Will the 21-70 Battery (a.k.a. 21700) Replace 18650?

This is a tricky question.

Right now, the most common Li-ion rechargeable is the 18650. As soon as Tesla ramps up battery production for the Tesla Model 3, however, that will change. Tesla has announced that the Model 3 will use 21-70 (a.k.a 21700) batteries. They are 21mm in diameter and 70mm in length. The large number that Tesla will need means that the 21-70 format will immediately become the most common Li-ion battery.

Many members here speculate that 21-70 will become available, and perhaps common, in flashlight designs within a few years. Whether it will replace 18650 in the long run has yet to be seen.

For those who have seen CD, DVD, and even Blu-ray, fade in popularity, it is hard to predict that Li-ion formats will remain unchanged. The best we can do is try to look forward, say, five or more years, and make our best guess. 18650 is almost certain to be viable over that time range. Ten or twenty years downstream is anybody's guess.

If you want to look forward twenty years, your best bet, by far, is AA. That's a format that has been around for more than a century.

Is 21-70 the future? What do you think?

I think it may happen at some point in the future. The batteries tesla will produce for a long time probably won’t leave teslas hands. Its if they start making a deal with tool manufactures etc. I don’t really see laptops or powerbaks go with a bigger battery. It will increase size and weight. If anything I see them going with flatter more compact batteries. There are already size 10440,14500,16, 17650 18350, 18500, 26350 26650 etc multiple sized lithium batteries currently and they still havnt overtaken the 18650. Its still king. It would take a mass market switch to them. Which they may or may not be able to handle the supply them. Tool packs, laptops, etc would all have to switch over to this new size. If that happens then ya probably will become the new standard but many years away.

Even regular DVDs are still quite popular. It maybe a decade or more before it could happen. Manufactures probably sign multi year contracts with like makita, ryobi. Laptop manufactures etc. I don’t see the 18650 battery going anywhere in the near future. Even garden ligjts sre going to the 18650. If anything it seems like production is increasing not decreasing. Let’s not forget the millions of vaping units that run off 18650s. Even if this new battery takes over. The 18650 will still be around just like the other sizes mentioned above. They make up a very small percentage probably single digits of lithium battery sales but still readily available

I think the Panasonic 21700s will only available be in Tesla’s supply chain for some time. If other users of li-ion cells such as power tool battery packs start using them then we may see them enter the flashlight market.

Samsung is also using 21700 in their E bikes. http://www.greencarcongress.com/2015/08/20150826-samsung.html http://www.businesswire.com/news/home/20150826005361/en/Samsung-SDI-Unveils-E-Bike-Battery


Let us agree, that there are rumours about TWO different to-be-standard sizes. The 20700 and 21700.
Unsure to me if this is caused by erroneous calculations, or there will come a divine battle to settle this once and for all.

Yes and no. Articles were written about Samsung and about Panasonic.
So I have done some digging of my own and found: NCR20700B
If this is a fake than it has cost him/her a few hours of solid work.

All of the later stories I have seen, such as this one at Fortune, say 21-70. Initially, I was reading 20700.

I know your Internet research capabilities are top notch. What is the tenor of the articles your are now seeing?

The future of the 21700? I haven’t got a clue. But there was a recent industry conference on advanced batteries for the automotive industry.

A very interesting peek at what is going on:


Top notch or bonkers? The jury is still out on that one. I seems that Tesla from 2013 on has hinted on the abandonment of the 18650 standard. And in 2014 more and more rumours indicated the introduction of a 20700. But Elon Musk apparently has done some last minute math and has announced that 21-70 would become the standard (not only introducing a new standard size, but also a new standard description). This was last july at the Tesla Gigafactory tour.
Which makes more sense of the 21700 Samsung is developing for E-bikes.

Any idea what they are trying to push 21700 to? 4000mah minimum I would think. Maybe up to 4500 with the right technology. Panasonic expected to have the 18650 4000mah released by now

Thanks, Henk.

21-70 it is. With initial production due to begin by year's end, I doubt Tesla will back away from that size.

