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Power bank 20v USB-C PD
Created: 2022-11-13 | Modified: 2024-10-16
Laptop power bank
A DIY power bank with 20v USB type C power-delivery. I had a bunch of 18650's from a previous project, that were no longer in use... see Electric longboard
Parts list:
- 20V USB C PD Bidi buck boost converter
- 18650 holders
- Heatsinks
- USB C PD tester
- 4S li-ion BMS with balancing
- Battery capacity display
- Samsung-30q 18650 li-ion batteries (got these from a trustworthy local seller)
Plan
The battery pack is designed as a 4s 3p pack (4 in series and 3 in parallel). So the batteries will be connected altering + and - every 3 cells.
Component testing
I've tested the electronic components by connecting the bare minimum of batteries 4s 1p. You have to connect power the the board once, and then it works. I used a USB c PD trigger board to test the PD capability. It works, but the buck boost converter coil gets very hot, even with the heatsink on. Will have to use a bigger heatsink for it. Possibly on the back, though i need to insulate 2 points on the back, that aren't part of the ground plane, like the rest of the back. The mosfets on the BMS don't heat up, could probably go without the heatsinks. I also need to design a case and 3D print it. The setup works but i'm worried about a short before the BMS. So i will probably redo the wiring.
Redid the wiring with the lessons learned during testing, and based on feedback from others. The Bi-Di module only seems to heat up when stepping down the voltage a lot, i think the current cooling will be adequate.
Someone just showed me an even better, but more expensive board: 100W PD and 120W DC power bank module maybe for a future powerbank.
Designing enclosure
After learning FreeCAD, i designed and 3D printed a case. It's designed to use a transparent acrylic as the top and bottom. You can download the model files here: TODO Add files FreeCAD Model, BackPart, FontPart,Button
Printed the case. The fit seems great I mounted the screen with some double sided tape, some screws that i heated up with my soldering iron, and some glue. I also shortened the button on the screen and put in a 3d printed button. Seems to click OK, and it's recessed a bit, so it won't be turned on accidentally.
Future ideas
- I think the screws are too close to the edge, so i got a new idea. 3D print a cover out of TPU for all the edges.
- It would be really cool to add a micro controller with power messurement, and an LED strip displaying the remaining charge.
Laser cut acrylic sheets
Some fellow hackers were super kind, to laser cut acrylic sheets for me, that has this cool reflective film that changes color based on the angle of the light. It features ventilation holes for the PD module and engraved text. It's way more precise, and the side of the cut is super clear.