Car fire started by button cell battery?

[tchicago]

There was a report of a car fire that started from "button battery". Sounds really doubtful to me
https://www.usatoday.com/story/news/nation/2024/08/27/childrens-book-minivan-fire-north-carolina/74974685007/

Would be interesting if Dave can experiment with various kinds of coin / button cells to see if there is enough energy in them to start a fire.

[Phil1977]

As always it depends...

The rechargeable LIR2032 button cells can easily let a thin wire burn.

But how are the chances that a thin wire starts a car fire? Of course, if it´s embedded in thin paper or anything really easily inflammable then it works out. But if the resistance of the wire is too low or too high then nothing happens at all.

On the other hand, if you go to a also not uncommon 2450 size, things get more dangerous.

[temperance]

I don't know and never tried what would happen if you try charging a non rechargeable lithium coin cell. But I do know that UL has strict requirements on charging non rechargeable lithium cells.

[AVGresponding]

The article is confusing in that it talks about a "button battery" in the header and the third para, but then goes on to refer to it as a "lithium battery", then mentions advice from the US Fire Administration about "lithium-ion batteries".

I suspect it was actually a lithium pouch cell, Li-ion or Li-polymer.

I don't know and never tried what would happen if you try charging a non rechargeable lithium coin cell.

It will explode, but it will do it in the charger while being charged, not afterwards in the appliance.

[edavid]

The article is confusing in that it talks about a "button battery" in the header and the third para, but then goes on to refer to it as a "lithium battery", then mentions advice from the US Fire Administration about "lithium-ion batteries".

I suspect it was actually a lithium pouch cell, Li-ion or Li-polymer.

No, these books are powered by disposable batteries.

The one that was mentioned in the article uses 3 AG13/LR44 (alkaline) cells.  I've never heard of those catching fire or causing a fire (but I've never tried shorting one).  Of course, the fire department unhelpfully did not say if that's the actual book that was found.

[SiliconWizard]

Never heard of a small primary Lithium cell catching fire either. Sounds fishy if that's what is claimed.

[AVGresponding]

The one that was mentioned in the article uses 3 AG13/LR44 (alkaline) cells.  I've never heard of those catching fire or causing a fire (but I've never tried shorting one).  Of course, the fire department unhelpfully did not say if that's the actual book that was found.

They don't, the internal cell resistance is far too high for that kind of current. It's a relatively cheap and easy experiment to do yourself.

There aren't any primary cells, whether lithium, silver oxide, or alkaline, of this genaral size, that are capable of starting a fire by means of a short circuit. Any wire small enough to be fused by the currents these can produce would be too tiny and have too little thermal mass and therefore energy to ignite anything besides possibly black powder or something similar. Certainly not plastic tat cases.

While you can get these cells to explode by applying unreasonable V and I to them, these explosions are small, and again, of insufficient energy to ignite adjacent materials other than those that are designed to be ignited easily.

[themadhippy]

There aren't any primary cells, whether lithium, silver oxide, or alkaline, of this general size, that are capable of starting a fire by means of a short circuit

try a bit of wire wool,makes a for  great 1 use emergency cigarette lighter

[ejeffrey]

It's really hard to tell.  It would require very particular circumstances, such as a thin metal shaving left over from manufacturing accidentally shorting out, and happening to be in the place to catch the paper on fire.  It's theoretically possible but extremely rare.  On the other hand, there are probably hundreds of millions of these type of books and out there so an extremely rare failure mode might be observed. 

On the other hand, there is no further explanation of what the fire department found or what other possible ignition sources exist.  Given that we had fire departments sharing photos of car fires warning that hand sanitizer could spontaneous catch fire that turned out to be just made up stories, I don't put too much faith in their claims unless they make a formal investigation and release a report with all of the details.

[AVGresponding]

There aren't any primary cells, whether lithium, silver oxide, or alkaline, of this general size, that are capable of starting a fire by means of a short circuit

try a bit of wire wool,makes a for  great 1 use emergency cigarette lighter

A well known ignition material. You need the finer stuff for this to work with a button cell, and I don't ever recall seeing any products that had a wad of steel/magnesium/etc wool inserted that weren't specifically intended to be an ignitor.

[Siwastaja]

There aren't any primary cells, whether lithium, silver oxide, or alkaline, of this genaral size, that are capable of starting a fire by means of a short circuit.

By short circuit, probably not, but do we know there was a short circuit (near-zero resistance) involved? I'm quite sure that if my life depended on it, I could demonstrate setting something on fire with a small button cell. With zero-ohm load (short circuit), total power dissipation is indeed at highest, but it's fully on internal ESR, and thus dissipated by the full cell surface area (and slowed down by cell's thermal mass) - it won't be easy to get it hot enough.

