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+---
+description: "Laptop power bank"
+created: 2022-11-13
+---
+
+![Power bank finished](main.jpg)
+
+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](/Electric longboard)
+
+## Parts list:
+  - [20V USB C PD Bidi buck boost converter](https://www.aliexpress.com/item/1005004629297118.html)
+  - [18650 holders](https://www.aliexpress.com/item/1005002749793325.html)
+  - [Heatsinks](https://www.aliexpress.com/item/32969500753.html)
+  - [USB C PD tester](https://www.aliexpress.com/item/1005002767097993.html)
+  - [4S li-ion BMS with balancing](https://www.aliexpress.com/item/1005001916022803.html)
+  - [Battery capacity display](https://www.aliexpress.com/item/4000448424977.html)
+  - Samsung-30q 18650 li-ion batteries (got these from a trustworthy local seller)
+
+## Plan
+
+![Battery pack back](battery_pack_back.jpg)
+![Battery pack front](battery_pack_front.jpg)
+
+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
+
+![Electronics](electronics.jpg)
+
+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.
+
+![Battery pack back 2](battery_pack_back_2.jpg)
+
+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](https://www.aliexpress.com/item/1005004508048246.html)
+maybe for a future powerbank.
+
+## Designing enclosure
+
+![Battery pack back 2](3d_model_plan.jpg)
+![Power bank 3D model](case_model.png)
+
+After learning [FreeCAD](https://www.freecadweb.org/), 
+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](/files/powerbank/POWERBANK.FCStd), [BackPart](/files/powerbank/POWERBANK-part1.stl), 
+[FontPart](/files/powerbank/POWERBANK-part2.stl),[Button](/files/powerbank/POWERBANK-button.stl)
+
+![Power bank 3D model](print.jpg)
+![Power bank 3D model](usb_c_connector.jpg)
+![Power bank 3D model](lcd.jpg)
+
+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.
+
+![Power bank finished top](finished_top.jpg)
+![Power bank finished bottom](finished_bottom.jpg)
+![Power bank finished lcd](finished_lcd.jpg)
+
+## 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
+
+![Laser cut node5.net logo](laser_engraved_node5.net.jpg)
+![Laser cut LCD](laser_cut_lcd.jpg)
+
+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.
+
+## External links:
+  - [youtube.com - BMS explanation video](https://www.youtube.com/watch?v=QNENyu97w2A)
+  - [youtube.com - GreatScott! PD module video](https://www.youtube.com/watch?v=_WI9Nwqvplo)
+