I am a little less than a week into my Apple iPad 3G experience and I am, for the most part, very impressed with this little piece of technology. One this I have noticed, however, is whenever I attach it to a computer via USB, the screen says that it is not charging. The same goes for when I attempt to charge it using my new Powermat 2x Charging Mat (reviews of this will be coming soon). The funny thing is, eventually it DOES charge. Today I found an article on this topic from Gizmodo, that seems to explain what’s going on.
According to the article, Consumer Reports was told by Apple support that the device is designed to charge using the included wall plug (I don’t remember getting one of those…). It goes on to cite an “anonymous Apple employee”, who told them that the iPad won’t charge using most USB ports because it requires 10W of power to charge it. If my math is correct, a standard USB port provides 2.5W of power so, yes, that would be a problem.
My experience, as well as some others I have run across on the blogosphere, it that the iPad will charge plugged into a USB port once the screen shuts off. It just takes longer.