Time to adapt the 21700 standard

18650 no longer makes sense. 21700 is the future. All Tesla models for example are made with 21700 so that will be the dominant cell in the future. They are being made by the billions.

I am not interested in any led improvements, what I have is plenty but energy source needs drastic improvement.

Does the 21700 give a "drastic improvement"? Because Tesla like it must I too like it? What is the 18650 or 26650 not doing that the 21700 does?

I would have to disagree.

18650 batteries still deliver the most Watt Hours per Volume and per Weight, and outperform 21700 batteries.
NCR18650GA: 266 Watt Hours / gram, 0.74 Watt Hours / mm cubed
Samsung 21700 48G: 256 Watt Hours / gram, 0.70 Watt hours / mm cubed

Specs above may vary a little if different batteries are selected, but I chose two of the top performing ones with decent current draw capabilities.
Even if the 21700 battery eventually outperforms the 18650 with regards to capacity vs weight and volume, the 18650 battery is still more compact and I favour this in my flashlights.

As to where the market trend is going, 21700 is certainly gaining popularity, but I personally still prefer 18650 for its smaller size and better performance.
26650 batteries are lagging behind in performance relative to their weight and volume, but if the same technology goes into those, I think they have the potential to still be relevant in the future.

Yes, beside the advantages of 18650 mentioned above, it's higher surface to volume ratio means it can stay cooler for longer under high load conditions (like we like to use our lights).

But, whatever other reasons, the real issue for me is that the 1x18650 size of light is the largest that is conveniently pocket-carried. 21700 just gets too bulky. It's okay for hand-held, or a coat pocket, but no good for EDC.

My EDC is a very slim 18650 light (BOSS70), and its ~1.0" width is at the very maximum for daily carry, IMO.
My car lights are slightly larger SF 6P-type formats; a single 16650 or 18650 is about the maximum I'd want for a handy car light.

On the other hand, my 'kitchen counter' light is a larger SF U2; and judging by all the love for the larger Malkoff lights, I could definitely see an application for the 21700 format here - household / garage / backyard lights, that sort of thing.

So I really see a good role for both formats - but no way am I EDC'ing a 21700 light, no thank you. :-/

Another plus for 18650 is the availability of batteries vs 21700. You can get 18650s out of a lot of stuff these days if you need a few like power banks and older laptop batteries and a lot of tool battery packs. 21700 makes for a larger size that IMO could be a big negatives especially if you stack a bunch of them together like these larger tool battery packs. I think cost/Wh is won by 18650.

In another thread, I dealt with a friend's 21700 light. Or so I thought. Realizing later it was a light designed to take a 3x AAA carrier, that happens to be 65..70 mm long, and around 21 mm diameter. So light also takes 18650's with sleeve or a bit of leftover space on the side, 20700's and 21700's (dunno about protected versions of the latter though). On the cheap end, such 18650-or-3x-AAA lights are very common. Have one myself that's built very similar.

The point: for any 3x AAA light that people find acceptable size wise, so will a 20700 or 21700 based light. And such lights are already on the market in large numbers.

It's not a big difference. Whether that difference is too big or not, is a matter of taste and most people won't care. I don't consider 18650 lights 'pocketable' anyway. But fine for car trunk / garage / backyard use etc. So I suspect uptake of 21700's (or 20700) will very much depend on availability / cost of the batteries as compared to 18650's. If price difference becomes small enough, surely the marketing folks will run with those extra mAh's... :tinfoil:

NPL said:

26650 batteries are lagging behind in performance relative to their weight and volume, but if the same technology goes into those, I think they have the potential to still be relevant in the future.

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Looking into it recently, I was a bit surprised how small the capacity difference between (good) 21700 and 26650's are. Probably a case of optimisation / research money poured into the 21700 format.

As I understand it, for electric vehicles 21700's are preferred over bigger cells (for now) because of cooling issues. The bigger a cell gets, its volume vs. surface ratio increases and thus it has more difficulty shedding heat losses. I can imagine that as cells are improved (lower charge/discharge losses), attention may turn to bigger sizes like 26650, 32650, or some other new format. Also remember 26650 is roughly the same diameter as a C cell which people have used for ages.

