pi*R^2*H
14500= 7693mm^3
18650=16532mm^3
Or only a bit over twice the volume. The difference is greater if you remove an equal case thickness from both but I think for the chemistry and construction methods the 18mm diameter is optimum since greater diameters don’t lead to commensurately greater capacity but do have greater internal resistance. For the 14500 I thinks it’s more a case of the difficulty of scaling down layers that can’t just be shrunk in size/thickness.
I also think since the 18650 is the largest volume LiIon battery, it gets all the attention, so to speak, for improvements…
In the case of an 18350 vs 18650, the 18350 should be capable volumetrically of at least half the Mah of an 18650… Good luck finding one with 1700mah (1/2 a 3400mah 18650) or even over 1000mah of actual milliamp hours.
The high volume and ubiquitous nature of the 18650 size means it gets all the tech/chemistry upgrades first…
I am sure in a few years the capacity of 14500’s, 16340’s, 18350’s and the other sizes will catch up to where we are now in 18650 power, but by then the 18650’s will have a genuine 5000+Mah…
I would love a real 1700mah 18350 and a 1500mah 14500….
I just wasn’t sure that “cmwr” understood how LiIons are made. They’re not like a dry-cell with a homogeneous mix in a can where volume has a more direct bearing on things.
I think you’re both right regards the 18650- it does seem to be the optimum size and it does get the improvements first, being as ubiquitous as it is. If someone developed the smaller cells as well as has been done with the 18650, they’d have a lot of the market to themselves till it settled out.
My biggest disappointment and only decent AA-sized LiIon light experience is with my SK68 clone. The 14500 boosted the output well enough but I still wasn’t seeing the run times I had hoped for- neither lasted like I had hoped for. I just don’t like the balance of power and runtime of a 14500 compared to most other sizes; it’s neither fish nor fowl to me and I see a lot of concurrence here on BLF though we have it’s proponents too, just fewer in number. Where the AA format excells is in cell availability- you can get AA cells everywhere and they’re cheap which is why they’re my BOB/GHB battery of choice. Now I just need a couple lights which can make the best of those cells.
Phil