If I have an ac adapter that has a USB port on it and I plug a four port USB hub into it, can I simultaneously charge four USB devices? Or… will I rip the fabric of spacetime?
Does your AC adapter put out enough current to charge all four devices simultaneously, or will the wall wart catch fire?
A standard USB port supplies 500mA. If the AC adapter with USB only supplies that 500mA to your bus powered 4-port hub, then no, you probably can’t charge four devices.
It sounds like you are talking about the Apple USB Power Adapter. I can’t seem to find the rated current online.
The Apple Ultracompact USB power adapter draws 150mA, so you could charge about 3 devices from one standard USB port. It’s designed to draw low power from the USB port though; most portable devices not designed to be charged off of USB usually want about 350-500mA, and 150mA may not be enough to trip the charge circuit.
Give it a try. Most modern USB devices these days are smart enough to tell you when there isn’t enough juice being supplied. For example, the front USB ports on my PC cabinet will only charge one device at a time. When I plug a blackberry and a Zune into it, they both tell me that they aren’t charging. I unplug one and the other starts charging.
I imagine your USB port will work the same way. Plug the AC adapter into it, plug in your USB splitter and plug in your devices. Check the power icon on your device and see if it shows that it’s charging and your question is answered.
FYI, they make some power splitters these days expressly intended to charge 4 USB devices and cell phones so perhaps you could just grab one of those instead of tasking these items that weren’t intended for it.