Magnetic copper charging unit.
Using an old integrated flashlight USB charging board, I removed the momentary side switch, soldered on a 6mm x 2mm magnet to the centre positive contact with a positive pass through wire soldered directly to the side and a negative wire to the negative via on the board then soldered on a 6mm x 2mm magnet to the end of the positive wire.
I had to make a copper enclosure for the unit by cutting a piece of 22mm copper tube and bending it to a smaller diameter when closed together to fit into the copper body core.
Using solder paste and a dual jet flame lighter I applied the solder paste to the open ends, held the joint shut with grips and fused.
To make the enclosure stronger I cut a piece of 0.3mm copper sheet to the correct length to fit inside the thicker outer shell, applied more solder paste, held with the grips again to prevent the original joint re-opening and soldered all together.
The joint of the inner piece is opposite the joint in the outer piece for structural strength.
Some filing later...
Drilled out a 7mm x 2mm slot in the enclosure for the USB port and filed the hole into shape with a small diamond file.
The piece looks happy enough about this :-)
Made into rough shape.
Drilled a 1mm diameter hole for the charging indicator light near the charger board LED and filled with UV setting glue, filed out a slot in the enclosure opposite to the port for a thin copper strip to slide into.
Filed around 0.5mm off the edge of the charging board to fit the enclosure diameter, pressed the charger board into place and soldered to ground with the soldering iron. Also soldered another 4mm brass tube with double springs inside to the negative wire.
Potted components side with a layer of UV setting glue, some kapton tape covering the USB socket and JB welded the spring enclosure in place in line with the filed out slot.
The clear UV glue will carry the charging status indicator light to the external 1mm hole I drilled.
Potted the remaining spaces and positive contact magnet in place with JB weld & tidied up with fine wire wool.
Tip: Use BluTack or similar to remove any metal debris stuck to magnets.
Quick test: Blue :THUMBS-UP: 
The reason for the slot I filed into the case & sprung brass enclosure is to accommodate a magnetic copper negative connector, this can slide in position to fit different cell lengths although won't be used in the actual light, but it's there anyway.
The charging unit has a 1A maximum charge current.
Charge test: Red :THUMBS-UP: 
Showing how the unit fits into the inner core body. 
Added a 0.2mm thick copper skirt for a slight design change.
This is because the charging unit will sit further into the head of the light now with a chosen shallower reflector and give a snug fit in the inner copper tube.
I filed the outside of the charger unit enclosure to reduce the diameter by around 0.4mm, cut a section of copper sheet to size, filed edges smooth with the stones, applied solder paste, held in place with grips and fused together with the jet flame lighter, a slightly nervous moment doing this but it turned out fine :-)
