So for the first time ever I've plugged my iPhone into my MacBook Air today to use iTether. Despite my MacBook Air running on battery I notice that my iPhone believes it is getting charged. This is going to drain my MacBook Air's battery . I haven't plugged my iPhone in to be charged, I've plugged it in for data. Is there anyway I can stop this? All I want the USB connection to be doing is transmitting data to/from my iPhone. I want to turn off the 500mA of power that the USB port has, make it unpowered if you see what I mean. Any ideas?