I am using a MacBook Pro Retina 15-inch (Mid, 2015) running macOS Catalina 10.15 Beta (19A558d).

I want to use an external USB-C SSD drive (512GB) to use Windows To Go and store other files. Since my MacBook Pro only has type-a USB ports I also bought a USB type-c to type-a adapter.

However, my MacBook Pro does not recognize the USB-C drive, not in Disk Utility, not in BootCamp Windows, not in System Report, or anywhere else I've checked. What's more, the light on USB device is not blinking, which might infer that the device has no power.

So far I have:

  • ensured the MBP is full charged and also tested while connected to AC power
  • tested the SSD USB devices on my phone (which has a USB type-c port), and it powered up and was recognised fine
  • tested the adapter by connecting it to my Surface Pro 6, and everything works fine
  • tested the adapter on my MBP but with a USB-C flat drive instead and everything works fine

Consequently, I think the MBP is not giving enough power to power up the USB-C external drive.

Can anyone offer a suggestion on how I may get the USB-C external drive to work with my MBP?

P.S. I found a similar question here.

  • Hi and welcome! Please see tour for a quick tour to the site. nice find the related question. Can you follow the steps in those comments & answer(s) and post the findings using edit. Otherwise you'll see the same comments here anyway. (notify me by @ankii)
    – anki
    Commented Sep 22, 2019 at 3:43
  • Thank you for the notifying. I suppose my problem is more complicated, since I have an USB-C to USB-A adapter connected, and my USB SSD is not a SATA one.
    – Blanker
    Commented Sep 22, 2019 at 7:34
  • Is the MacBook connected to a power supply when you do this? Commented Sep 22, 2019 at 8:56
  • Yes, it is connected to the AC power and fully charged. If the power to USB device is not enought, I think it might be manipulated by the masOS. When using another USB device with the adapter, the System Report shows the current power is 900 mA. I have no idea who to check this value on Windows, otherwise I might know how much power it is required to mount the disk.
    – Blanker
    Commented Sep 22, 2019 at 10:05

1 Answer 1


Since you're using a Beta version of Catalina it is always possible that this issue could be resolved by the final release version of Catalina.

However, assuming this is purely related to a hardware limitation with your current setup, the only way to try and resolve it is to get enough power to the external SSD. As such, you have the following options you could try:

  • If the external USB-C drive has the option for its own power source connected to it, then doing that will solve the problem
  • You could opt for an adapter that connects from two USB-A ports to one USB-C port, thereby combining the power from two ports to provide enough for the external drive
  • You could use a powered external USB hub or dock (i.e. connect the USB Hub to the MBP and then connect the USB-C drive to the hub)
  • Double-check that the adapter you're using is actually capable of passing enough power through


  1. While there are many cables/adapters that can utilise the power from two USB-A ports to a single USB-A port, I'm not sure if one exists that goes to a single USB-C port - so you may need a second adapter to get this to work.
  2. Only you can decide if the expense of using a hub or dock is warranted in this use case.
  • Thank you for making my questions more understandable and also for your suggestions. But I think these methods are not that decent... I mostly use Windows To Go for convenience without bring so much stuff alone with me. I use the same adapter with the USB SSD, and it works pretty well on my Surface Pro 6 even without AC power connected. Therefore, I also think it might be a Beta system related issue, so I will have a try on other MacBook.
    – Blanker
    Commented Sep 22, 2019 at 7:28
  • Yes, testing on another MacBook not running a Beta OS would be good.
    – Monomeeth
    Commented Sep 22, 2019 at 22:55

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