I have a little bit of experience with gutting pre-made lightsabers and revamping things, but I'm at a point now that I want to go all in and build from scratch. I've been researching a lot up to this point, but I'm at a point now where I'm trying to understand my battery options, and what the real implications of the choices are. For reference, here are my choices so far:

Nano Biscotte v4
Tri-Cree Royal Blue/Green with White for FoC
2W Bass Speaker
Recharge port
AV switch (no LED)
Crystal Chamber with RGB LED accent light

So, that being said, through all the research I've done this morning on what batteries would run the saber, and just as importantly - FIT my design....I think I'm coming up with the 18500 as the appropriate choice. Many people suggest the 18650 for the Nano Biscotte, but my concern is the space restrictions.

So that has me wondering, what is the real difference between the 18500 and the 18650?

Obviously the length is a notable difference....and the reason I think going with the 18500 is the best choice for my plan. However, I don't really know what all the other technical stuff means. They are both 3.7V, so I'm guessing that is a wash. But the mAh are different. Is that strictly just the duration of the charge? If so, that basically means the batteries would provide the same experience, other than the length of the charge?

Here is a pic for reference on my project:

8tTGmL6.jpg

Thanks for any help