Boat Guy
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Q: Power output from USB ports

The manual for the Thunderbolt display says the USB ports can be used to charge iphone / iPad.  The new iPads (4th gen) come with a 12w charger.

 

What is the power rating on the Thunderbolt Display's USB ports?  Is it at least 12w?

Posted on Nov 16, 2012 11:33 AM

by JMAbeshaus,Solvedanswer
JMAbeshaus JMAbeshaus
Level 1 (35 points)
A:

USB is nominally 5 Volts. The maximum available current I looked up in system information (/Applications/Utilities/System Information.app) for my Thunderbolt Display which is given as 500mA. Power equals voltage multiplied by current which results in 2.5W.  

Posted on Dec 14, 2012 9:44 AM

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Q: Power output from USB ports

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  • by JMAbeshaus,

    JMAbeshaus JMAbeshaus Dec 13, 2012 5:47 PM in response to Boat Guy
    Level 1 (35 points)
    Dec 13, 2012 5:47 PM in response to Boat Guy

    The Thunderbolt Display's USB ports are 5 Volts and have a maximum current available of 500 mA (which equals 2.5 Watts maximum). This does not mean you cannot charge your iPad from the USB, it will just be much slower and require you to limit use on the iPad while charging.

  • by Boat Guy,

    Boat Guy Boat Guy Dec 13, 2012 10:30 PM in response to JMAbeshaus
    Level 1 (0 points)
    Dec 13, 2012 10:30 PM in response to JMAbeshaus

    Much slower indeed.  What is the source of your answer?

  • by JMAbeshaus,Solvedanswer

    JMAbeshaus JMAbeshaus Dec 14, 2012 9:44 AM in response to Boat Guy
    Level 1 (35 points)
    Dec 14, 2012 9:44 AM in response to Boat Guy

    USB is nominally 5 Volts. The maximum available current I looked up in system information (/Applications/Utilities/System Information.app) for my Thunderbolt Display which is given as 500mA. Power equals voltage multiplied by current which results in 2.5W.  

  • by Boat Guy,

    Boat Guy Boat Guy Dec 15, 2012 8:57 AM in response to JMAbeshaus
    Level 1 (0 points)
    Dec 15, 2012 8:57 AM in response to JMAbeshaus

    Yes, I understand P = IE, but didn't know I could find the available current data in the Sys Info.

     

    At only 2.5w, a full charge of the 42w/hr battery via the Mac or Thunderbolt monitor would probably take 18-24hs given the non-linear charge curve.  An overnight charge might put back half the capacity.

     

    Since the included iPad 4 charger puts out 12w, it is clearly the charger of choice!

     

    Thanks!

  • by Charlie Hedlin,

    Charlie Hedlin Charlie Hedlin Oct 13, 2015 7:41 AM in response to JMAbeshaus
    Level 1 (0 points)
    Oct 13, 2015 7:41 AM in response to JMAbeshaus

    I was looking for more detailed information on these ports and came across this incorrect information (and since it shows in google, yes I'm replying to an old thread). The display can certainly provide 1A to Apple peripherals.

     

    After plugging my iPhone into my thunderbolt display I opened system information and it has this (Extra operating current is what is important here):

     

    iPhone:

     

      Product ID: 0x12a8

      Vendor ID: 0x05ac  (Apple Inc.)

      Version: 8.02

      Serial Number: xxxxxxxxxxxxxxxxx

      Speed: Up to 480 Mb/sec

      Manufacturer: Apple Inc.

      Location ID: 0xa0110000 / 8

      Current Available (mA): 500

      Current Required (mA): 500

      Extra Operating Current (mA): 500