Microsoft Band version 2 utilizes quick-charging technology, so you can power-up a diminished Band battery pretty quickly.
If you want to improve the time it takes to charge the Microsoft Band, stick it into Airplane Mode (accessed through the Settings tile).
Airplane Mode turns off all wireless communication for the Band, including Bluetooth and GPS. By doing this, the Band no longer communicates with your smartphone, ensuring that it can concentrate solely on charging and not have to use battery to display every new notification that comes in.
This tip is not going to give you instantaneous charging capabilities, or improve charging times drastically, it can help.
P.S. Don’t forget to turn Airplane Mode back off when you’re done charging.