Not knowledgeable enough to know, but would it be feasible to have the USB charging port built into the tail cap?
Assuming if it was, then it would have already been done and some of the manufactures would have perhaps brought out a range of tail caps to “upgrade” existing lights.
Aside from Olight with their magnetic taillight charger, I don’t see any others.
Requires proprietary batteries or you have to break the connection at the tailcap like Armytek.
I was wondering about that myself. That budget 26650 flashlight that popped up a year ago here, I can’t remember the name, had this. It was a tail clicky switch model. Also the Wuben L50 has this. It appears doable. Both take regular batteries.
Edit : Tacklife was the first I mentioned. Had to unscrew the tailcap on this one to expose the socket but not the Wuben.
you would have to tell the driver somehow to send the + current back, and not send it through the light and driver circuitry.
though a side switch could do that, have a ‘charge’ setting, or the firmware could control that path.
or the usb jack could control a switch that would divert + back to the tail.
the problem is, usually when you close the switch, that + current goes to the driver to turn the light on, or whatever.
you don;t want the light to be randomly on, when you are charging.
Interesting
As I empirically found out, all the charging circuits that I saw are the same, ie, built-in CC/CV circuitry that’s meant to go right across the cell itself. Some wall-warts do that, too (listed as “4.2V out”). The only differences being the dimensions of the connectors/contacts.
Only scary thing to me is whether/not the contacts on the light are protected in any way. Having “live” contacts fully exposed, even if, say, the center is recessed, is a Bad Idea. Dropping on fuzzed steel-wool, a pile of keys, or just dropping into saltwater, could end up with a pretty horrendous current-dump from the cell.