Quote:
Originally Posted by cybmole
I assume a mains charge delivers more amps than a PC usb link
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No.
At a minimum a USB port provides 100/150mA. All ports can provide this for even the most basic of devices.
All USB ports can increase this to 500mA (USB2) or 900mA (USB3) if the device communicates with the port.
Additionally, there's an optional USB Charging specification allows charging downstream ports (standard data ports) and dedicated charging ports to provide up to 1.5A for version 1.1 of the charging spec and up to 5A for version 1.2 (although only 1.5A if high speed data transfer is happening).
(All the above USB ports are 5v).
There's also a more recent 'USB Power delivery' specification providing up to 100W and higher voltages but I don't think it's very widely supported yet.
The biggest problem is that it's often difficult to find out what is supported by a particular device and port, although non-standard implementations from the likes of Apple can further confuse the issue.