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Adafruit

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The Adafruit LiIon/LiPoly Charger BFF is a compact battery charging add-on designed to mount directly onto the back of any QT Py board. It makes portable pow...

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The Adafruit LiIon/LiPoly Charger BFF is a compact battery charging add-on designed to mount directly onto the back of any QT Py board. It makes portable power simple — plug in a standard 3.7 V/4.2 V lithium battery, and the charger handles the rest via the QT Py's USB-C connection.

When USB is connected, the charger tops up your battery at up to 200 mA (yellow LED indicates charging). When USB is removed, battery power feeds through a Schottky diode to the 5 V rail. A built-in slide switch lets you turn power on and off, and a voltage divider on pin A2 lets your firmware detect whether the board is running from USB or battery.

Key Features

  • 200 mA Charge Rate – Charges single-cell 3.7 V/4.2 V LiPo/LiIon batteries via USB-C
  • Automatic Power SwitchingSchottky diode routes battery power to 5 V rail when USB is disconnected
  • On/Off Switch – Built-in slide switch for power control
  • Battery Monitoring – Voltage divider on A2 pin for detecting USB vs battery power mode
  • Charging Indicator – Yellow LED lights during active charging
  • BFF Form Factor – Solders directly onto the back of any QT Py for a compact stack

Ideal For

  • Making any QT Py project portable with battery power
  • Wearable electronics requiring rechargeable batteries
  • IoT sensor nodes with battery backup
  • Compact prototypes needing USB charging capability

Package Contents

  • 1× Adafruit LiIon/LiPoly Charger BFF (assembled and tested)
  • Headers for soldering to QT Py
Warning: For use with Adafruit LiPo/LiIon batteries only (3.7 V/4.2 V). Do not use with older 3.6 V/4.1 V cells or batteries with different chemistry, polarity, or pinout. Batteries and QT Py board sold separately.

Jargon buster

Plain-language definitions for the technical terms used above.

Headers
Rows of connector contacts on a fixed pitch (commonly 2.54 mm) used to link a board to a breadboard, jumper wires, or another board. They come as male pin headers and female socket headers; when a module ships with pre-soldered headers it can be used straight away, whereas bare pads require soldering the pins yourself.
IoT
Short for Internet of Things, meaning physical devices that connect to networks or the internet to send data or be controlled remotely. It matters if you want projects such as connected sensors, remote controls or classroom data-logging activities.
LED
A light-emitting diode (LED) is a small electronic component that emits light when current flows through it in the correct direction. Because it only conducts one way, its polarity matters, and a through-hole LED must be soldered the correct way around to light up.
LiPo
A LiPo (lithium polymer) battery is a rechargeable lithium battery widely used in portable projects because it is light and compact. LiPo cells need correct charging circuitry and careful handling to stay safe, so equipment that supports LiPo generally includes charging or protection hardware suited to that battery type.
schottky
A Schottky diode is a type of diode with a low forward voltage drop and very fast switching. It matters when choosing parts for power protection, voltage regulation, or high-speed circuits because it wastes less power than many standard diodes but usually has higher reverse leakage and lower voltage ratings.
Schottky diode
A diode type with a low forward voltage drop and fast switching behaviour. It is useful when you want less power loss or quicker response, such as in battery-powered circuits, switching supplies, or reverse-current protection.
TOPS
TOPS means trillions of operations per second, often used to describe AI accelerator performance. It helps compare whether a computing module is suited to lightweight image recognition or more demanding neural-network workloads.
USB-C
USB-C is a small, reversible USB connector that can carry power, data and, on some devices, video over a single cable. The same connector can range from charging only to high-speed data, so the functions a given port actually supports vary.

Related Tutorials

Free guides on learn.littlebird.com.au

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