But try with non-zero load, say load resistance matching ESR which produces maximum possible power to the external load. Now make the external load tiny, say a small piece of nichrome wire, and wrap it around something very flammable, and maybe you can have a fire.

[themadhippy]

and I don't ever recall seeing any products that had a wad of steel/magnesium/etc wool inserted that weren't specifically intended to be an ignitor.

brillo pads? or maybe  one of the parents was a plumber or painter.

[MK14]

[BrokenYugo]

I'm almost curious enough to get out 3x LR44 and some low value cheapo resistors, it's going to be very difficult to start a fire with ~600mW* in  a few seconds with no serious accelerant but I'd assume it's possible.

* https://www.duracell.com/wp-content/uploads/2023/07/LR44_Datasheet.pdf see 5 Ohms line on last page.

That said I think it's more likely something else started the fire and everyone blamed the book.

[BrianHG]

I don't know and never tried what would happen if you try charging a non rechargeable lithium coin cell. But I do know that UL has strict requirements on charging non rechargeable lithium cells.

Nothing.  After a charge for 24h at ~4v, you literally need to short them out for a few seconds before they will give you something like 2 additional months of capacity compared to the original 5+ years.

If the cell isn't designed to be charged, it probably wont be able to be charged.

1.5v button cells charge better.  They will last ~1 year after a 1.8v charge at 24h.

I don't know and never tried what would happen if you try charging a non rechargeable lithium coin cell.

It will explode, but it will do it in the charger while being charged, not afterwards in the appliance.

Wrong, I tried it.  Nothing happens.  The battery ERS is already too high once drained and it just goes even higher, way too high for any meaningful current required to make it explode.

[thm_w]

There are more photos here: https://ca.news.yahoo.com/childrens-book-blame-fire-inside-145911725.html

It seems unlikely that whatever started the fire would be identifiable at all. Look at how much of the seat burned.
There are also paper books under the carseat itself? Or were those on top and the fire started at the bottom, hard to tell.

[coppercone2]

cow says boom

Here is the facts of these cheap devices (button cell devices are the cheapest of the cheap, usually there is a form of respect for even AAA batteries, i.e. battery contacts)

1) the contacts are mega shit, often a point contact with a cell. Guess what happens if that bends, it gets jammed between the cell pos and negative. They just stick a sharp bit of spring wire out of a hole and jam it into the cell. Its whatever the designer "figured" might work because its just 'pressure'. With a better device they try to make some 'leaf' contacts that are marginally less shady. Usually the alloy is crap for a spring, and it can fracture off. Then you have a thin piece of metal rattling around in the battery cavity waiting to get stuck in the crevice between positive and negative on the crimp seal. Try a bend test on a legitimate vs alibaba battery holder and you will see what difference the choice of alloy and hardening does. I have seen 300% difference in durability.... and thats for a engineered battery holder. If they crack some shit out on a spring making machine good luck. Oh yeah and this mystery contact is going to go get mystery plated afterwards too (maybe)

2) the wiring is counterfeit. Expect copper clad aluminum or copper clad copper (electroplated) or copper clad steel. Usually wire resistance is 3-6x the resistance of a equivalent copper wire (electrical copper). If you strip it and flick it, it s basically like spring wire. Often might not have wire, just "bus bars" made of whatever (steel).

3) the switches are jury rigged from stampings with no ingress protection etc. Likely to get dirty and over heat and they can spark too.. many battery devices suffer from these bullshit switches. they get dirty and run hot and melt easily. Steel stampings that press into each other = switch. Forget about a spring load or contact rivets or anything half decent.

4) for LR44 and such, the battery cavity is often creative and ambiguous. I have some flashlights that use it, you can put 3, 4 or even 5 cells into it. It will work with all configurations (I expect when its over loaded that LED is cooking but the cells are pretty weak). They don't have a cavity sometimes, its just how much can you fit between some creative stamped metal with maybe a spring. They could engineer a stop into the battery holder, so you can't jam as many cells as you feel like, and are limited to the correct amount, though likely this will be a piece of shit plastic post that breaks off.

5) what reverse insertion protection? A good cavity will be strong, add reverse insertion protection and also have a solid stop to prevent you from adding as many cells as you think. When you start requiring more then 2 cells, the springs are so compliant you can end up fitting 3-4 in there. At 4 you deform it and might notice you did it wrong, maybe. I am pretty sure I can get 6 LR44's into this "advertisement" flashlight I found. I wonder if the die is going to glow like a ciggarette lighter.


Not to say there is not decent LR44 devices, I have seen some with solid cavities, nice contacts, good switches etc. But usually these things cost like $1

[MK14]

Could the button cell be incorrectly manufactured, and end up with raw potassium metal or something, which can then easily catch on fire, if it gets wet?

