Batteries: 18500 vs 18650

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:

Attachment 16260

Thanks for any help :)

From what i read, its 15mm difference, not mA or voltage. The 18 means width in mm and the 500 or 650 means 50 or 65mm in length. If you use a wired battery, you can have the wires point towards the recharge port disc, and have them exit that disc and do the wiring there, should allow you for a 18650. Youll have to drill a hole in that disc of course. 19mm is 3/4", so you can judge from there, id use a spade bit or a Unibit.

mAh is the capacity of the battery. That and your load determine runtime. The capacity is higher on all of the 18650 options. There is only one 3.7 18500 option at 1400 mAh.

Thanks for the replies. Having no real point of reference so far, is there any estimation of how much time 1400 mAh would actually last powering a saber such as what I described above?

Blue and green at full draw is 2000mA. Then your white which will be variable because it won’t be active all the time. Then your small current draw for the crystal led and speaker. Let’s say 3000mAh for ease of math. That’s 1400/3000=0.467 hours or roughly 28 mins. Now as I said, your white won’t be active all the time so it most likely will run a little over a half hour.

Thank you very much for the help on understanding. I will have a resistor on the blue, because I'm going for a bit of a teal color...but not sure how much that would affect things. So it is basically the chosen battery's mAh value, divided by an estimated 3000mA. So, the 3 main batteries I viewed:

18500 (1400mAh): 28mins
18650 (2600mAh): 52mins
Panasonic 18650 (3400 mAh): 68mins

That's good to know. I also was refiguring my chassis design, and I might be able to move the recharge port into the pommel, which would free up enough space in the hilt for one of the 18650's....as well as just bit more room in the crystal chamber (which has been a concern).

Keep in mind, those aren't hard numbers, it is merely a guideline. There are other factors at play that will affect run times. The capacity values are nominal, not a guaranteed value. Perhaps more importantly, your saber will have an operating range, depending on whats in it, so it will probably only operate properly as low as about 3.3v. The discharge curve falls off sharply, so this will be close to the end of the operating time of the battery anyway, but it does shave off some available capacity from your real world usage. There are a number of other factors, but those are probably the ones that will have the greatest effect. That being said, a battery with twice the capacity will probably last at least twice as long, all other things being equal.

Quote:

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Originally Posted by jbkuma

Keep in mind, those aren't hard numbers, it is merely a guideline.

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^this.

Quote:

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Originally Posted by darth_chasm

^this.

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Absolutely. I think the numbers are a nice exercise in understanding the way it works, though. Will the 18500 get 28 mins? Maybe...but it will likely be in that general ballpark. And the 18650(s) will get around twice that much time....roughly speaking.

I was hoping to confirm the lower battery wasn't going to sacrifice brightness or volume....but I think that already seems confirmed.

Thanks again.