This is a powerbank !

It is designed to use four 18650 lithium-ion cells in parallel, providing up to 40 Wh on a single charge and supporting fast charging and USB Power Delivery.

Materials:

• 4× 18650 lithium-ion cells with similar capacity, health, and charge level. Mixing old and new cells can be dangerous.
• Charging/BMS module (Amazon or AliExpress)
• Wire (18 AWG / 0.82 mm² or larger)
• Glue (hot glue or epoxy)
• Optional : Kapton tape

Tools:

• Soldering iron or spot welder
• Multimeter
• Wire stripper

Print settings:

• PLA, ABS, PETG, you can use any rigid filament. Maybe TPU can work for the “Outside”, haven't tried it yet.
• 2 or 3 walls, don't really need more as there won't be any stress applied.
• Supports are not mandatory if your printer can bridge but it might make it look better.
• Be sure to place the seams away from the gap in the compliant mecanism or it may not work.

Assembly:

• Place the cells in their slots and glue them together. Make sure all cells have the same orientation (all positives on one side and all negatives on the other). The batteries must be connected in parallel.

• Solder the cells together using a spot welder (recommended) or soldering iron. Avoid heating the cell terminals for too long and be careful not to short-circuit them. Tape the terminals with electrical or Kapton tape to prenvent any short circuit.

• Measure the pack voltage with a multimeter (3.6–4.2 V depending on charge).
• Power the module alone and verify output is correct.
• Solder the wires from the battery pack to the PCB, making sure the polarity is correct.

• Test the module again under load.
• Place the board into the 3D printed part labeled “Inside” and fit the battery assembly into its slot.

• Ensure that the compliant mechanism on the “Outside” part moves freely.
• Glue the printed part, cells, board, and screen together securely.
• Press the assembly into the “Outside” shell. It should be snug, but you may add glue if required.

Tada! You now have a working battery pack!

Inspiration: 

This project was inspired by Shop Therapy’s model on Maker World, but redesigned from scratch to meet my needs.

Safety Warning:

Lithium-ion batteries can be hazardous (toxic, flammable, and potentially explosive). Handle with care.
Do not short-circuit, puncture, crush, or use cells that appear damaged or swollen.
I take no responsibility for injuries, fires, or damage that may result from building or using this project.

If you build this project, I’d love to see the result! Feel free to leave a comment or post a picture of the finished powerbank.

If you have any issues with the project, I’d be happy to help.

You can send me a private message if you need more information.