https://spicy3dprints.com sells some really nice battery cases, including small sizes.

Glass “occlusion devices”?

I don’t really know much about neopixels, what do they need in terms of control, does it have to be a constant signal or can they just stay in a mode until another mode is set? How many MCU pins do they need?

Aux can’t be set to anything but high or low, so advanced colour mixing can’t be done, if that’s what you mean.

It is possible in theory to use some colours on low and some on high at the same time, but the brightness difference would make the low invisible.

Also, it can’t be done with PWM because the MCU wouldn’t be able to sleep when the light was off/locked, and there aren’t enough free PWM counters IIRC anyway.

Maybe if there was a smarter RGB LED, that could have 3 values set via serial and it has a chip on it to do the processing and adjust its outputs, but such a device would be too large to fit where the current aux LEDs go on any light.

Maybe a bad reflow giving poor heat conductivity to the MCPCB? Since the temperature is measured at the MCU, that could result in an LED overheating without the MCU going into thermal protection in time.

In general, recharging them before use is better - if you’re preserving battery life as much as possible the ideal profile is to charge them to ~4.1V, use until ~3.5, then store at 3.6-3.7 until charged for next use, ideally minimising time sitting at full. Going below 3.4ish takes progressively more out of the battery life.

Everything but lithium primary or eneloops in a light with a mechanical switch will have battery self-discharge (bonus: neither of these two battery chemistries leak). An e-switch adds a bit more parasitic drain, so the best bet for a light that won’t be used for a long time is CR123A or white eneloops, and if you’re not sure what the switch type is, you can just break the contact of the batteries.

Hmm, if a watch counts as a light, then technically my most expensive light purchase is my phone…

…oh no. Quickly, what light costs more than an S23 Ultra? 🤣