It IS nice that all these cells have roughly the same length. For example it shouldn't be hard to find a 26650 host, that also takes 21700, 20700, 18650, or even 3x AAA using a carrier (all with sleeve). Apart from using sleeves / carrier and bigger-than-strictly-necessary for those other formats, there's hardly any downside to that. :twothumbs

Btw: 18650's aren't going anywhere! Take for example a laptop pack: cells are always arranged 'flat', for example 2 rows of 3. Use 21700's instead of 18650's, and (all else staying the same) that battery pack becomes 3 mm thicker. 3 mm that designers either have to shave of the laptop's internals, or end up with a 3 mm thicker laptop. Likewise for power tools: go with bigger cells, and either you wind up with a bigger / heavier battery pack, or you have to use fewer cells, read: fewer in series, which translates into a lower total voltage, which has its own downsides. Not gonna happen. Both 18650 and 21700 have their own applications, and both are @ the focus of intense research so (up to a point) increased battery capacity will come automagically.

Overall, I think it will be a matter of production numbers, and cost. Supply and demand. IF other car manufacturers follow, Tesla's lead; then the demand for 21700 cells will far outstrip the flashlight demand for 18650's. The tool suppliers are not concerned with the weight of their batteries, they want run-times, and profits! IF battery manufacturers switch to 21700 batteries the cost will go down, and IMO, they will be the standard.

Who buys 16650's anymore? That was not a typo. Where do you get them?

Yeah, like 21700s are going to fit in new thin laptops..

The most often humanitarian error — to ignore the "boredom" of numbers. Now is the question: HOW 21700 cells are being used in Tesla battery? The answer: they are artificially cooled. This is why their worse heat dissipation ability is not an issue there. To get their full potential (high current ability) in a flashlight you need it be liquid cooled... Otherwise you get only extra weight and dimensions and, yeah, you look fashionable.

vadimax said:

The most often humanitarian error — to ignore the "boredom" of numbers. Now is the question: HOW 21700 cells are being used in Tesla battery? The answer: they are artificially cooled. This is why their worse heat dissipation ability is not an issue there. To get their full potential (high current ability) in a flashlight you need it be liquid cooled... Otherwise you get only extra weight and dimensions and, yeah, you look fashionable.

Click to expand...

Not necessarily as it depends on the construction of the cells compared to 18650s. It is possible that a larger cell could have less internal resistance which is a contributing factor to heat in high current usage.

n3eg said:

Yeah, like 21700s are going to fit in new thin laptops..

Click to expand...

The last laptop I bought (a couple of months ago) uses an internal LiPo battery pack. They don't even allow you to replace the batteries in them anymore! Laptops are becoming as disposable as smart phones.

Although I generally hate devices that don't have replaceable batteries, I do admit it makes the laptop much thinner and portable than would be possible with a 18650 battery pack. So, I guess it makes some sense?

NPL said:

18650 batteries still deliver the most Watt Hours per Volume and per Weight, and outperform 21700 batteries.
NCR18650GA: 266 Watt Hours / gram, 0.74 Watt Hours / mm cubed
Samsung 21700 48G: 256 Watt Hours / gram, 0.70 Watt hours / mm cubed

Specs above may vary a little if different batteries are selected, but I chose two of the top performing ones with decent current draw capabilities.
Even if the 21700 battery eventually outperforms the 18650 with regards to capacity vs weight and volume, the 18650 battery is still more compact and I favour this in my flashlights.

Click to expand...

Probably only a matter of time until the 21700 recipe is honed to meet 18650 in terms of Wh per unit mass/volume, especially with a volume customer like Tesla backing the formfactor.

NPL said:

26650 batteries are lagging behind in performance relative to their weight and volume

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I don't believe that 26650 cells are used in any great numbers by OEMs, thus there's little motive to improve their recipe.

Poppy said:

Overall, I think it will be a matter of production numbers, and cost. Supply and demand. IF other car manufacturers follow, Tesla's lead; then the demand for 21700 cells will far outstrip the flashlight demand for 18650's. The tool suppliers are not concerned with the weight of their batteries, they want run-times, and profits! IF battery manufacturers switch to 21700 batteries the cost will go down, and IMO, they will be the standard.

Click to expand...

To the best of my knowledge, Tesla is the only manufacturer that uses cylindrical cells for BEV packs. The other automakers use larger, custom-manufactured cells - presumably for cost reasons but perhaps they have other advantages. I recall that Tesla claims better thermals and overall reliability with discrete cells and at a cursory back-of-the-napkin level this makes sense - thousands of cells are going to have a far larger surface area:volume ratio than hundreds of cells and if one cell of thousands fails that's easier to mange than one cell of hundreds.

BEV manufacturers are primarily interested in energy density; power tool manufacturers are interested in power density. This is akin to how Panasonic 18650s top out at 3.5Ah / ~3C discharge while the likes of Molicell 18650s are 2.6Ah / ~13C discharge.

