Interesting thread, even if it left the OPs original question behind 2,5 pages ago!
What seems to account for the varying specs from different manufacturers is whether they state “minimum capacity, ”typical capacity” or “maximum capacity”.
Furthermore it is probably also affected by which bins that get available for “hobby users” as single cells.
If all of the “A binned” cells go to battery pack manufacturers, and all we are getting are the lower bins, more variance in internal resistance and capacity is a given result of this.
This is something that will vary, not only between different manufacturers, but also between cell models, as they are adopted for different packs by different makers of such.
Yet another factor is how exact the manufacturing process is for different brands and models, ie: what portion of every batch ends up in which bin.
This may also vary from batch to batch.
(A good example from another, yet somewhat related, manufacturing is CPUs and GPUs. Where certain models and batches turn out so well that the ones sold with lower specs, which is typically where lower bins end up, are really all from the highest bin and just underclocked. Making some extremely reliable for and sought after by overclockers. Nowadays though, most are made like this, and the makers of CPUs and graphic cards have gone to great lengths to lock the lower spec products from overclocking and unlocking disabled cores and whatnot).
When it comes to “real world performance” the variation is a lot more due to what the individual user actually uses something for, and how.
I, for instance, use a D4 with quad 219Cs. On top of that, I mostly wear a suit and want my EDC to fit in a vest pocket, so about 10cm/4” is the longest anything that will fit properly.
Hence, I use a shorty tube and an 18350. (Just got myself five Keeppower 1835Ps for that and there really aren’t any competitors in either output or capacity in that size. Except other brands using the same cell).
I do however want the ability to screw on the long tube and get maximum performance and/or runtime with 18650s.
If I go “glamping” that includes a generator (and a PA system plus a bunch of DJs etc) in which case I can always charge my batteries. And if I’m bringing a vanful of gear anyway, I can also bring all of my cells…
If I go camping/hiking/biking/kayaking though, I’ll need to bring lots of spares and/or use the ones with the most runtime, given the way I use the light. This also applies to when I go to open air techno parties and don’t want to bring more than a small bag, yet might be away for the entire weekend.
Now, I haven’t owned the D4 long enough to really know what my “real world usage” really is. And summer “nights” here in Sweden consists mainly of dusk and dawn, never really dark.
When “glamping”, or in other words, arranging and crewing a 48h open air techno party on a small island, an efest 18350 lasted all Friday night, when I was actually working and used it at lower output to see what I was doing close up. On Saturday night though, I quickly “drained” a VTC6, and thought that the flashlight got a lot hotter a lot quicker. Although by then I was properly F’d up and mostly just having fun with my pocket sun!
My actual question:
The problem with such a compact and high power build as the D4 though, is that regardless of how well the battery handles high current, or perhaps even exacerbated by it, the emitters will get extremely hot in a very short time.
The worst case scenario though, would likely be with a cell that is just about able to continuously deliver the maximum current, as pulled through the FET by the low fV Nichias, while itself heating up quickly!
This is probably the case with the Keeppower (Yongdeli) 18350s, and in all probability with all of the high capacity “10A” 18650s as well.
I’ve read somewhere on this forum that the draw is somewhere around 16-17A on turbo.
For most applications, such as lighting a dark path or for close up work, I’m fine with the “highest” regulated level, ~150lm @350mA. And while the ramping interface is nice and allows for finding the perfect power level for any given need, I very much like to just “Let there be Light!” with a double click, and then get back to low with another.
So the question is: what will be the sweet spot in batteries for the ability to run it for a long total time on low while retaining the ability to also use turbo, preferably for somewhat long durations, given the restraints of the compact build and its inherent heat problem?
We do get really cold winters here in Sweden as well, but I’m not worried about that as I trust in the heat build up to take care of that. Based on lots of experience with a TrustFire light running both TrustFire and Sanyo 14500 cells. (Had to occasionally start on low, but never failed completely unless cell was already very low and temp below –15°C (toward 0°F).
I’ve already got a couple each of VTC6 and HG2 and plans to get a couple of 30Q and probably GAs as well while I’m at it, for further single emitter lights if not for the D4, where I do believe that they are still top dog.
Price really isn’t an issue, not because I print my own, but because I won’t be needing that many and won’t wear them out for years…
And lastly…
To really put the “High drain Vs High capacity” question to the test: (leaving 18650 size)
How about comparing the A123 26650, just 2500mAh, but LiFePO and rated at 70A continuous output, to a good 26650 cell with at least double the capacity, at a discharge level around what the other cell is rated for?
The voltage at which the high capacity overtakes the A123 might be a bad indicator as it’s a LiFePO… but still, sometimes looking to the extremes is the best way to determine the answer to a question where the difference is too small to be decisive!
And might be interesting for the D4S.