I have no idea what the amperage is since this thing is literally nothing more than white slab of plastic with a USB connector inside. I got it at a local electronics shop for cheap.

For what it's worth, I've seen similar behavior with a number of other car chargers.

Still, the USB charging standard seems to allow for increasing the voltage:
Quote:
All devices that plug into a USB port must start out drawing no more than 100mA. After communicating with the host, the device can determine if it can take the full 500mA.

The core question is whether (a) anybody makes a car charger adapter that does this properly and (b) whether my phone would take advantage of this or not.