I found the stock USB cable does not charge while connected to the computer, but worked well with the wall plug.
I had a friend give me a new cable that is at least twice as thick and it charges as good on the computer as it does in the wall, and as a bonus it is 6 ft. long so I leave it on my work computer and don't need to transport the charger every day.
So i guess the cable makes a difference, I had no Idea until I saw for myself.