Pro Trinket is a perfect solution for small project but often times you need to power it wirelessly. So instead adding a couple extra boards to your project for powering through and charging a LiPoly/LiIon battery, this little PCB sits right on top of the Pro Trinket. Connect the battery through the JST connector and your project runs on the battery. It automatically charges the battery when you connect the USB cable to the Pro Trinket. Sweet Huh?
Ideally this Backpack is designed for 3.3V Pro Trinket but can run fine with 5V as well. You can also add an on/off switch with the 2 provided holes.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. The charge current is 100mA by default, so it will work with any size battery and USB port. If you want you can easily change it over to 500mA mode by soldering closed the jumper on the bottom, for when you'll only be charging batteries with 500mAh size or larger.