per minute from a hose rapidly removes heat out of a fire, be it electrical or otherwise. the only real exception to this is a metal fire, where this could cause significant explosion. the packs i was originally talking about are not drill battery sized or E-bike packs but 15-25KWh-ish 300-400v battery packs.... i have never seen one of those go up before, but id like to.and like a few people mentioned, the rise of electric vehicles will see a rise in both electrical fires, and crashes involving large battery packs. i think this kinda training for more people will be helpfulthe purpose of this test is to find which method and what medium is best in a portable fire extinguisher (<20kg (BS5306). there will be complete wastes of time, like CO2, but we'd like to see if others are any real use on large battery packs. (id pick halon personally, but the Montreal protocol ruined halon for a lot of countries)this battery test might just have to go the way of heating the few cells in the center until they go, as by the sound of things im not going to reliably get a reaction at the touch of a button, so to speak.100% ill post a video of it.....

author: james_s
author_rank: Super Contributor
timestamp: May 16, 2019, 07:27:55 pm
content: I don't think halon would do much at all against a fire that has its own oxidizer. As far as I know, halon works by displacing oxygen and is used in places like museums and datacenters where water could be as damaging as fire. Taking away the oxygen in a room won't stop a battery meltdown.

author: AG6QR
author_rank: Frequent Contributor
timestamp: May 16, 2019, 08:52:48 pm
content: Quote from: james_s on May 16, 2019, 07:27:55 pmHalon does not work by displacing oxygen. It works by interfering with the intermediate products in the chain reaction between the oxygen and fuel. It is effective at concentrations of around three percent in air, which is not a high enough concentration to displace a significant fraction of the available oxygen.But your main point may still be true. I don't know enough chemistry to say whether it would stop a battery thermal runaway, but my suspicion is that it would not.On the other hand, it would be effective at stopping other nearby combustible substances from burning in air.

author: james_s
author_rank: Super Contributor
timestamp: May 16, 2019, 09:55:09 pm
content: That's fascinating, I looked it up and read a few more details, interesting stuff. I'm surprised it's being phased out, I wouldn't have thought the amount being released would be a big problem, it's not like everyone is shooting off expensive halon extinguishers for fun.

author: grizewald
author_rank: Frequent Contributor
timestamp: May 18, 2019, 09:12:33 pm
content: To avoid the problem of internal protection circuits stopping your fun, look for lithium-ion cells described as "IMR". This type is for very high discharge current applications and does not have a protection circuit included.

author: johnkenyon
author_rank: Regular Contributor
timestamp: May 19, 2019, 07:28:29 am
content: As I see it, there are two parts to this - the electronic side - getting a cell to fail (and fail quickly with lots of heat generation), and then the physical side of getting a failed cell to trigger failure in other cells.A look at the accident reports for the Boeing Dreamliner battery failure will yield information how they mitigated the risk from individual cell failure - do the opposite.I reckon that placing cells in close thermal contact with each other, restricting ventilation (to retain heat and emitted gases) and possibly generating a spark to ignite any hydrogen given off will probably give the extreme/worst case failure mode for a battery pack that would be useful for firefighting training.

author: Rerouter
author_rank: Super Contributor
timestamp: May 19, 2019, 10:47:58 am
content: You don't have to get that crazy on the math to work out some numbers.Air has a specific heat of about 1kJ/kg e.g. how much energy it takes to heat it by 1C,Then you have a Convective Heat Transfer Coefficient of 10 to 100 W/m2K for most passive cooled devices.https://www.engineeringtoolbox.com/convective-heat-transfer-d_430.htmlSo your losing 5-50w of heat by convection by the time the exterior of the battery has reached 150C, tiny in the scheme of a short.http://www.inforlab-chimie.fr/doc/document_fichier_279.pdfNow a 18650 cell has a specific heat of about 80 kJ/kg, so to heat a battery up from 20C to the ignition point of 150, saying we have a 50g battery, takes at-least 520 kJ to reach that point. or just shy of about 4 minutes heated by a 2.2KW heating element.Now in the feild, the issue is generally the battery pack, essentially wrapping the product in a plastic wrap along side other cells reduces the available surface area, equally they tend to be fitted in other containers to protect the pack from impact like Fibreglass insulators, and being heated to significant temperatures over a longer time period, it leaves a lot less head room to peak to that temperature. when a fault happens,https://www.nasa.gov/sites/default/files/atoms/files/therm_runaway_test_18650_li-ion_clobato.pdfPrevious testing was also done with a heater, but they did far lower power over a longer time period.