21700 is the future

Scallywag · December 7, 2019, 1:23am

I’m definitely interested in 21700 lights for certain things. But I’m 95% certain I’ll never EDC one due to size. I won’t EDC 26650 either. The 30T sure looks fun for hot-rodding.

Muto · December 7, 2019, 1:45am

Own a Zebralight, great light but the tint is like as Howard Stern would say……………….
Butterface

Still puts out really great though…………

BlueSwordM · December 7, 2019, 3:26am

21700 cells are just a form factor.

Cylindrical cells can supports all kinds of builds and chemistries, so 21700s could be using a solid state electrolyte.

Valynor · December 7, 2019, 3:30am

What I am kind of waiting/hoping for is a Zebralight "SC70d", basically an as-small-as-can-be 21700 flashlight (scaled up SC64 model for 21700 cell use). With a 90+ CRI LED, of course :)

arow55 · December 7, 2019, 3:55am

General Motors just announced partnering with LG for new plant. Wonder what size they will use.

MtnDon · December 7, 2019, 3:57am

Pouches

SubLGT · December 7, 2019, 4:14am

An interesting 2018 technical article in the Journal of the Electrochemical Society, comparing 21700 to 18650:

http://jes.ecsdl.org/content/165/14/A3284.full

Some excerpts:

…Currently, a few different types of 20700 and 21700 cells are available commercially, however, to best of our knowledge there are no published scientific investigations on these cells. Furthermore, in different discussions, we found that there is a controversy on an increase of energy density by the cell format and a need to clarify this topic on a scientific basis. Therefore, in this work we wish to shed some light on the new format and its potential impact. To do this, we compared several commercial 18650, 20700, and 21700 cells (see Table I).

…The energy content per cell can be higher by ∼50% for 21700 compared to 18650. Therefore, for certain applications, less cells have to be built and used to deliver the same amount of energy.

…The higher energy content on cell level leads to potentially lower effort and costs in the production of 21700 compared to 18650 type cells and their packs. The benefit of lower cell hardware costs is likely to be caused mainly by less cell housings, fewer jellyroll insertions/closings/tab welding, and less cell formations per Wh. More produced Wh per existing station might also have a trickledown effect on the cost.

…The energy density does not increase significantly by changing the cell format from 18650 to 21700 type. Instead, for state-of-the-art cells, the energy density is mainly a function of the anode coating thickness, i.e. high energy cells with current material combinations usually have thicker electrodes. The study showed that it is very important to use comparable coating thicknesses or electrode loadings when comparing different active materials or at least give the coating thickness for later comparison.

…The cell resistance is negatively influenced by the electrode thickness and positively by the electrode area. For cylindrical cells these parameters correlate with each other. This contributes to the lower performance of high energy cells. Going from the 18650 to the 21700 format, the cell resistance decreases noticeably and shows a relatively flatter correlation to anode coating thickness. The reason is the larger usable coated cathode area in the larger 21700-type cells, especially due to the outer windings of the jelly roll.

…Increasing electrode thickness in commercial cells has a negative impact on the discharge rate capability. Cells with thicker electrodes experience higher losses by limited transport, resulting in lower discharge energy and underutilized electrode active material. The general trend for all tested cell types was found that the rate-capability is limited by the temperature on the cell surface due to current flow.

toddcshoe · December 7, 2019, 6:03am

I have two 21700 lights. A C8F and a FF E07. The C8F isn’t pocketable at all to me, heads too big. The E07 I can pull off occasionally depending on what britches I am wearing. Colder weather and it’s Levi’s 501’s. The E07 isn’t fitting in that pocket without it being quite unpleasant to carry. I am most often working or running around after dark. I appreciate the run time of a 18650. Even then it has to be a fairly small 18650. Zebralight or DQG mostly. Most tube lights are too long for my liking.

I carry 18350 lights a lot as well. Armytek, Jetbeam, Reylight or a shorty S2+. Don’t carry AA\14500 much. SC52w or Reylight if I do.

Weight isn’t really a issue for me. I am a decent sized fella. 6’1” and 230lbs. I always carry a full sized, steel framed pistol concealed inside the waist band in a quality holster. If I can make that disappear and not notice the weight of it much, I highly doubt I will complain about flashlight weight. What I don’t like is things hanging around in holsters, on belt loops, or otherwise outside of my pockets or waistband. Too many things to snag me up on my day to day activities.

Is 21700 the future? For some things I’m sure they are. For flashlights? Not so much. I mean it’s not really the future, they are already here. It’s just an option available if you need it. Some do, some don’t. When 18650’s came out I’m sure someone tried to make the same observation. Yet we still have 10180, 14500, 16340, 18350 etc…… Sorry if I missed your favorite in between or oddball size. Point is they all still exist and are still made today even though at one time, 18650 was the future. They are even making better quality, higher capacity and higher current versions of those cells than they have ever made in the past.

So even the old cells still have a future. We are just at the end of a very long line of users for these cells. If battery manufactures had to depend on the flashlight folks to make their livings, they would die of hunger before the end of the first quarter.

Barkuti · December 7, 2019, 6:42am

I don't give a suck.

riffraff · December 7, 2019, 7:26pm

Save me from the wee turtles!

mortuus · December 7, 2019, 9:19pm

if 18650 battery suddenly will stop production then i can see the 21700 taking over, otherwise maybe not idk ??

The_Last_Katun · December 7, 2019, 9:24pm

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

will34 · December 7, 2019, 9:33pm

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.

Barkuti · December 7, 2019, 10:11pm

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.

extremesquared · December 7, 2019, 10:25pm

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.

manithree · December 7, 2019, 11:37pm

Has any EV manufacturer besides Tesla ever used 18650? None of the major brands available in the US have, AFAIK.

SubLGT · December 7, 2019, 11:43pm

Not true. 21700 cells are currently being used in power tool battery packs, and outdoor power equipment battery packs.

extremesquared · December 8, 2019, 12:48am

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.

extremesquared · December 8, 2019, 12:44am

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.

SubLGT · December 8, 2019, 2:47am

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.