I am planning on building a quite large USB hub, which final use is to connect, charge and sync let's say 40 iPads. The iPad electrical specification from Apple states that each unit needs to have available 5v/2.1A from the USB bus power to charge fast.
I still don't know if I'm gonna build the USB hub from scratch or I'm gonna buy a few cheap hubs and bridge them together, but the main question is: if I need the devices just syncing, I need 500mA in each port, which means 0,5*40 = 20A.
Does that mean I can accomplish that by removing the +5v wire coming from the PC port (or placing a diode) and powering the same path with a massive 5v/20A power supply? Will this work as expected? Isn't there risk of "burning" the USB devices or the computer?