Does this happen in parallel or just in series?
As little as I understand this much seems clear (feel free to correct).
If cells are run in parallel it is as if isolated separate cells are running thus if one is lower when inserted and run it simply is the first to stop contributing as much, thus it just simply gets lower faster.
When run in series, it is like one giant voltage added cell and if one (subcell) is significantly lower then the other cells, once connected together they will exchange current to balance out the voltages.
If this plus actual load exceeds the “C” discharge rate then something has got to give, and the result can/will be thermal runaway.
Am I close?
The most obvious reason would be reverse charging of one of the cells. A.k.a one full and one depleted cell.
I don’t think all those thermal shock due to cold/snow etc are even close to doing this.
Can’t say more without knowing actual battery IN the light during the explosion - circuitry protected? Real LiFePO4? Knockoff? *fire?
well we know it was a “Fire” cell
Thats what i was thinking but will read the links Warhawk posted below
Guy was in Co…very cold there right now right?
wonder if the light was in the truck…in the cold
No protection circuit…cell reversal due to cold = massive current flow from the one good battery =
Just spit balling here though
Hope the scientist guys that got the batteries can figure out what caused the problem
I am surprised they are examining the remnants, around here they would say it was just bad luck and close the case
So much for all the people that used to rave about how safe lifepo4 supposedly was…
I would like to know whether the drop in was compatible with the voltage of two of those 3v cells.
This.
This isn’t the first time I’ve read about CR123 lights exploding.
The usual cause seems to be the cells not running down at the same rate. One cell runs down faster than the other. The cell with charge in it then reverse charges the empty cell. This causes the empty cell to immediately vent heat and oxygen which in a sealed flashlight body results in an explosion.
I’ve seen reports of this happening with various different lithium battery chemistries: CR123, lifepo4, lico, and IMR, even with quality cells and quality chargers. If you’re using lithium cells the safest option is to only use lights that hold a single cell.
However, it should be noted that even single cell devices can explode or catch fire. I haven’t read any reports of this happening with flashlights, but I have heard of it happening with cell phones, which presumably only have a single cell.
Cell phones use lithium polymer i believe, someone correct me if i am wrong
No one seems to want to address the very likely prospect that this may not have happened at all.
Seen this:
??
The guys who invented these batteries already did these tests. Including a fully-charged-18650-in-a-dead-short-rig test, which dumped all the current through the 18650 as fast as possible. All the new manufacturers do is replicate the process the inventors devised. Similar process => similar results, at least IRL…
Youtube may differ.
I’d wait for confirmation (even from Mythbusters) before inventing a “reason”.
If he is faking it they will figure it out pretty quickly. I think you linked the wrong video
My favourite li ion failure video is the cell phone review where they bash the phone with a small sledge hammer till the battery vents and the guy asks his buddy for some febreeze (as if that will make the fumes less toxic)
"I mean it's pretty rare. Some people win the lottery and some people have a flashlight blow up in their' mouth, ya know!"
that hat linked to a USA today website, the video might be posted on YouTube but it seems legit.
That’s one of my favorite li-ion venting videos too. Not too smart to puncture a lipo battery pack.
I don’t have doubts about the legitimacy of the story, but I was surprised that a lithium iron phosphate cell would violently vent and injure the user. These venting scenarios are usually associated with lithium cobalt rechargeable or lithium primaries in series. I guess LiFePO4 cells can’t be considered as safe as we had thought.
I’d like to see a more detailed investigation about this. I haven’t read the CPF thread, but maybe they’re speculating about what exactly happened?
Excuse me while I whip this gif out.
+1 Lights in series are much more dangerous than in parallel. CR123 have always been knows as dangerous. But… it doesn’t matter the make of the cell or the type of cell. I had just two brand new MNKE 26650, that I put in a 2x26650 light and within a couple minutes, one cell was hot as hell, (scary hot) and the other felt like it had never been drawn on. I always check after one or two minutes, when using a new light, or cells I haven’t used before. To me, parallel is safer than Series. Series is asking for trouble. I most always notice one cell much hotter than the other and tell me if I am wrong, I don’t believe protection circuits on cells shut down for heat?
Previously discussed in the ongoing thread, which has more facts and some good practice advice as well:
(page down if the web software just takes you to the top of the thread)
I used to put flashlights in my mouth often, I quit immediately when I started using Lithium batteries.
It was suprisingly hard to break that habit.
Luckily my only light with a bite grip uses NiMH or primary AAAs.