So how come 26650 batteries don't have higher mAH ratings?

[idleprocess]

I have a 100 watt single cell vape box that uses the 26mm battery. It has a hohm-grown cell that touts 35 continuous and 50 amp+ pulses with over 4k mAh. Can't speak for the pulse part but it definitely lasts a lot longer than the 3000 some odd mAh factory battery it came with.

Nicotine vapes are still pushing the envelope for battery tech with those 2 and 3 (and sometimes more) coils cooking vape juice for the massive cloud lovers.

I can see a small market with flashlights, but the 18mm cell has the market sewed up for the forseeable future in my view.

Not overly familiar with vaping, but most of the boxes I see are 2x 18650, likely capable of bursts of >60A with two cells in parallel.

 

[Overmind]

It's because 26650 manufacturing is for now secondary to 18650 as priority, therefore is practically just a few years behind. In the cell industry the priority in the last few years seems to have been high current 18650s, which practically got from 1500mAh to 3000mAh pretty fast.

But this in time will change. It will be worth using in the new battery-powered cars 26650s so they will soon evolve better, as demand for them will increase. At this moment, the most usual ones are the ones in the 4800-5200 mAh range, just as the 18650s were mostly in 2200-2600 range until relatively recently.

 

[mattheww50]

As others have pointed out, there is no large industrial demand for the 26650 cell. The demand today is for the 18650, but that is moving to the 21700. That big demand pays for extensive R&D in the hope of creating a product that can gain market share and profits in the high volume market, so R&D money has tended to go into th 18650 and now 21700 products. Absent the large market, neither the total sales or the profits are going to be that great, so it does not pay to invest heavily in R&D for those products. Unfortunately it really is that simple. In terms of maximum output, like everything else, there are tradeoffs. Generally very high capacity comes at a price, usually lower maximum available amperage. The NCR18650GA at 3400mAh is just about the highest capacity 18650 out there (there a few that are higher, but they aren't much higher), and can put out 10 amps, if you need more than 10 amps, you will be hard pressed to even find a 3000 mAh cell, and I think most of the really high current cells are 2600 mAh or less. It would appear that most of the demand for the 26650 cells has been in high current applications rather than high capacity applications, hence the focus on available amperage instead of capacity.

 

[Overmind]

Exactly, focusing on amperage is what I see too. When testing good cells at 1A current the max I got out of a 26650 cell was 6000mAh. The average was 5500 and the cells were liitokalas and varicores maked between 5000 and 5200.

 

[fivemega]

18650 batteries have maximum capacities of 3400 mAH and higher. In theory, the maximum capacity of a given size battery should be proportional to its volume. So a 26650 battery, which has a volume that's (26/18)**2 = 2.08 times the volume of an 18650 battery, should in theory have a maximum capacity of at least 3400*2.08 = 7100 mAH. But in practice, the highest capacity 26650 battery I've seen is Orbronics 5750 mAH battery. What gives?

If the world was working this beautifull then we would have (3400/2=1700mAh) 1700mAh 18350 cell.

 

[orbital]

+

Length.

Two different size batteries having the same exact volume, the longer cell can usually squeeze more mAh.
Trust me, Tesla factored every size cell configuration,, 21700 won.

If someone came out with a 23750 @ 7000mAh true capacity, it would be interesting for proof of concept only.

 

[WalkIntoTheLight]

+

Length.

Two different size batteries having the same exact volume, the longer cell can usually squeeze more mAh.
Trust me, Tesla factored every size cell configuration,, 21700 won.

If someone came out with a 23750 @ 7000mAh true capacity, it would be interesting for proof of concept only.

I'm sure heat dissipation was a big factor in Tesla's choice, too. Surface area to volume ratio, matters. No point in designing a big 100,000 mAh cell, if the thing catches fire at 1 amp drain.

 

[orbital]

I'm sure heat dissipation was a big factor in Tesla's choice, too. Surface area to volume ratio, matters. No point in designing a big 100,000 mAh cell, if the thing catches fire at 1 amp drain.

+

Performance, durability, heat dissipation, size vs. capacity mAh

Regarding size;; imagine a container w/ really large marbles & picture all the open unused air space.
now imagine very small marbles, very little air space.
..I'm sure in finding the best balance/performance, the 21700 allowed just the right amount in air w/o wasting space for their large packs

meaning, bigger cells would just waste space.

(being 375V packs, wonder the amp draw at full output)