High self-discharge on Sofirn 21700 battery

Yeah, I see this all the time in NZ, so many customers of mine already have existing lithium flashlights yet are shaken by learning that they can explode if misused. I include a printout on battery safety with each flashlight and also have a page on battery safety I’ve copied and slightly tweaked from BLF.

I remember one guy complained about his Convoy C8 blinking at 2.8v, I learnt he ran all cells virtually to 0v each time in his vape and was annoyed he couldn’t do the same on his light.

One thing I never see mentioned is battery safety when mounting a flashlight on a rifle, button top must be used otherwise one risks the spring denting in the top and blocking the relief vent. I’ve had people questioning why I state “button top only when mounting” and after I explain a cell could potentially explode if that vent can’t open, I never hear from them again, probably went back to AA’s.

I’m never amazed by people who do dumb things and/or don’t bothered to read up on things that are potentially dangerous. It’s just the world we live in now where people assume everything will be safe and that they’ll be taken of because of…….reasons.

Lotta people have the cellphone mentality. Ie, run it down ’til it shuts off on its own, plug it in to recharge, rinse, repeat.

People who get “protected” cells assume the same. After all, it says “protected” right on the tin!

But doesn’t Sofirn add protection circuitry to these 21700 BAK/Lishen cells?

Is it this protection circuitry that might be to blame for high self-discharge?

I have a Sofirn 5000 mAh 21700 cell.
It is unprotected.

When HKJ tested it, he noted that he tripped a protection fuse in it. Based on that, I assumed it was protected, but maybe I misunderstood something?

Mine looks a little different than the one that HKJ tested, but the one that HKJ tested is 71.0mm long, and at that length I think protection would be impossible.
Protected cells are typically at least 4mm longer than unprotected cells, so I’m not sure what HKJ is talking about.

I’m guessing it’s just basic overload/overcurrent protection that’s built into the base cell, but it doesn’t have the proper “Protected” circuitry that also triggers during over/under voltage conditions. So maybe Sofirn did not add anything to it afterall?

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