USB ports are just not capable of putting out high amps.
As an anecdotal example my HTC Sensation requires 1 amp to charge fast. When it is dead I plugged it into my USB ports in the car, and it would not revive (stayed dead) even within 15 minutes the milliamps put out by USB are just too low.
When I plugged in the device above to my car inverter the phone came to life and reached 10% fairly quick.
A device like:
http://www.amazon.com/gp/product/B004QDXMHU
is one of the best ways to charge your iPad or any current hungry device. With the swivel on this one and the pass through I like it when I plug in at a bus station, plane terminal or doctor's waiting room because others can plug in "on top of me" and charge.
http://www.amazon.com/product/B004QDVCT0
Is even cooler: 2 USB ports and 3! 120v pass throughs. I will get one of these 2.
You're right. It will charge but not indicate it is doing so. I believe the term is "trickle charge". However the cord for the iPad and the iPhone - the cord part with the USB end - is exactly the same. The bricks are different which plug into the wall.When I'm in a pinch, I charge my iPad via the USB plugged into the computer/laptop. Some charge is better than no charge and a dead iPad.Sharon H.
