There is a difference between the interface voltage of the USB interface and the power adapter, and the ordinary power adapter is 5V. But now due to the emergence of the fast charge interface, there is 9V, 12V voltage, and the USB interface only 5V a voltage.
The current is also different, and the USB interface is 5v1A.
Not as good as a power adapter. But at least in these years of use, I didn't find that this gap really made a difference to the battery. After all, cell phones don't require much electricity. pad is not the same, with the computer usb many times the charge is super slow, or even can not be charged.