how strong a container needed to "hold in" a li-ion explosion?

Off-topic Chatter
1

Just curious: if a li-ion cell experiences a catastrophic failure inside a flashlight, the flashlight can explode. But if you made a room-sized ball of solid metal, with a li-ion cell at the core, the ball of metal would withstand the cell's failure. So, what would be the smallest size container that could withstand the cell's failure?

Then, if you made one or two tiny holes for the gases to escape, what would happen? Would the gases escape slowly, or would they still escape very quickly, and because of the tiny hole, would the gases reach supersonic speeds and would you hear a "bang"?

Or, if the container were 100% sealed, what would happen to the cell when it tries to explode? If the metal ball encompasses the cell quite tightly, so that there's almost no room for gases, what happens to the chemical reaction inside the cell?

2

I typically place my Pila charger inside a heavy metal ammo box with the cover down but not latched shut. This way if something does go wrong the expanding gases will have somewhere to go. Trying not to breath in those gases is another matter.

3

While we're on the subject of li-ion safety, what type of fire extinguisher would be able to put out an li-ion fire?

4

I charge my batteries covered with a large heavy strainer made from strong wire mesh. It's supposed to let gases escape freely, while keeping flames and flying burning particles in.

Never actually tested and I don't mind it wasn't. Wink

5

-----excerpt follows----

“Venting of isolated small cells (cellphone cells and smaller) seldom results in flame ignition. This is likely due to the limited volumes of vent gases released from these cells–that is, the gases become diluted before ignition can occur. In comparison, ignition of vent gases from 18650 and larger cells [used in some laptops] is fairly common: these cells contain more electrolyte (more fuel), and are usually used in multi-cell battery packs. If the flow of vent gases is ‘restricted’ due to the configuration of a vent port (typical in hard case cells), flames emanating from the cell will be highly directional (flames from 18650 cells are often described as ‘torch-like’).

“Propagation of cell thermal runaway has significant implications for fire suppression and fire protection. A fire suppressant or low-oxygen environment may extinguish flames from a battery pack, but the thermal runaway reaction will propagate if heat is not sufficiently removed from the adjacent cells. Responders to fires involving lithium-ion battery packs have often described a series of re-ignition events. Typically, responders report they used a fire extinguisher on a battery pack fire, thought they had extinguished the fire, and then observed the fire re-ignite as an additional cell vented.”

...

"... the FAA is not considering the many laptops with magnesium frames flying on long overwater or remote routes without any protection other than Halon and water. “If magnesium catches fire, it will keep burning,” he warned. Steenholdt recommends keeping laptops carried in cabins in containment bags as a precaution, especially on Etops trips. An in-flight fire stemming from lithium laptop batteries is inevitable, he believes, and when a tragedy happens, “the FAA will finally react.”

In considering the hazards of lithium batteries, one message comes through loud and clear: you’ll be much happier when you carry some kind of bag to isolate and contain a lithium-battery-powered device that spontaneously overheats or bursts into flame. While spontaneous combustion of lithium battery-powered devices doesn’t seem to happen that often, a fire-containment bag will help keep the fire from spreading into an all-out disaster."

----end excerpt-----

I own in a fire-safety bag.

Note that's "safety" not "safe" -- they can still vent gas that's burning; they'd add one level of safety.

Most of them seem to be sold by hobby shops and labeled for "lithium-polymer" fire safety.

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Also found:

"... Under different conditions of pressure, temperature and electric field, the active chemicals in a cell may break down or combine in many different ways. According to Guoxian Liang, of the materials company Phostech Lithium, the following combinations of the elements used in the cathodes of Lithium Iron Phosphate cells have been found in some impure products in addition to the desired active compound LiFePO4:

Fe3(PO4)2, Li3Fe2(PO4)3, Fe2PO5, Fe2P2O7, FePO4, Fe(PO3)3, Fe7(PO4)6, Fe2P4O12, Fe3(PO4)2, Fe3(P2O7)2, FePLi2O, LiPO3, Li2O, Li3PO4, Li4P2O7, Fe2O3, Fe3O4, FeO, Fe, FeP, LiFeO2, Li5FeO4, LiFeP2O7, Li2FeP2O7, Li9Fe3(P2O7)3(PO4)2, P2O5, and others. These compounds arise just from the cathode material, but there are many other elements present in the anodes, electrolytes, binders and other additives which are used in the cell, making many more combinations possible"

6

As far as I know, using a dry chemical extinguisher Type "C" and the even better Type "D" are what you'd want to use for a li-ion fire.

7

I use a steel cabinet w/ steel drawers for charging batteries - li-ions get charged in the top drawer so that a failure will not ignite the other batteries (or their associated equipment).

storage is in a separate, all steel tool chest.

you could certainly build something that could contain a li-ion that fails, but I don't think the explosive force is the primary concern - the flames are. If you didn't vent the enclosure, you would eventually have to release the pressure trapped inside.

You did suggest venting it - but something like this seems easier than building anything...

If you really wanted to go that extra step, you could use this in an enclosure that is vented out of the building w/ dryer tube/vent

http://www.giantcod.co.uk/lipo-charge-safety-23x30cm-p-406251.html

8

richie, what light is in your avatar?

9

Lithium metal will probably burn (once lit) in carbon dioxide - off the top of my head I can't remember.

Anything containing water is right out - if it is already burning it'll react extremely violently with water. Though a water mist would be a good idea to get the hydrogen fluoride that will be produced out of the air. It really is not a good idea to breathe in hydrogen fluoride.

