Power Bank - 20 000mAh

A custom case for the DYI power bank. Can fit cells up to roughly 20000mAh. Designed to fit specific PCB (see list of materials below) and any battery cells with dimensions up to 108x72x26mm.

USB-C input/output, USB-A output only, 18W max, supports PD/QC/AFC/FCP/PE/SFCP. 

List of materials

• 10x M3x8mm screw
• 10x M3 4.5mm(OD), 3mm(length) heat insert
• power bank PCB - https://www.aliexpress.com/item/1005005373508306.html
• battery cell(s) - e.g 2x https://www.aliexpress.com/item/1005002987841434.html
• wires for connecting the battery to the PCB (use thicker ones)
• few pieces of high-density foam and double-sided tape to fix the battery in case

Tools required

• a screwdriver 
• soldering iron to press heat inserts into the model
• scissors and/or knife for double-sided tape and foam
• sanding paper (optional)

Print settings

• PETG or other heat-resistant material
• 0.2mm or smaller layer height
• 0.4mm nozzle
• no supports are needed in the default orientation
• default infill
• use the emboss text feature (one layer deep) in PrusaSlicer and manual color swap to emboss text with the battery capacity

Assembly instructions

Disclaimer: you should know a thing or two about soldering, batteries and the potential risks involved. I'm not providing diagrams and guides on how to solder the circuit together or claiming the materials used are 100% safe. You may want to look into materials such as https://www.prusa3d.com/en/product/prusament-petg-v0-jet-black-1kg/.

Before assembly, you'll need to press in the heat inserts. Be careful not to hold the soldering iron on them for too long as the sides are pretty thin, and any excessive melting may be visible outside the case. 

The battery/ies should have a little space around them to accommodate potential expansion. I used double-sided tape and a few pieces of high-density foam to fix them in place. (see the attached pictures). Do not use an excessive amount of double-sided tape on the battery itself, as it may be difficult to remove it later.

Before inserting PCB, put a printed button in place. Fit with PCB should be just right, if not, scrape a bit of plastic from the printed button indent. For attaching the PCB to the case, you can use strong double-sided tape, a bit of glue or use two pieces of flexible material on its sides so that once the lid is screwed, the PCB is lightly pressed into place. I used TPU squares protruding about 1mm from the bottom part of the case and a small piece of double-sided tape to hold them in.

Depending on your printer's precision and precision when inserting heat inserts, you may need to sand the faces to achieve a gapless fit.

Screws should not be screwed in too tightly to prevent the lid from cracking. It's plastic, after all.