Is there a technical reason why (for example) a Samsung 30Q only comes in 18650 and a 40T only comes in 21700? I would imagine when a manufacturer creates a new model they would make that model in all major sizes.
If they did that everybody else would be confused.
Look at the specs and it’s easy to understand what the 30 and the 40 reference.
Its more confusing now. Imagine if every size of the same shoe had a different part number.
You didn’t look at the specs and the complete part number.
Let me ask my question a different way:
Why isn’t there a INR21700-30Q
In other words, why don’t they have a 21700 version with the same drain characteristics but higher capacity (because its a bigger battery.)
If you look at say Duracell Lead Acid batteries for cars, they are the same except for the size and the CCA. When you want to get a replacement battery for your car, you don’t look for a particular part number, you look for your size. The internals are the same.
The 30 is in reference to the 3000 mah CAPACITY not the amp discharge rating. On car batteries the internals are NOT the same. Except for the fact that they are 12 volt batteries. Every single spec is different in each size other than the one or two models where the positive and negative posts may be reversed. And no that’s not for positive ground vehicles.
Yes, the spec is different because the CCA is different. When you buy a car battery, you specify the size only. The size will determine which CCA you get.
Lets forget about the question, I must not be explaining it right. Thanks for your feedback.
Battery manufacturers’ clients are large companies which like predictability, so when they make a contract for 100 million 30Q batteries they expect to receive the 30Q model with certain discharge curve, cycle life and cost, they can’t just replace it with another battery even if it’s better. Once Samsung releases a succesor of the 30Q with technology from the 21700 50S, let’s call it 30S (I hope), they still have to make 30Q batteries for the existing contracts, so they will only release the new model when there is enough demand.
When Duracell released the Quantum battery. They released it for all sizes. You can get a Quantum AAA, AA, C, D. Its the exact same spec and design.
So when Samsung makes a 50S as you say, why do they only release it in 21700?
18650, 21700, 26650 are all sizes right? Just like AAA, AA, C, D.
Imagine if the Quantum only came in AA, and the copper top only came in AAA. Would not make any sense.
This is what I am having a hard time understanding.
They will if you ask for 100 million pieces of each 
. 10440, 14500, 16340, 18350 and 26650 don’t have enough demand for them to bother so you can’t only get them from less known Chinese manufacturers, Samsung can get more profit from running a 18650 or 21700 production line than from a 26650 or 14500 line. If you scale a Samsung 50S you would get a ~7000mAh 26650, but the best we can get at the moment is a 6400mAh 26650 with some self-discharge issues from an unknown manufacturer.
Duracell targets the consumer market, which don’t have the same predictability requirements, Samsung lawyers just hate the lithium-ion consumer market. Also Duracell’s innovations often are just a new name from the marketing department.
Thank you, that was an excellent explanation. I think I get it now.
Also, Samsung has probably shifted R&D mostly from 18650 to 21700. While they might have the electrolyte formula for 30Q, 40T, 50S, etc., there are probably going to be structural differences as well. That would require R&D money to duplicate in a different cell size, and possibly re-tooling costs as well. So it is cheaper to continue to run a good-enough cell (30Q) on existing lines than to retool it for 50S (arguably directly superior cell in all ways) equivalent in 18650.
Also there are often premium options for automobile batteries (namely AGM options). These often have increased CCA ratings, increased energy storage ratings, or both. They’re generally available in only certain sizes, because the tooling to build them is different than for normal flooded auto batteries and they’re much more expensive (both to make, and to purchase as a consumer). When I worked in that world, we could get almost any flooded battery size, but had normal stock of only a handful and even through special order couldn’t get all of them.
Thank you, I appreciate the explanation.