AFFF is out.

Dry powder is probably the way to go. But they don't cool all that well. Or if your country's laws still permit it, carbon tetrachloride (tetrachloromethane) is good. Just remember it forms phosgene when extinguishing fires. Phosgene is not nice stuff.

My preference would probably be sand. Lots of it. Once it's smothered I'd dump tens of gallons of water on it.

There are substances that can burn wet sand. Well only one that I know of.

http://pipeline.corante.com/archives/2008/02/26/sand_wont_save_you_this_time.php

Somebody once spilled a ton of the stuff which must have been impressive.

From a great distance.

If I had to put out such a fire - remember we are only talking a few grammes here - I'd get the burning cell outdoors if possible. If not I'd dump as much wet sand as I could find on it. Then I'd go find some more wet sand and drop that on it. The burning metallic lithium is the least of the problems.

I cannot over-emphasise how nasty the gaseous products of a burning cell are.

As in: let your home burn down before you breathe any of them. Buildings can be replaced. Lungs are harder to replace.

10

Hey Dthrckt...that's my AE Xenide 25W HID. It won't be in my avatar to much longer. As soon as I get some photos of it, it's going on Ebay. I just never use it and seem to like these new compact LED lights that have been coming out.

11

Hey, my boss uses to tell this story! I'm doing my PhD-thesis in fluorine chemistry, and yes, chlorine trifluoride is VERY nasty. Even we don't handle it, and we use fluorine gas on a regular basis. That was big accident with the ton of chlorine trifluoride. They tried to distill it into a stainless steel tank cooled with dry ice, but the tank got brittle from the low temperature. Hence the spillage.

I also work with alkali metals, and my preference would be dry sand to extinguish the lithium fire. That way you don't get explosions from the hydrogen which can form when lithium comes in contact with water. Then, when the cell is done with venting, take a shovel, put the mess in a metal bucket, and put it outside. The lithium metal reacts slowly with moisture from the air, and after several days it is harmless.

BUT: I don't think you will see a lithium fire in a venting cell, but a mixture of burning electrolyte and lithium. And I reccon it will be over quite quickly, unless there are more cells in a pack that vent in succession (in which case I would leave quickly). So fire extinguishers are a good idea, not for the cell but for your burning furniture. Lipo sacks, steel cabinets and ammo boxes are all good measurements in my opinion to keep your house from burning down.

And as Don said, don't breathe the fumes, hydrofluoric acid is vile stuff. It bites!

Just one question: has anyone here had a venting cell, or anything bad happening with lithium batteries? I always check the temperature of my charging cells, and I never had one that got even luke warm.

12

Someone else asked about experiences with cells in an earlier topic. I had one -- over-discharged a several-years-old CR2 LiIon (showed 2.something volts when the light quit lighting up, oops); tried putting it in the charger, it showed full almost immediately; put it away in the metal box. Came back a few days later and it had discoloration around the vents and 0.0 volts. Smoke alarm hadn't gone off; no sign of damage except the brown stain right around the little vent holes at the positive bump.

13

WOW Don, that's crazy s***. Hopefully I'll never have any issues with any of my Li-Ion's..

14

On topic of the gases.. lets say one cell burns off in a closed room of about 5*5 meters.. how long after that could you enter the room? Will the gases "settle" down or do you have to open all windows and stuff? Would the gases get through closed doors? Just wondering, in case anything ever happens..

15

I made a slate box for mine but never use it. I imagine sand would be the best thing to put out a fire.

16

yeah, I'm glad Don mentioned that. I have 5 gallon buckets of different grit blast media in my shop - one is fine sand - never occurred to me, even when I had a fire

17

I'd just sniff the air. Even if you have no sense of smell you will be aware of nasties. This doesn't mean stick your head inside the door and take huge lungfuls of contaminated air - this means open the door a crack and waft some of the air in the direction of your nose - you are sniffing, not snorting the air. Believe me, you will know if there's hydrogen fluoride in the air.

It really depends on the ventilation and humidity. The actual amounts of nasty stuff won't be large and will be quite happy eating just about everything - HF is not something that enjoys being the pure substance and will go to great lengths to turn itself into other stuff. Once you are sure any conflagration is extinguished, I'd want to run a water mist through the air to be sure.

18

If I'd read this thread 6 months ago I doubt I'd ever have bought any flashlight related li-ion product. There seems such a difference of opinion on the real-life dangers associated with this chemistry. Plenty of BLF-ers regularly remark that they've been happily using cheap, unprotected batteries and $5 chargers for years, others won't even use li-ion.

From hank's article:
" In comparison, ignition of vent gases from 18650 and larger cells [used in some laptops] is fairly common.."
Really? To repeat Confusius' earlier question, has anyone ever had a first-hand nightmare experience? Or do you know someone who has?

19

20

I knew about the dangers of Li-Ion and still use them. Still I'm one of the more careful users. I use a 6$ charger (recommended here, shuts off at 4.19V) and Trustfire protected batterys in single cell lights only.

I charge my cells in a safety bag inside a metal cassette and when I notice the light gets pretty dim, I switch cells. Usually they are around 2.8-3V then, so thats out of the danger zone, even for unprotected cells.

I've read a few storys about people blowing up Li-Ion cells, but I think they were mainly unprotected or multi cell lights. Sure, there is some risk. But I think the chance of having a car accident still is higher than experiencing a Li-Ion malfunction.