For carry in a pants pocket, 1x18650 is a tad larger than I typically prefer. Even the diameter of the ZebraLight SC62w is a tiny bit bigger than I like. In a coat pocket, of course, 1x18650 is fine.

In the hand, I think I would like 1x21-70 better than 1x18650. In a jacket pocket, the difference does not matter.

I say, bring on the 21-70. Even if it were to dominate the flashlight world, it should still be possible to get 18650 batteries for a long time to come. There should be no hurry, therefore, to sell the 18650 flashlights I currently own.

OK, looks like the info is out and the batteries soon to follow. Great article titled “‘Quantum Leap’ in Battery Innovations Presented at Eurobike”, full link: http://www.bike-eu.com/home/nieuws/2016/9/quantum-leap-in-battery-innovations-presented-at-eurobike-10127504

And the article also discussed the new 20700 Panasonic cell.

I was reading the other day some where the highest a 18650 can go is 4200 from Panasonic at around $40 a piece used with nano technology to make the sheets thinner. But can’t take the stress of today’s 2+ amp charging. And kept within industry use. With the slow charge and high cost no real market niche for it until technology improves It needs a low charge rate. These new Tesla celks will be 4200mah but can do rapid charging. It seems technology wasn’t advancing fast or cheap enough for Tesla to make cars go further without recharging

Panasonic is hold their cards close to the vest, but these guys published that in addition to a 68% output, a battery which is exhausted after 3 years will now last 12 years. Those are huge things. One has to assume that Tesla and Panasonic, with the resources they have working on this issue, have achieved something similar.

Nope- the 18650 is too well entrenched, too widely-used, too highly-developed, and too well-loved to be knocked off the throne by a newcomer. Perhaps in 10 years that will be different but I think my prediction is safe for at least 5 years.


I sure hope the 21700 (aka 21-70) becomes the next oversized battery to take the place of the 26650. It’s only 3mm larger in diameter and 5mm longer than the 18650, yet has a lot more potential for future development whereas the 18650 has already topped out, development wise.

Presently, many protected and hi-cap 18650’s are close to 70mm long and 19mm in diameter so we were headed in that direction anyway.

I’m hoping for a BLF-SE model using a slightly enlarged version of the Eagle Eye X6R as the general format, including the latest version of the BLF backlit tailcap as our next big group-buy!

Article: Huge leaps in e-bike battery capacity coming to e-bikes soon by Elliot Johnston Nov 4 2016.


“New, larger 21700 cell e-bike batteries from Samsung and German battery supplier BMZ, and a 20700 cell from Panasonic have pushed the envelope for e-bike power standards forward.”

“Energy density is higher for the new cells, meaning that 700Wh batteries are likely to be commonplace by 2018.”

“A 21700 cell can have a capacity of 4.8Ah, as opposed to 3.5Ah for an 18650 cell. ”

“The unit also comes with high quality materials including stronger conductors and a greater proportion of active cell material which allows for a claimed 50% increase in energy supply and a 68% increase in output.”

“…the development possibilities of the 18650 cell format are exhausted.”

Also, the newest LG HG6 (20-65) 3000mAh 3.7V 30A discharge current 20650 battery is being advertised for use in power tools.

If they want a bigger FF (and volume) vs the 18650, why not just use the already entrenched 26650? Stick a protection circuit on it and it’ll be a 26700.

Nahhhhhhhhhh…the 18650 is here to stay. Sure, any battery size may exceed it in production numbers, BUT, they will never exceed the number of 18650 sized battery tubes and hands that contain them.

No, the only thing even close the popularity of 18650 is the 26650.
Highly doubt people will want to go with a lower capacity battery than a 26650 anyway, and if they do then 18650 is perfect.

Tesla will make batteries in house and use them for their EVs and Powerwalls. Basically a closed system, no one else is making for Tesla.
So unlikely to have an effect
If they sell bare cells or get others to make for them then possible, though it would be many years if ever for phaseout of 18650, they are used in millions of devices that would all need retooling, and without a reason for mass defection it won’t be done.