Symptoms such as these could mean that a device connected to the USB-A , USB-C , or Thunderbolt (USB-C) port on your Mac isn't getting enough power:
- A message says that the device needs more power, the operation can't be completed, or USB devices are disabled until you unplug the device using too much power.
- An operation that requires more power doesn't work. For example, writing to disk requires more power than reading from it.
- The device doesn't turn on or isn't recognized by your Mac.
- Use your device as a self-powered device, such as by plugging it into an electrical outlet, if possible.
Self-powered devices get power from an electrical outlet or their own battery. Bus-powered devices get power from the device they're plugged into, such as your Mac.
- Reduce the total amount of power needed from your Mac by reducing the number of bus-powered devices connected to your Mac, or using more of them as self-powered devices.
- If your device is plugged into another device as part of a chain of devices, the other device might not be providing enough power or passing through enough power from your Mac. Plug your device directly into your Mac instead.
- Make sure that the port on your Mac and the cable you're using to connect it to your device both support the same or later USB specification as your device. For example, a device designed to support the USB 3 specification might not get enough power when plugged into a USB 2 port or cable.
- Try a different cable, in case the cable that you're using is damaged or defective. If you're using an adapter with your cable, the adapter could also be damaged or defective.
- If your device has software (such as drivers or firmware) that can be updated, make sure that it's using the latest software from the manufacturer. To get firmware updates for Apple accessories, update your Apple software.
- Make sure that your Mac is awake and started up from the Mac operating system. Some Apple devices can request extra power only when your Mac is awake or started up from macOS.
Learn more about USB power on your Mac
System Information provides additional detail about USB power on your Mac. Connect the USB device directly to your Mac, then select USB from the sidebar in System Information. For each USB device, System Information shows:
- Current Available: The default power provided by the port to which your device is connected.
- Current Required: The power needed by your device.
- Extra Operating Current: Mac computers and Apple displays introduced after 2006, when directly connected to certain Apple devices such as iPhone or iPad, can provide extra power over one or more ports. The Mac or display must be powered on and awake to provide this extra power. A Mac started from the Windows operating system doesn't provide extra power.
Learn more about the power available under each USB specification, such as USB 2 and USB 3.