I'm considering charging a bunch of my iPod Touches with a USB 3.0 PCI add-in card.
In my research, I've found that USB provides 5 volts per device.
The differences come in charging speed. The more amperage, the faster a device charges.
USB provides "Unit Loads" of amperage for each device based on need.
USB 2.0 provides 100 milliamps per Unit Load, with a maximum of 5 unit loads per device. USB 3.0 provides 150 milliamps per Unit Load, with a maximum of 6 unit loads per device.
When a device is connected, it draws 1 Unit load until it asks for a higher amount based on need. That means a device can draw maximum 500 milliamps (or 0.5 amps) from USB 2.0 and 900 milliamps (0.9 amps) from usb 3.0.
The Apple wall charger for iPhones provides 1 amp (1000 milliamps).
Does that mean that an iPhone or iPod Touch plugged in to a USB 3.0 port will charge nearly as fast as one plugged in to Apple's AC plug?