Ever notice how your phone doesn't always pull the full 1 amp from that 1000 milliamp charger? There is a reason for this. USB charging is limited to 500 mA. If the charger doesn't tell the phone that it is not a USB port, it will not draw more than 500 mA. How does the charger tell the phone that it is not a USB port? By shorting the two data wires. If the phone sees the data pair shorted, then it will draw all of the available power from the charger.

I have experienced this problem with Griffin chargers--which are great, but when used with a standard data cable, they only charge at 500 mA.

There are two solutions to this problem. (1) you can get a "Charge Only" micro usb cable which has the data pair shorted; or (2) you can get a Satechi Smart Adapter, which is a little plug device that goes between the charger and the standard cable and has the data pair shorted. I have tried both and both options work with my Galaxy Nexus.

Satechi: (available on Amazon and inexpensive)

The Satechi adapter is a good option if, like me, you already have a bunch of micro usb cables.

Disclaimer: Info in this post based on my Internet research. I am not an electrical engineer.