Thanks :slight_smile: I like 26650 because it’s the highest capacity you can get in a standard cell right now, almost 6000mAh.
If I used 21700 I wouldn’t be able to fit a collar and lens in a thinner tube.

You’re right, ideally I would use a buck driver, but those usually require .5v or more battery voltage over the led voltage, so I would need a very low Vf LED.

That’s a great idea, having it heat expanded and contracted.
I was trying to minimize the parts though for rigidity and also heat sinking, which is why I didn’t want a separate pill from the body.

Thanks :slight_smile: