Yes this adds to my point. Those videos are/were guys vaping on what are called “mechanical mods”. Just like the name sounds they are a strictly mechanical device. You hold the button and the battery just dumps all its energy into the coil, making the coil heat up etc. Now, most of the mods have all the same electronic protections. The guys that still use mech mods (hopefully) understand ohms law and the risks of wrapping a sub-ohm coil.
Never ocurred to me until now to do some reading of info aimed at vapers.
Read some good stuff today that has helped me relax quite a bit about the potential dangers of using LiIons with flashlights.
Thanks everyone.
Doubt it. Lotta them feel that if they can’t fumigate the entire room with one drag, that it’s not enough.
On internal resistance and knowing when to retire a cell…basically with use (sooner or later depending on how it is used) the resistance increases so you get less juice flowing and more heat buildup. It’s a gradual thing and the performance (and charged capacity) of the cell diminishes over time. You can basically think of it just like a copper wire/cable. Maybe battery cables in a car are a good analogy.
When the battery cables get some corrosion through longevity and/or exposure to the elements, they develop higher resistance to the electricity trying to flow through them. If that corrosion gets high enough then you will notice sluggish starting, or maybe a click followed by the engine starting. If it gets worse, then that juice just can’t flow enough from the battery to the starter motor because the corroded cable is restricting the flow too much. Inside a battery it’s essentially the same.
Manufacturers typically rate the cells as so many charge/discharge cycles until the original capacity is diminished to 80% or something. At that point the cell still works fine, it just has shorter run time and perhaps more heat buildup in use and while charging it up, but it’s a workable battery with a lot of life in it still. For higher draw lights you may want to get a new cell then and use the worn cell for lower power lights or some other gadget.
The exception to the gradual buildup of internal resistance is when a cell is allowed to be reeaallly discharged……we’ve talked about that before but 2.5v is usually the recommended low point but it’s not concrete. If a cell discharges to that level then it’s usually still fine, just charge it up slowly and keep an eye on it…maybe measure it after charging to see if it maintains voltage over a few days, etc. If that cell is allowed to remain in that very low discharged state then the chemistry can do its chemistry thing and resistance will increase (where it probably won’t if you charge it up again asap). The lower that discharge point, the higher the chance (or guarantee) of increased resistance. At 2.0v or lower, most people choose to trash/recycle the cell and play it safe, which is smart. If a cell that low charges up it may still be alright but will show that reduction in capacity/increase in heat. That can happen in a brand new cell, not just well used ones. Generally our drivers aren’t going to let a light ever drain that low, but you’ve probably read about aux lights allowing it to happen if people totally ignore their lights that have an issue there…and a truly “dumb” driver that doesn’t have low voltage protection (an actual cut off for the circuit) will let it deplete entirely, or almost.
Best practice is usually to recharge at 3.2V or so, or even a bit higher than that, if your interest is in longest health/life for the cells. In regular use, taking them lower and charging them up is fine…most lights seem to put their cut off point at 2.8v or 2.7v to try and maximize run time and not leave you in the dark (say, cell is dead but you still need some light and maybe moonlight or low is enough to serve your needs for a bit). If you could keep your cells in a stasis near their 3.7v nominal rating, they’d be happiest. But we charge higher and we drain lower, so the more those two parameters are pushed and the more heat the cell sees in action…scrubs a little life away bit by bit. Generally don’t worry about it. When you notice on the charger readout or in performance/run time that the cell isn’t what it used to be, consider a new one, etc.
Hey! I really appreciate you Correllux. Many thanks.
I think I can finally relax and fully enjoy my flashlights.
For too long now my misunderstandings have had me believing that certain cells in combination with certain drivers could result in… Consequences.
Glad to hear it, CRC. You’re learned a lot over the last year or whatever, and you weren’t sure you could! Way to prove yourself wrong, in the best of ways. lol I’m sure you’ll keep learning more and more…your mods and accessories show that you’re hooked. 
Are you talking about your safety or the battery’s safety?
If first then just follow manufacturer’s datasheet and there won’t be any unpleasant surprises. Even malfunctioning flashlight’s termal regulation can hardly cause battery to catch fire. I’ve seen tests of high cdr batteries (maybe molicells) under high load during which batteries got heated to more than 100C.
Just stay away from ICRs and stick to original batteries of decent brands.