When I think about it…it doesn’t sound right.
You shine light at some object. The object reflects that light in one or more direction (usually scatters around).
Let’s pick the direction back. The object shines in that direction with intensity of X cd. So what reaches your eyes is X/distance^2 lux.
No idea why but running this cell in a PL47 will permanently make it a single mode only. No burnt smell but something must have shorted…becareful!
Happened to 2 PL47 back to to back
Ah, yes. The dreaded Vapcell “Widowmaker”… 
Wonder why?
That’s super weird…
Never heard of something like that happening.
I am using gold vapcell 40t on my pl47. It working fine… I will be careful and monitor.
The depressed "inny" top on those Vapcell cells are nasty. I bought one, but not happy with it - I commented in HKJ's review thread here: https://budgetlightforum.com/t/-/54274. Mine does work fine in a C8F 21700 but still waiting on my PL47. Not sure but could be the an issue at the batt+ end if the PL47 is using a button and not a spring, or soft spring. Or the big flat tail batt- end may cause issues, depending on how that driver works with the aux LED's (I'm not sure if they are strictly MCU controlled or not).
I’ve got a couple of Vinh lights, started with a K40vn Fiat Lux, and bought about half a dozen after that.
Then unfortunately I had a bad warranty experience for 2 of my lights just after he brought in his Skylumen warranty cards, wasn’t interested in fixing the lights so I simply stopped buying his lights.
He is a nice guy and generally excellent at replying to emails.
Edit: bit of pub trivia for you all, Vinh once banned Wolfdog from buying any of his lights, then revoked the ban, now Wolfdog is his #1 lapdog 
Vinh:
My Flashlight fan self is started to be 5 years ago. I started with twisty pill Convoy C8 7135 stacking and XM-L2 dedoming. For the last 1-2 years I followed your work more-less and your builds inspired me a lot and in the last year if a new led came out I try to be the first who mod a flashlight with it It sometimes happen sometimes not. I also sell a few modded lights but not do it for a living. Still hard to manage time and hobby and I make a lot more than I publish also because time. So I really understand what you talking about. Nowadays so many high power stock light came out that I often suggest people to buy one stock instead of me mod one because stock have the same output or nearly the same but it is cheaper. Also I know that a one hand built light will be more precise than a mass produced one. And if I do a mod for cheap not the money I worry about but the time I take it from my family. And that not worth. So I do my mods mostly at my regular work but in free times when everything going on it’s way fine.
Keep it up and do insane mods!
I love pub trivia!
IIRC I think Vinh’s character was in a Seinfeld episode……….
“No flashlights for you!”
PS. Watt was Wolfdog doing to annoy Vinh? Hounding him?
Flashlight Nazi hahahahaha!!!
Yeah it was many years ago, he was being his normal annoying self I guess and caught Vinh in a bad mood.
Since then he has unfortunately come to BLF to get in on our GB’s and gloat about the performance of his V54 lights.
Hey in Vinh’s kind of business I didn’t think it was even possible to be in a dark mood.
Rumour has it he is lucky to get 4 hours sleep per night
Well, his work is one of the very few where you can only test your work during nighttime only!
I have 4 Vapcell NCR21700A. Two recessed top and two button tops. I tested all four in my PL47 219B and PL47 XP-L HI. They work fine just like any other batteries. My recessed top was never charged because I haven’t bought a charger that can charge them yet so I haven’t tested the recessed version under full charge.
Just find some small magnets and they’ll charge fine (Home Depot has some)
What goes wrong in your reasoning is that you use lux while your reasoning is correct if you were to use lumen.
If you are at 1 meter from a light source (say, that illuminated watertower), the amount of light captured by your eyes is A lumen, coming from a light source that has a surface area B . If you move away to X meter, the amount of light captured by your eyes will be A / X2, but the apparent size (surface area) of the light source is also reduced, by the same factor X2. So the intensity of the light source remains the same, but with X2 less light from a X2 smaller source.
Doubling the distance does not reduce the light entering a certain area (eg. your pupil or the sensor on a luxmeter) by a half, it reduces it by 1/4.
^ sure enough, that is what the 2 stands for in the X2 (X square) in my story. This is not what the reasoning is about, and the picture does not explain what the reasoning is, it does not show that the observer not only receives less light through his pupil but that also that it comes from a smaller source (which part the picture is not about), leaving the intensity (how bright it looks) the same.
As long as the light source has a finite size on your retina, such as a recognisable water tower (it does not appear as a point source) this is valid.
Same happened to me, but with LG that I bough with the light from Fireflies. At first it worked fine, but after I unscrewed battery tube and screwed it back, it powers by screwing tail cap only. Button does nothing.