I have one of these USB charging cables for my DROID Cellphone. It normally plugs into a 120VAC ADAPTER for charging my DROID CELL PHONE battery. Also one of my TABLETS gets charged this way as well...

I can also plug this into any of my four USB 12VDC charge ports in my F150 truck to charge my DROID CELLPHONE battery.
I have also plugged this into my COMPUTER USB port and I see my battery CHARGE DISPLAY on the DROID working normal...
This is also the same port I can use to download and listen to AUDIO PORTS from my DROID and TABLETS from my Truck Radio System
I can't say I have ever left my DROID on this COMPUTER USB port for a continuous battery charge but during the short times I am using it it does show the charge display being active...
????
Roy Ken