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PCB files for the Adafruit Charger BFF for QT Py.
Format is EagleCAD schematic and board layout
Is your QT Py all alone, lacking a friend to travel the wide world with? When you were a kid you may have learned about the "buddy" system, well this product is kinda like that! A board that will watch your QT Py's back and give it the power and support to wander out past your USB port.
This little lipo charger is designed to fit onto the back of any QT Py board, and make it easy for portable powering. Simply plug any standard 3.7V/4.2V lithium polymer or lithium-ion rechargeable battery into the JST plug on the end. When powered by the USB port on the QT Py, the charger kicks in and will charge up the battery at 200mA max rate. You'll see the yellow LED light up when that happens.
When the USB is removed, the battery will reverse charge into the 5V port via a Schottky diode. You can turn it on or off with the built in slide switch as well.
A simple voltage divider on the cathode side of the diode and connected to pin A2 will let your firmware detect basic modes: if the voltage is over 4.3V, it is probably plugged into USB. If the voltage is 4.2V or below its probably running on the Lipoly battery and you can roughly determine the battery state.
We include some header that you can solder to your QT Py. You can also pick up an Itsy Bitsy short female header kit to make it removable but compact, you'll just need to trim down the headers to 7 pins long.
For use with Adafruit LiPoly/LiIon batteries only! Other batteries may have different voltage, chemistry, polarity, or pinout.
- Comes as an assembled and tested PCB
- Uses the 5V input via USB Type-C connector on QT Py
- For charging single Lithium Ion/Lithium Polymer 3.7/4.2v batteries (not for older 3.6/4.1v cells)
- 200mA charge current
Batteries and QT Py are not included.
Revision History:
- As of December 12, 2025 - We added two breakout pads for the on/off switch for an external switch if desired. We also updated the PCB with Adafruit Pinguin to make a lovely and legible silkscreen.
Adafruit invests time and resources providing this open source design, please support Adafruit and open-source hardware by purchasing products from Adafruit!
Designed by Limor Fried/Ladyada for Adafruit Industries.
Creative Commons Attribution/Share-Alike, all text above must be included in any redistribution. See license.txt for additional details.
