How to determine whether a USB socket is qualified for charging?

Question

More and more devices begin to take advantage of USB sockets as a charger, but sometimes a USB charger does not work because the socket does not have high enough power (output). This usually happens on a laptop, or USB sockets in the front of a desktop.

My question is how to determine if a USB socket is qualified for charging, besides exhaustive testing.

Thanks.

Answer 1

Dell notebooks (at least in their Lattitude line) have a small lighting bolt next to the USB label which indicates is a higher power charging port. I would hope other notebook manufactures do similar labeling.