For high-power applications, 18650 is a bit advantageous relative to 21700 with smaller diameter, placing the innards closer to the surface and this improving thermal performance. However, I suspect the power tool manufacturers will find 21700s sufficient for their purposes and appreciate the bump in capacity they offer.

WalkIntoTheLight said:

The last laptop I bought (a couple of months ago) uses an internal LiPo battery pack. They don't even allow you to replace the batteries in them anymore! Laptops are becoming as disposable as smart phones.

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This is the reality of laptops - they're largely abandoning user-replaceable li-ion packs. To an extent, the shelf life of li-ion/li-poly has reached the point that it's not as important as it used to be.

idleprocess said:

To the best of my knowledge, Tesla is the only manufacturer that uses cylindrical cells for BEV packs. The other automakers use larger, custom-manufactured cells - presumably for cost reasons but perhaps they have other advantages. I recall that Tesla claims better thermals and overall reliability with discrete cells and at a cursory back-of-the-napkin level this makes sense - thousands of cells are going to have a far larger surface area:volume ratio than hundreds of cells and if one cell of thousands fails that's easier to mange than one cell of hundreds.

Click to expand...

And if you've seen the inside of a Tesla battery pack, they're doing a lot of cooling of those cells.

This is the reality of laptops - they're largely abandoning user-replaceable li-ion packs. To an extent, the shelf life of li-ion/li-poly has reached the point that it's not as important as it used to be.

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They also come with software that allows you to customize what the charge level should be. So, you can max out the charge at 80%, for example, to improve battery life. Bump it up to 100% for those rare occasions when you'll need it and don't have power nearby.

WalkIntoTheLight said:

They also come with software that allows you to customize what the charge level should be. So, you can max out the charge at 80%, for example, to improve battery life. Bump it up to 100% for those rare occasions when you'll need it and don't have power nearby.

Click to expand...

I run mine on shore power whenever available so as to minimize cycling. I ought toggle it to an 80% charge.

Poppy said:

Overall, I think it will be a matter of production numbers, and cost. Supply and demand. IF other car manufacturers follow, Tesla's lead; then the demand for 21700 cells will far outstrip the flashlight demand for 18650's. The tool suppliers are not concerned with the weight of their batteries, they want run-times, and profits! IF battery manufacturers switch to 21700 batteries the cost will go down, and IMO, they will be the standard.

Who buys 16650's anymore? That was not a typo. Where do you get them?

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I have several lights that I run on 16650. I purchased mine from Illumn.com.

--flatline

BTW, did the OP actually mean to say "adopt", rather than "adapt"?

Or, does he mean that he wants to adapt the 21700 standard into a more-usable format. That would make sense. I'm totally in support of adapting the 21700 standard to make it 18mm in diameter and 65mm in length.

I'm fine with 18650s and have lights that pull 15-18A, so good there.

I have 25 chargers here, so the added capacity really isn't an issue.

Chris

People still use AA and AAA lights despite 18650 existing. Size matters.

So far all of the big OEMs have been making both 18650 and 21700 cells using their latest and greatest processes. As long as that continues there will be no strong advantage to either.

On the hobbyist side of things 21700 appear to be selling horribly. I am updating the prices and inventories for my battery database and everyone is trying to get rid of their 21700 stocks. Fire sale pricing. 1 battery for less than the old 1000-units-bulk discount. (I should have most of those sales online within the day.)

Supply & demand. A decent 18650 can be had for € 2 /piece or even less. While a decent 21700 would set me back at least € 5. So the Ah's you get are much more expensive. Possibly because most of those 21700's will be going into electric cars (or make that: Cybertruck ? :laughing: ), powerwalls etc first. Demand outstrips supply, and that is unlikely to change anytime soon. Also:

Lynx_Arc said:

Another plus for 18650 is the availability of batteries vs 21700. You can get 18650s out of a lot of stuff these days if you need a few like power banks and older laptop batteries and a lot of tool battery packs.

Click to expand...

I'm sort of 'up to my neck' into 18650's right now (well okay... dozens ). Early on some were bought. But most of them I pulled from a discarded (but mostly good) e-bike pack, and several laptop batteries. And plenty more where they came from. Meaning (for me) they're effectively free if I'd care to stick some into a hobby project. 21700's on the other hand... $$

Don't get me wrong: I like the 21700 size. But 18650's are much cheaper / easier to obtain, and will continue to be so for at least a few years more. As for that 'fire sale': interesting... But in the bigger scheme of things, us flashaholics are not even a rounding error in the 21700 market.