Please add me to the list for one unit. Thank you.
Yes 50mm (or 1.968 inches 
Oops m=mm
Did you mean 50 mm??
I was thinking about reflowing 4x Nichia 219C 4000K CRI 90+ D240 LEDs instead of the XP-Ls.
Does anyone have an estimate of roughly how many lumens I can expect to get with this setup?
My crude estimate places the output at around 4000 lumens.
There’s many parameters playing a role, but my guess would be a bit lower, say 3200 lumen.
How well will the flashlight tolerate 4.35V cells as opposed to just 4.2V cells? IS there any risk or harm in using 4.35V?
Yes, there is a risk of blowing the leds. This flashlight is completely direct-drive and with high drain 4.2V li-ion cells it runs the leds close to their maximum. Running them even harder with 4.35V cells might be too much. You may be saved by the 4.35V cells not being high drain enough too maintain their voltage, in that case there is no reason to use the high voltage cells anyway.
Thanks, Miller! :+1:
All the 4.35v cells I have tried so far had significantly worse performance then a high drain 4.2V cell. They have pretty high resistance in my experience.
This cell (samsung 30B) seems to handle 7amp pretty well though:
http://lygte-info.dk/review/batteries2012/Samsung%20ICR18650-30B%203000mAh%20(Green)%20UK.html
It maintains a higher voltage, even towards the ends of its discharge.
If you compare the 5A and 7A discharge curves with the 30Q:
You’ll notice that the 4.35V 30B does not perform as well as the 4.2V 30Q.
That 30B curve looks pretty good to me, not for max insane 30 sec output, but for low and steady... Appears to be a nice cell for FET DD normal usage.
Not saying that the 30B looks like a bad cell, just that the 30Q would be superior for maximum output, which I assume was the point of using a 4.35V cell.
Atrocious drop at turn on, would be losing a lot of light for a long time before seeing any positive out of it.
The potential for 4 of them in parallel to pop emitters at turn on would make it totally not worth the effort. In a single cell use, with the high Vf of say the Nichia 333 UV emitter, then yeah, it makes sense. (I actually do use this cell for just this purpose, a high Vf emitter at 3.8A that places a high demand on the cell.)
I'm curious never heard of a 4.35V cell at risk of popping a LED. I've never seen high Vf coming out of a 4.35V cell - how would that work? The 4.35V cells have always been known for flatter discharges, but never heard or seen one measure output to a LED at 4.35V - does that happen?
I don’t see the advantage over say a GA cell:
Again, if you want a flatter discharge, the 30B is preferred. Sure, you won't get great peak amps out of it. Similar are those first 15-45 secs high Vf you get out of a SONY VTC5A - great cell to quote lumens and throw with for the first 30 secs. Look at high amp discharges of a VTC5A compared to a VTC6 or 30Q - you'll see the VTC5A advantage, but a short lived advantage.
Just as a VTC6 or 30Q catches up to a VTC5A (quickly), the 30B does it slowly and eventually - that's why I'm saying low and steady. It's an interesting cell actually, worth considering for some. I used to discount them immediately for their lower output as well, but I've known some on the forum who always liked the 4.35V cells.
If the 4.35V cells could be designed to be more IMR like, and those flat curves raise a bit, would be better of course.
A possible advantage, maybe more charging cycles for most chargers won’t fully charge it?
I was thinking about that too, if you only charge a cell rated at 4.35V to 4.2V, maybe you can get more cycles out of it.
Or maybe a 4.35V cell is a “native” 4.2V cell with different tolerances?
I’ve heard that some LiIon cells can even be safely charged to 4.4V.
Hello The Miller,
Please put me down for a 2nd unit. (1st unit is #1323)
I got into flash light addiction recently and within 2 months I’ve gotten more than 10 flashlights.