Increasing USB port Power Output
Apple USB 3.0 ports will output up to 1100mA if requested, USB 2.0 is limited to 500mA
You can check the current requirements for any attached device in Apple Menu &gt; About this Mac &gt; More Info (later macOS versions now labelled 'System Report…')... USB
I only have USB 2.0 ports on this machine, but see pic...