- Ideally for use with the 3.3V Pro Trinkets & ItsyBitsy
- Charging is performed in three stages
- Will work with any size battery and USB port
If you have an ItsyBitsy or Pro Trinket you probably know it's the perfect little size for a portable project. This LiPoly backpack makes it really easy to do! Instead of wiring 2 or 3 boards together to make a charging system, this little PCB sits on top of the PCB and allows a LiPoly/LiIon battery to plug in. When the Pro Trinket or ItsyBitsy USB port is powered, the battery is recharged automatically. Unplug the USB port and the microcontroller will switch over to the rechargeable battery.
Ideally, this backpack is for use with the 3.3V Pro Trinkets & ItsyBitsy, so that the battery voltage (3.7V-4.2V) will get regulated down to 3.3V on the board. Solder the backpack on with the extra long header so that it can still plug into a breadboard, or clip the long header leads short afterwards for a slim package.
If you want to add an On/Off switch, that is really easy. The two 0.1" holes with a box around them are the battery output line. Carefully cut the trace between them with a hobby knife and replace with two wires from a switch like this slide switch, or this pushbutton one. Charging is performed in three stages: first a preconditioning charge, then a constant-current fast charge and finally a constant-voltage trickle charge to keep the battery topped-up.
Assembled and tested
100mA charge current, adjustable to 500mA by soldering a jumper closed
Size: 15mm x 17mm x 2mm / 0.6" x 0.7" x 0.08"
Height w/ JST: 7mm / 0.3"
For use with Adafruit LiPoly/LiIon batteries only
Batteries and Pro Trinket or ItsyBitsy not included