Maybe something acted as a magnifying glass, such as a water filled bottle, in bright sunlight, could have ignited the pile of paper books (at least one seems to have mentioned, in this thread).

What about the car wiring, between the boot, and front of car, could it have shorted out, under the rear seat?

If anyone smokes in the car, they could have put it (when still lit), inadvertently, by that child seat, when removing the child, when leaving the car.

[coppercone2]

the metal will rather quickly oxidize in the air and the cell will smell if the seal is bad. Its more likely they are too cheap to replace and fix the dies on the presses and it does a bad seal... you typically don't have lithium ribbon sticking of a cell, i never seen it get that bad.

[MK14]

the metal will rather quickly oxidize in the air and the cell will smell if the seal is bad. Its more likely they are too cheap to replace and fix the dies on the presses and it does a bad seal... you typically don't have lithium ribbon sticking of a cell, i never seen it get that bad.

Maybe a battery pack (USB high capacity), or something (electronic with lithium batteries), in the rumored stuff/junk, below the car seat.

Here is an example, of a somewhat small battery pack (USB), getting damaged and causing a fire.

[Someone]

There aren't any primary cells, whether lithium, silver oxide, or alkaline, of this genaral size, that are capable of starting a fire by means of a short circuit. Any wire small enough to be fused by the currents these can produce would be too tiny and have too little thermal mass and therefore energy to ignite anything besides possibly black powder or something similar.

Saft make primary lithiums with rated discharge current (pulsed) greater than 20A. That would easily start a fire, so you'll need to walk back the bold claim of all primary lithium to something significantly smaller like: consumer button cells.

Even energizer will happily point out the significant short circuit currents available in their consumer AA's:
https://data.energizer.com/pdfs/lithiuml91l92_appman.pdf
A few dozen joules? yep that's some significant hazard.

[coppercone2]

they have PTC in primary lithium cells for energizer


I had one that shorted out on me recently, it was 70C for a good hour when I left it outside. It was in a stupid mouse that uses 2 parallel batteries. Don't use them in parallel. However, it did not rupture, rather scary though.


Usually the problem is when the battery is drained too low. If you have 3 good battery and 1 dead battery, the device will keep drawing current through the dead battery until something goes for series.... because they have higher voltage, the cutoff will not engage in the device to stop drawing current at the normal point where batteries go bad (in smarter circuits).  In parallel I am not sure what happened exactly, but obviously it got a internal short.


That is why its so important not to mix and match cells to try to get things to work. When you put them in a device it should be cradle to grave, not retrofitting. I think its safe to use those partially depleted batteries in a simple device that only uses 1 cell though. Its all nonlienar so you can't get great results even if you try to match them by measuring voltage... sorry cheap skates... its more complicated then rolling up a tube of tooth paste.

[Someone]

they have PTC in primary lithium cells for energizer

Yes, as they happily explain in their public documents, such as the one I linked above. That doesn't stop it being possible to pull dozens of joules out of the battery in a short timeframe, which can be more than enough to start a fire.

[coppercone2]

that is their main use, high current camera flash charging and stuff. Thats what these cells were all used for up until the 2000's.

Its not appropriate to put energizer lithium into a cheap piece of crap device like my mouse. It used to go into hundreds of dollars cameras.

They kinda redid their marketing without changing the design too much, since AA flash cams died... keep the lines going. 


I think the main problem in general with all this stuff is that a mechanical engineer does the electronics because its simple component wise and the circuit ends up being literal crap. Plus its all avante garde "circuits", that is plastic on metal, press fit, using mechanical components unrated for electricity, for electricity, 'figured' stampings, etc. I saw art students doing a electronic lighting fixture and I thought wow, thats how its designed! (jam foil into a wedge to make a 'interconnect"). And when you add malfunctioning assembly lines and realistic design tolerances to the equation, it ends up being really fucking bad. ALso, atrocious soldering

Is putting a steel wire into a hole on a nickel strip and then jamming it full of plastic considered a good interconnect? 

[Someone]

they have PTC in primary lithium cells for energizer

Yes, as they happily explain in their public documents, such as the one I linked above. That doesn't stop it being possible to pull dozens of joules out of the battery in a short timeframe, which can be more than enough to start a fire.

that is their main use, high current camera flash charging and stuff. Thats what these cells were all used for up until the 2000's.

It's not appropriate to put energizer lithium into a cheap piece of crap device like my mouse. It used to go into hundreds of dollars cameras.

Why not in cheaper/smaller devices? I put those buggers in anything that needs a long shelf/off lifetime such as rarely used wireless keyboard, mouse, remotes.

You post that it has a PTC is moot, because a) no-one is suggesting it doesn't, but more importantly b) that PTC does not prevent fire in all circumstances (only some circumstances). Those energizer lithium batteries are capable of making a fire.