It turns out that the "Not Charging" message generated by some iPads
when charging via USB isn't really as bad as everyone thought. Erica Sudan confirmed what we had also encountered in a post on TUAW last week.
The iPad is a new kind of device that is stuck in limbo between being a large iPod/iPhone and a laptop so it ships with a power supply that is rated at 10 watts. That is considerably more wattage than the ones shipping with Apple's other handheld devices. However, it is a lot closer in wattage to the ones shipped with Apple's Macbooks. This means that the iPad needs more power to charge and unfortunately not all computer USB ports or hubs can provide what it needs to charge while it is awake.
We found out that the iPad will charge just fine on these low powered USB ports, but only after it goes to sleep and the screen turns off. We left an iPad in that state overnight and discovered it fully charged in the morning.
You can see additional Mac|Life coverage on this topic by reading iPad Charging: You're Doing it Wrong!
