My friend needed a battery for his bicycle light, and I found the Lithium charger module that's available in 12v, 9v or 5v.
Needed a case for it that can be attached to the bicycle frame, so I came up with this design that I created in Fusion 360.

He asked for the thumb screws, so you don't need a screwdriver to open when you need to get to the charging port.
He added a self-adhesive foam strip not to scratch the frame.
Use Velcro strips to attaches it to the frame.

Used PETG filament on a Creality K1 Max Printer for the Case with Tree Support

The water proofing rubber seals was printed with FILX TPR90 Filament that I get form FILX in Cape Town South Afrika
You can use TPU

Othe parts needed see pictures in BOM document
Dual 18650 lithium battery charger UPS module

4 x Insert M3 D 5mm L 5mm

2 x Hexagon Head Screw M3 x 12mm

4 x Countersunk Screw M3 x 8mm

2 x Hexagon Thin Nut DIN 439-2 - M3

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If you don't need it to be used outside, you can use PLA Filament

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If you don't need it to be waterproof and using it inside, then you can just print and use the Top cover and Bottom Boddy

Please add a comment and Photo when you print it

Regards

Case Dual 18650 lithium battery charger module waterproof

0.2mm layer, 3 walls, 40% infill