Q: El Capitan shutting off USB power on MacBook Pro?

I've just installed the latest El Capitan update (10.11.3) and the problem is still happening. It's been like this for me since I first installed El Capitan last year. Before that everything was just fine.

I have an Early 2011 MBP 17" and it will charge my iPad Air 2 or iPhone 6 just fine after a reboot. However, once it has been to sleep, it won't charge, or will charge them very slowly. I've even seen it discharge the iPad.

To answer kilograham's question above, my symptoms are exactly the same if I connect my devices directly to the MBP or to a Thunderbolt. The problem is always the same regardless of direct or indirect connection - after a reboot and before sleep - charging is fine. After a sleep - no charging or slow charging until next reboot.

I've also reported this to Apple. Given the range of devices being affected you would have expected a fix by now. It's really starting to get OLD....

Same here - Power on USB ports is lower and charging is unbearably slow.  I simply do not understand why Apple is not fixing this issue that they created in this "new" El Capitan release.  It was never a problem before this release. 

Another report of the same problem. It also happens to me while the computer is awake; devices will randomly disappear.

I have the following devices connected (these are the EXACT same devices I had hooked up prior to upgrading, which NEVER had a so much as a whisper of a problem with USB):

Sharkk Wireless Mouse

Microsoft Sculpt Keyboard

Kensington Displaylink adapter.

I've tried SMC reset, and every other fix I could find in the various threads about USB issues in el ap.

Apple broke something with EL Capitan.

Just wanted to add my name to the list of affected users.

I have a kingston HyperX SSD usb drive that used to work flawlessly. Now it disconnects 2 mins after connection. I run VM Ware fusion to run some windows applications that I need for work. It is now unusable.

Fix this Apple. GRRRR

I can confirm that changing the energy saver preferences does not fix this.

On a 2015 MB Pro with El Capitan, with an external SSD attached, with never sleep, never spin down drives etc. selected.

The drive is still randomly disconnected by the operating system whilst connected to the power brick, and whilst accessing, the OS doesn't pick up an eject event, but shows a "this drive was disconnected" event, so it seems the power for the USB port was dropped.

The same drive works perfectly when running Windows 10 on bootcamp on the same machine, using the same USB port and same USB cord.

Points to an issue with El Capitan's USB power management?

I got  the same problem on MBP 15", 2015. My USB audio device works well on Mac OX X 10.10, but on 10.11 it stops working after several minutes (sometimes after several seconds).

And the latest update (10.11.4) doesn't resolve my problem.

I got the same problem on a Mac Mini late 2012 and the last 10.11.4 didn't solve it...

As a test, I stopped using VMware fusion for a while, and I actually haven't had a problem since. No more devices randomly dropping out. I'm on Fusion 6. I know Fusion 8 is out, with support for el capitan, so perhaps that would fix this problem, but it's a good amount of money to spend on a test.

Unfortunately 10.11.5 doesn't solve my problem.

This was related to having a Parallels virtual machine running in my case. Suspending the VM before sleeping seemed to keep the USBs powered on my macbook.

I apologise if this is not exactly the right thread for this, but felt I needed to comment and say that I think you might be on to something with your USB power management comment. I believe it IS an issue with either the USB power management or a driver issue in OS X that may make it look like a hardware issue that some have suspected. For the record, I have a 2015 15" rMBP that I have both loaded with both OS X El Capitan and Windows 10 and often experience the dreaded connection and disconnection of iDevices, plus the odd USB3.0 HDD drop off in OS X. Plus I have a 2012 Mac Mini with El Capitan, which is rock solid when it comes to USB connected devices, iDevices and HDDs.

A condensed version of my troubleshooting journey…

Within a day or two of getting my new rMBP, I discovered the bizarre but regularly reported connection/disconnection problem with iDevices, coming from a 2011 15" MBP, I found this quite strange. Discovering several forum threads on this particular issue, I continued troubleshooting, even so far as to roll back to Yosemite and discovered the problem was still present. I was thinking at this stage it might be a hardware issue. Continuing my adventure, I discovered that an almost fully charged iDevice connected with no issue to the rMBP, no matter what USB port it was plugged into. Thinking that I was on to something, I deliberately drained my iPad battery, got it down to about 20% then plugged it in to the same port it worked perfectly from earlier, the connection kept flapping, so did the other port. So this was my first thought around insufficient power, but how to solve it. It was later on down the track I found external USB 3.0 drives randomly disconnecting, not all the time, but enough to become frustrating. I was reluctant to believe my new MacBook had a faulty logic board already, so I persisted with the issue by swapping ports till I got one that connected, all while being completely puzzled as to why this was happening on an almost $4000 piece of hardware.

Later on down the track for fun, I decided to take advantage of the free Windows 10 upgrade to see what it was like on a rMBP while still having OS X for my normal day to day. Once I got Windows 10 bedded in, I forgot about it for quite a while and frustratingly put up with the frequent USB issues in OS X until one day in OS X, no USB port would accept an iDevice, PRAM and SMC resets didn’t help, I started to worry. I booted into Windows to see if Device Manager was picking up any hardware issues, low in behold my still connected 15% charged iPad was appearing in the device list, I checked the battery indicator on the iPad, it was showing up as connected (it was on silent and didn’t realise it actually connected) and was charging quite happily. What… the…

As I write this today, my low charge (20%) iPad refuses to connect and remain connected in OS X, but reboot into Windows 10, it will connect and remain connected and charging with no issue whatsoever from either USB port.

Additional tidbits I have discovered on the net and conclusions I have come to.

• Some people have reported connecting a powered USB hub between an iDevice and the rMBP works around the connectivity issue - Haven't tried it myself, I have one, but I suspect it will work.
• Low powered iDevices will refuse to hold a connection (USB power brown out?). 80% charged or fully charged iDevices connect without issue and will continue to charge the device - Tested extensively and it’s the only way I can connect an iDevice to my rMBP.
• Having the power brick connected makes no difference - It didn’t on a 2011 MBP, it doesn’t on a 2015
• HDD disconnections are obviously due to power cutout, not communication issues - Mac OS reports disk was removed without being ejected…

So in summary, I firmly believe there is either a driver issue in OS X or a system configuration level issue. Because OS X is installed from the same generic installer package from the App Store, it's obviously tailored to the underlying hardware during setup. There must be a specific configuration for the Macbook Pro hardware and another for say an iMac and Mac Mini, each of those profiles for desktop Macs must have some different USB power profile configuration compared to a Macbook  which I assume is tuned for power reasons. Its for this reason I believe this power tuning on a laptop is the reason why we see these problems.

So, I genuinely believe the actual issue is a software driver problem in OS X, not a hardware issue because bootcamp Windows 10 can clearly use the ports properly and provide sufficient power and keeping devices connected.

While this is not a solution, it is perhaps a good way for others to test their hardware in bootcamp to see if they experience the same issues, from there it might take a Mac OS X guru smarter than I to figure out a way to escalate this to Apple and to help point their engineers in the right direction to solve the problem once and for all. Or someone to go in and make their own fix that can benefit the community.