USB is being implemented as a power connection standard more and more
these days, but you don't always have a computer on hand so how are you going
Charging Batteries From a USB Port – Battery University
Nov 25, 2016 ... Know the limitations when charging a battery with a USB charger. ... With 5V and
500mA available on version USB 1.0 and 2.0, and 900mA on USB 3.0, ... The two
shorter pins, 2 and 3, are marked D- and D+ and carry data.