Currently Being ModeratedJul 22, 2012 8:48 AM (in response to sob8)
The key is that you note that "it started charging.....". But, it very likely stopped charging within a minute or two.
Apple does not publish a specification for the USB port, but maybe another user has tested to see what this might be. Good luck on that.
Whatever the actual output voltage might be at the USB port on the Express, it is not enough to charge the iPhone or iPad.
Currently Being ModeratedJul 23, 2012 1:29 AM (in response to Bob Timmons)
So I dug out my multimeter and tested the port. I have an old cable that is usb on one end and bare wire on the other end, so I plugged it into the Airport Express to test. 5 volts DC as expected, but only about 40mA. I thought that was pretty low for the mA so I tested a usb charger for a Samsung tablet that lists it's output at 2A. Sure enough the multimeter showed 2.25A, so I know the meter was working correctly. Would be nice to have a little more power out of the Airport Express usb.
Does anyone know if the newest Airport Express (802.11n v2) has more power output?
Currently Being ModeratedJul 23, 2012 5:19 AM (in response to sob8)
I don't know if the "new" Express actually has any more output....I doubt that it does....but I do know that the 2 samples that I have of the product will not charge the iPhone or iPad.
I have not tried using a powered USB hub as a charger. You might want to give that a try if it is important for you to be able to charge a mobile device from an AirPort.
Currently Being ModeratedJan 29, 2013 2:59 AM (in response to sob8)
The first and second generation Airport Express had a higher USB power output. I used to charge my iPhone 2g off of it, as well as run USB powered speakers off of it (which was nice because it only required one power outlet to stream music - the first Airplay speakers!). But later generations lowered the spec, and trying to power speakers would cause clipping if you turned the volume up too high.
Unfortunately all the old ones had PSU problems, so it's very hard to find them around anymore. Probably the lower USB output was necessary to fix that problem. I frankensteined a couple of mine to keep them going for a while, but I just lost my last one a few weeks ago.