I have a cheap Magicshine clone light. With these lights, is the circuitry that cuts off the light when the battery pack is nearly discharged built into the light itself, or the battery pack? Or maybe both?

I was thinking about buying a water-resistant 4-slot 18650 battery holder designed for bike use, but one I was looking at doesn't appear to have built-in undervoltage protection. I can buy protected cells to put in the holder, which is fine, but could also try reusing some unprotected cells that I have. But I don't want to risk over-discharging any non-protected cells I may use.

The appeal for me is to be able to put the cells in a high quality charger that I know will charge them correctly individually each time. I know I can get 4-cell battery packs cheaper than the holder + batteries....

Thanks!