Delete comment from: Ken Shirriff's blog
You seem overly concerned with the voltage of the Apple adapters. The USB spec allows the supply voltage to vary between 4.4V and 5.25V, so a USB device has to be able to use these voltages. So the iPad power supply drooping down to 4.4V is not a problem.
Also the iPad supply is advertised as a 10W adapter and that's exactly what it delivers. It seems perverse to mark it down for living up to its specification. The power supplied is a USB nominal 5V, which is allowed to be as low as 4.4V.
Oct 31, 2012, 10:11:33 PM
Posted to A dozen USB chargers in the lab: Apple is very good, but not quite the best