To keep the battery topped up, charging is performed in three stages: a preconditioning charge, a constant-current fast charge, and a constant-voltage trickle charge. It has a default 100mA charge current and will work with any size battery or USB port. For charging batteries with 500mAh size or larger, it can easily change over to 500mA mode by soldering closed the jumper on the back. For use with Adafruit LiPoly/LiIon batteries only. Other batteries may have different voltage, chemistry, polarity, or pinout. Battery not included.