If you can not use protected, use imr cells, they are safer than cobalt chemistry. I do not think I heard those type explode or catch on fire.
Now i use purple Efest, in 3 cell l900, and 5 cell 200w hotwire, so far so good.
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Less than 2.5v operating voltage is below datasheet limits.
Lithium dendrites causing shorts is quite well documented.
The risks are real, just because it’s not happened yet doesn’t mean the risk is nonexistent.
There’s a thread on CPF of a modified ?maglite which had a cell in series go into thermal runaway or something. Results pretty scary.
Lots of users here stick to single cell lights to mitigate the risk of running cells in series.
Edit to add: I’m surprised (or maybe not) that your company is willing to accept the liability of such a risky set up, maybe they’re just not aware of the hazards.
I remember that one, it was an elephant with 8 cells, it even shattered glass terrace, . but we had extensive discussion and figured it was a user error, 4 of those cells, iirc were not charged and got hot soon after. we had another long thread rereading a battery exploding in a charger, well turns out that was not a rechargeable battery that blew up. but it is still extremely rare even when you consider myriads of no name cells out there. i do not remember many explosions with top brands, battery. We even had a thread about single cr123 light blow up while off, which in theory should not happen, but it did. we even had a cr123 light, iirc, blow up while on and in someone’s mouth, thou i do not remember if it was single or multi cell light. Still these events are extremely rare considering amount of light and li ion cells out there, i estimate around half or more are no name cells.
Ah yes, thanks for the correction on the light, I could remember it was modified and had cells in series.
User error was what I was trying to highlight in this thread. Using dubious ‘brand’ cells, discharging cells way below datasheet voltage, not matching pairs, no low discharge etc are all generally frowned upon here.
I deliberately didn’t mention the CR123a cases as the chemistry is different. I believe the one that exploded in a guy’s mouth was a 2*CR123a.
I found that thread, about the light that blew up in guys mouth, strangely enough his batteries were iron phosphate c123. something that should not blow up at all in theory,
No expert at all but have had an SP70 for a few years with two flat-top green Shockli 26650 cells and a magnet spacer and it has worked just fine and cells come out measuring the same voltage or within 0.01v. I never let them get too low and usually pull them off the charger a little early.
They usually do not catch fire, but they still can and will get hot and vent. All the energy is still released, just slower/less violently.
IMO the biggest safety hazard in flashlights is the fact that once a cell vents the light becomes pressurized sealed container, which will then blow up, potentially much more violently than any cell ever might. And in this context lifepo4/IFR failure is not much safer than than INR or ICR failure.
This is usually overlooked and people are often concerned about cells catching fire, but IMO what’s needed to make flashlights much safer is pressure relieve valve.
The only flashlight that I recall seeing that I’d call dangerous were some 3 cell LED lights they gave out at a local paarts supply, they were promotional items. They were LED lights that plugged directly into a cigar lighter in the truck.
I had a few of them and every one stopped working after only a few weeks. One went dead, the other blew smoke one day while charging. They were small lights, maybe 4" tops with a head about the size of a mini Maglite
After a tear down I saw that they used three short cells connected with tabs and soldered leads. Four leads went to the plug end, which had a small circuit board at that end, the other end had 8 wires going to a board that held the LED itself.
The front was threaded, the rear was crimped closed.
The rear ring would come loose, let the light rotate on the plug end shorting out the wires and batteries. Once shorted, they sizzled and smoked. I suppose if it happened in the truck overnight, it would likely start a fire. They were all metal and the internals were jammed in so tight that any movement caused a short.