dougmc

I should also mention that most cell phones use a single LiPo or Li-ion cell -- therefore they're technically a cell rather than a battery (which is a collection of cells.)

You could argue that the protective circuitry makes it into a consumer product -- but if so, the 18650 cells sold for flashlights typically have a protective circuit as well.

Ultimately, I disagree with your point here -- at least some of the 18650 "batteries" certainly are are consumer "cells", intended for end-users to charge and use on their own. Now, they may only be commonly used in flashlights, and they may be relatively rare, rare enough that it doesn't make sense for places like Batteries Plus to stock them (especially considering that LiPo/LiIon cells degrade over time, even if not used) -- but that doesn't mean they're not sold as consumer cells.

Also, about the hobby shop having 18650 cells -- I've looked into this a bit, and it seems that A123 does sell some cells in a 18650 form factor. A123 cells are used for R/C use, but they have a different chemistry than the LiPo and LiIon cells we may be used to. In particular, LiPo batteries (including 18650s) are charged up to 4.2 volts, and you stop using it at around 3.3 volts or so. A123 cells are charged up to 3.6 volts, and you stop using them at 3.0 volts or so. In both cases, they call them "3.6 volt cells" -- but one gives the charge voltage, and the other the nominal voltage.

So if you put your A123 cell into your flashlight, it would work, but probably cut off faster than expected. And if you put your A123 cell into your LiPo charger, your charger would probably ruin it.

(I think the A123 cells may just be LiFePO4 -- which is often used in electric bicycles as well. Which is fine, but with somewhat different voltages you have to be careful about charging them, and the application that uses them as well.)