I'm looking to limit the amperage output Windows gives to usb devices through a certain port. I'm finding Windows is providing 500mA to devices that only operate on 100mA or lower, which is consuming excess battery life.

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The device on the left is my USB mouse which hasn't shown up. It only requires 50mA to operate, and it is being provided 500mA.

1 Answer 1


USB ports are voltage sources, not current sources. That means the actual current drawn is exactly how much a device needs for the voltage to stay at 5 Volts. No excess current will flow.

The current values shown are in the USB descriptors, enabling the OS to detect over-current situations (too much high power stuff plugged) in bus-powered hubs.

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