To recharge the 21700 I use my old chargers, Trustfire TR-005 and TR-006, they take 73mm long batteries. I’m waiting for other more modern chargers but for now I use these
I don’t feel much difference between my SC700D vs D4 size wise, but with the zebralight it just seems like the battery lasts much longer.
This discussion has no point. 21700 cells are a new format which someone came up with just because it was of benefit to his industry, period. 21700 cells are already here, they're not “the future”. Indiscriminately favouring some stuff over another is stupid. There are many applications for which 18650 cells are still better suited than 21700s, so long live 'em and any other different format.
Let me say, for example, that some of you probably think or even believe the 26650 format trails behind in technology. I sort of agree and it has its reasons, but let me say they're not going to dissapear anytime soon, not by a long shot. Power Long Battery is probably the main standard bearer of the category, I see they're very focused in LiFePO4 (best LiFePO4 26650 cells in the market right now). And regarding their li-ion NMC cells, they're widely used in buses, logistics trucks and etc. within the Chinese market. And when you think how BIG is their bus fleet, you can understand.
Both 55A and 50A cells are listed here but not there. I think someone said they were discontinuing the 55A, hope not. Or at least hope they develop 60x, 65x or better models. 
18650 is going nowhere within the next decade because of power tools. 21700 is not viable in cordless tools.
Also wouldn’t surprise me if some EVs continue to use 18650 even if tesla does not.
Has any EV manufacturer besides Tesla ever used 18650? None of the major brands available in the US have, AFAIK.
Not true. 21700 cells are currently being used in power tool battery packs, and outdoor power equipment battery packs.
Makes sense for large outdoor tools on platforms that don’t worry too much about universal batteries (milwaukee, ego). I should have been more specific: they will never be accepted in handheld woodworking tools like drills, drivers, and routers. And some cordless platforms try to unify battery packs across the whole line which keeps 18650s in the big tools as well (makita) and seem committed to that strategy.
Don’t get me wrong, 21700 are awesome — great for backpacking/biking lights, and I’ve switched to them for powering small solar projects. But the sky is absolutely not falling if you are depending on cheap and modern tech 18650s.
It’s not a strict EV, but Toyota did in the Prius at least, which is probably responsible for more cells on the road than the rest of the hybrid/EV market combined.
Power tool makers like Makita, Bosch, Ryobi, Metabo, Milwaukee etc are offering 21700 battery packs for their drills and drivers.
As one example, Makita has a new 21700 battery called the XGT 40V Max that they are offering for use with 6 hand held power tools: hammer drill, impact driver, reciprocating saw, circular saw, angle grinder, and rotary hammer.
Huh, that is interesting. Never seen those before. But those are likely to remain on the specialty tool fringe. Packs of 21700 in 5s2p (or in this case 10s) are too bulky for the majority of power tool users. Look at the amount of engineering and marketing that has gone into makita’s “subcompact” lineup.
If anything is going to unseat 18v 18650 in power tools it’ll be smaller cells or a radical change — like 4s1p 21700 if it can perform as well as the 5s2p 18650. Or some sort of asinine proprietary prismatic garbage. People who use these regularly are just not going to go bigger than the already very bulky current gen. I’m 6’6” and a little bit boggled by the clunkiness of 18v tools sometimes. I can’t predict the future, but I’d definitely be very surprised if 18650 based power tools disappear before 2040.
Ladies and Gentlemen can’t we just celebrate and embrace diversity. All batteries matter. Cute little 18350’s for EDC. 18650’s and the big brother 21700 for work around the place. Even that red headed 20700 and lumbering 26650 fit niches well. I prefer single cell lights and the cell variety allows lots of options. So no more haters.
:+1: It is surprising you got away with this comment, but it is so true!
Samsung is currently supplying 21700 cells to Jaguar, and is hoping to also supply two Chinese automakers, according to this 2019 report:
8 million a month, flashlights really are small fish for them. Thank you for the info.
day to day. (not recently) but I used to be in a suit most days. Usually that included a AAA keychain light of some kind and if I was doing retail with basement, or construction site tours, I would grab a 18350. Not even an 18650.
I have a PL47 on the way and it looks small so maybe I’ll try that and update.
For what most people use day to day, that’s more then enough. But I’ve lived through a blackout (our building only, flooding made FD cut the power to avoid getting electrocuted) where the windowless hallways were black once the emergency lights fizzled.
Just going to the community can and back, sure an AAA light would suffice, but if I were stuck somewhere that I might need decent light for a few hours, I’d definitely make sure to have a bigger donk at the ready.
And if we ever had another blackout like the one that killed the whole eastern seaboard, damnedstraight I’d want enough firepower to last me a while.
A twisted part of me almost wants another blackout, just to be able to use all my toys. 
Pff… not for the headlamps.
Unless it’s for those with a separate battery pack.
I allready got a batteries and flashlights for AA, 18(3)650 and 26650. These standaards provide everything I need. From EDC to power hungry builds.
I don’t plan on investing into this new standard.
Also, depending on the light, eg, the C8F, the fatter tube just seems better balanced (both look and feel) and gives a better grip, and in a pinch you can throw in an 18650 and it’ll work. Won’t even need an “adapter tube” for it, as if you’re really anal-retentive about the chance of the cell rattling around inside, a quick wrap with a napkin or tissue will take up the slack and even provide cushioning.
It’s already a decent-sized light, so the difference won’t be as much as an 18650 tubelight vs its 21700 equivalent.