# Adafruit LiIon or LiPoly Charger BFF Add-On for QT Py
## Overview
Yellow: 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.
[Is your QT Py all alone](https://www.adafruit.com/?q=qt+py&sort=BestMatch), 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](https://www.adafruit.com/product/4174), 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](http://www.adafruit.com/products/258) 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.
- [Next Page](https://learn.adafruit.com/adafruit-qt-py-charger-bff/pinouts.md)
## Primary Products
### Adafruit LiIon or LiPoly Charger BFF Add-On for QT Py
[Adafruit LiIon or LiPoly Charger BFF Add-On for QT Py](https://www.adafruit.com/product/5397)
[Is your QT Py all alone](https://www.adafruit.com/?q=qt+py&sort=BestMatch), 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...
In Stock
[Buy Now](https://www.adafruit.com/product/5397)
[Related Guides to the Product](https://learn.adafruit.com/products/5397/guides)
## Featured Products
### Lithium Ion Polymer Battery Ideal For Feathers - 3.7V 400mAh
[Lithium Ion Polymer Battery Ideal For Feathers - 3.7V 400mAh](https://www.adafruit.com/product/3898)
Lithium-ion polymer (also known as 'lipo' or 'lipoly') batteries are thin, light, and powerful. The output ranges from 4.2V when completely charged to 3.7V. This battery has a capacity of **400mAh** for a total of about 1.9 Wh. If you need a larger (or smaller!)...
In Stock
[Buy Now](https://www.adafruit.com/product/3898)
[Related Guides to the Product](https://learn.adafruit.com/products/3898/guides)
### Lithium Ion Polymer Battery - 3.7v 500mAh
[Lithium Ion Polymer Battery - 3.7v 500mAh](https://www.adafruit.com/product/1578)
Lithium-ion polymer (also known as 'lipo' or 'lipoly') batteries are thin, light, and powerful. The output ranges from 4.2V when completely charged to 3.7V. This battery has a capacity of 500mAh for a total of about 1.9 Wh. If you need a larger (or smaller!) battery,
In Stock
[Buy Now](https://www.adafruit.com/product/1578)
[Related Guides to the Product](https://learn.adafruit.com/products/1578/guides)
### Lithium Ion Polymer Battery with Short Cable - 3.7V 420mAh
[Lithium Ion Polymer Battery with Short Cable - 3.7V 420mAh](https://www.adafruit.com/product/4236)
Lithium-ion polymer (also known as 'lipo' or 'lipoly') batteries are thin, light, and powerful. The output ranges from 4.2V when completely charged to 3.7V. This battery has a capacity of 420mAh for a total of about 1.55 Wh. If you need a larger (or smaller!) battery,
In Stock
[Buy Now](https://www.adafruit.com/product/4236)
[Related Guides to the Product](https://learn.adafruit.com/products/4236/guides)
### JST-PH Battery Extension Cable - 500mm
[JST-PH Battery Extension Cable - 500mm](https://www.adafruit.com/product/1131)
By popular demand, we now have a handy extension cord for all of our JST PH-terminated battery packs (such as our LiIon/LiPoly and 3xAAA holders). One end has a JST-PH compatible socket, and the other end has a matching plug. Between the two, 500mm of color coded wire. Handy for wearable...
In Stock
[Buy Now](https://www.adafruit.com/product/1131)
[Related Guides to the Product](https://learn.adafruit.com/products/1131/guides)
## Related Guides
- [Tiny LED WiFi Companion Cube](https://learn.adafruit.com/tiny-led-wifi-cube.md)
- [BLE Beacon NeoPixels](https://learn.adafruit.com/ble-beacon-neopixels.md)
- [Video Nub Shank: ESP32 QT Py Composite Video Injector](https://learn.adafruit.com/video-nub-shank-esp32-qt-py-composite-video-injector.md)
- [Wireless LED Juggling Balls with ESP-NOW](https://learn.adafruit.com/wireless-juggling-balls-esp-now.md)
- [NeoPixel Star Crown with WLED](https://learn.adafruit.com/neopixel-star-crown-with-wled.md)
- [Wireless ESP32-S2 Touch Screen Controller for Pure Data](https://learn.adafruit.com/wireless-esp32-s2-controller-for-pure-data.md)
- [Icicle Crown with Pebble Pixels & WLED](https://learn.adafruit.com/icicle-crown-with-pebble-pixels-wled.md)
- [Traffic Light Conference Badge](https://learn.adafruit.com/traffic-light-conference-badge.md)
- [3D Scans for Low Poly Statues](https://learn.adafruit.com/low-poly-3d-scans-for-3d-printing.md)
- [One Key: Single Button Bluetooth Keyboard](https://learn.adafruit.com/onekey.md)
- [Cheekmate - a Wireless Haptic Communication System](https://learn.adafruit.com/cheekmate-wireless-haptic-communication.md)
- [LED Noodle Lantern](https://learn.adafruit.com/led-noodle-lantern.md)
- [Adafruit LSM6DS3TR-C 6-DoF Accel + Gyro IMU](https://learn.adafruit.com/adafruit-lsm6ds3tr-c-6-dof-accel-gyro-imu.md)
- [reef-pi Guide 2: Power Controller](https://learn.adafruit.com/reef-pi-power-controller.md)
- [AFMotor Library Reference](https://learn.adafruit.com/afmotor-library-reference.md)