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The Lounge 2019
- Thread starter Skylumen
- Start date
Help Support Candle Power Flashlight Forum
Today I am am all back 100%. Took WAY longer than i thought. I feel like a snake changing its skin. My facec skin is nicer now ahhaha
I'm surprised that I haven't seen 3 x 21700 pop can lights. I think a D18 or ROT66 would be pretty neat with 21700's. I'd even be interested 4 x 21700 X80GT or MT18. The body would be a little fatter but what a couple of power houses those would be.
...and since I'm on a roll of scattered thoughts, I could really use some assorted Skylumen logo stickers. I only saw the foot long, printed sticker on the website but I was really hoping for some logo stickers, in the 2-4" range, which I'd be happy to purchase. I thought I had seen these at one time but maybe it was only in my head.:laughing:
4*18650 offers better energy density.
Glenn7
Flashlight Enthusiast
We have man hands! I was thinking just go 4x 32700 @6000mAh each and be done with it :thumbsup:
Hahahhahha
Great news! I've got several uses for them, including a small fleet of skateboards!
But 3x21700 is larger in both length and diameter.
4*3600=14400, 3*5000=15000, 4.16% difference.
Quick calculation, please check me, I may have an error somewhere.
inner diameter of battery compartment for 4*18650 assuming .5mm free space around each battery is (18.5*sqrt(2))/sin(pi()/2)+18+1 mm. d18650 = 45.16 mm.
inner diameter of battery compartment for 3*21700 assuming .5mm free space around each battery is 21.5/sin(pi()/3)+21+1 mm. d21700 = 46.83 mm.
So volume difference [ pi()/4 * 65 * d18650^2 ] / [ pi()/4 * 70 * d21700^2 ] = 115.8%
Dividing that by capcity difference gives about 11% worse energy density. And slightly worse ergonomics added to that, many people find 4*18650 too bulky already.
4*3600=14400, 3*5000=15000, 4.16% difference.
Quick calculation, please check me, I may have an error somewhere.
inner diameter of battery compartment for 4*18650 assuming .5mm free space around each battery is (18.5*sqrt(2))/sin(pi()/2)+18+1 mm. d18650 = 45.16 mm.
inner diameter of battery compartment for 3*21700 assuming .5mm free space around each battery is 21.5/sin(pi()/3)+21+1 mm. d21700 = 46.83 mm.
So volume difference [ pi()/4 * 65 * d18650^2 ] / [ pi()/4 * 70 * d21700^2 ] = 115.8%
Dividing that by capcity difference gives about 11% worse energy density. And slightly worse ergonomics added to that, many people find 4*18650 too bulky already.
Glenn7
Flashlight Enthusiast
Couple of lights you maybe interested in Vinh, XXXX and another run XXXXX
Hope you don't mind me posting these here, if not I'll stop and maybe email you if you prefer or not at all :thinking:
CPF doesnt allow BLF links.
Hope you don't mind me posting these here, if not I'll stop and maybe email you if you prefer or not at all :thinking:
CPF doesnt allow BLF links.
Last edited by a moderator:
Has anyone experienced an Audril UI light that turns on when ever the battery is connected? I have a D18vn that turns on whenever the battery tube is screwed on and can't be turned off unless the battery tube is unscrewed. I suspect this isn't a UI issue but thought I'd throw it out there to people with more Audril experience. I'll probably have to send the light to Vinh, if it's a switch issue.
Glenn7
Flashlight Enthusiast
Sorry, point taken Vinh.
You've made some good points about the energy density but I think the figures are actually a bit closer than that, with an important difference at the end.
Using a cylindrical volume calculator and simply applying the 21x70mm format, it gave me about 97,980cm per 21700 x 3 = 290,940cm total volume. Doing the same for the 18650 gave me 66,162cm x 4 = 264,648 total volume. This makes the 4x18650's only 91% of the volume of the 3x21700's but the 4x18650's are only 93.3% the capacity of the 3x21700's. Quite close. Regarding weight, the 4x18650's are only 88.24% the weight of the 3x21700's, so a clear advantage there, to the 18650's.
Getting back to the important difference that I mentioned, 4x18650 placed side by side (2x2), have a minimum outside dimension of just over 45mm while 3x21700's can be placed together with a minimum outside dimension of 42mm. A light like the X80GT could have a 46mm battery tube instead of a 49mm tube and have 5.7% more capacity, albeit 5mm longer.
When I initially mentioned this, I think you'll see by my post that I was more fascinated with the idea of 3x18650 lights like the D18 and ROT having a 3x21700's option and 4x18650 lights like the X80 and MT18 having a 4x21700 option, fully understanding that they'd be larger but also have more runtime and less voltage sag. The X80 for example, even has that little handle that make carrying a fatter light an easier proposition.
In any case, I enjoyed considering the 3 vs. 4 cell discussion and the great thoughts. Fun to ponder!
Ah yes, not very clear, my apologies. I accidentally used radius instead of diameter but the volume results should be the same by percentage.
Cylindrical volume calculator by length and diameter...
21mm x 70mm = 24,245mm³ x 3 = 72,735mm³
18mm x 65mm = 16,540mm³ x 4 = 66,160mm³
66.16 ÷ 72.73 = .909 or 66.16 is 90.96% of 72.73
4x18650s are 90.96% the volume of 3x21700s or 91% rounded up, as I figured in my first results.
Once again and with appreciation, correct me if I'm missing anything.
Cylindrical volume calculator by length and diameter...
21mm x 70mm = 24,245mm³ x 3 = 72,735mm³
18mm x 65mm = 16,540mm³ x 4 = 66,160mm³
66.16 ÷ 72.73 = .909 or 66.16 is 90.96% of 72.73
4x18650s are 90.96% the volume of 3x21700s or 91% rounded up, as I figured in my first results.
Once again and with appreciation, correct me if I'm missing anything.
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With regards to the "diameter" of all the cells together, I measured them with digital calipers.
2 18650s (side by side) measured 37.08mm. The measurement is the same for 3x18650s in a triangle because the maximum width is still only as wide as two of the cells.
4 18650s (four cells in a square) measured 44.75mm across the X because now there's a large gap between the cells.
3 cells fit together with very little space between them, while 4 symmetrically spaced cells, as they would be in a flashlight have a substantial gap between them.
3x21700s fit closer together than 4x18650s even though 2x21700s together are wider than 2x18650s.
EDIT: pics added
44.75mm across the X (widest point)
37.08mm across the widest point or (same as two cells)
2 18650s (side by side) measured 37.08mm. The measurement is the same for 3x18650s in a triangle because the maximum width is still only as wide as two of the cells.
4 18650s (four cells in a square) measured 44.75mm across the X because now there's a large gap between the cells.
3 cells fit together with very little space between them, while 4 symmetrically spaced cells, as they would be in a flashlight have a substantial gap between them.
3x21700s fit closer together than 4x18650s even though 2x21700s together are wider than 2x18650s.
EDIT: pics added
44.75mm across the X (widest point)
37.08mm across the widest point or (same as two cells)
Last edited:
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