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What is the maximum current draw from the USB ports?

Discussion in 'Model S: User Interface' started by Barry, Jun 27, 2016.

  1. Barry

    Barry Member

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    And is it on the same circuit/fuse as the cig lighter plug?
     
  2. ddimit

    ddimit Member

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    I believe the Spec for the Port is 500ma max.
     
  3. BrokerDon

    BrokerDon Member

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    I don't know what the our 2015 Tesla P85D's USB outlet amperage is but I've charged both my 2.1A iPad Air 2 and iPhone 6 Plus at normal charging rates... So I'm surmising our Tesla's USB ports are capable of 2.1A
     
  4. scottm

    scottm Active Member

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    I wonder if you connected USB cable from port 1 on Tesla A, and other end to Tesla B port 2.... if car A would slowly charge car B ... ;)
     
  5. BertL

    BertL Active Member

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    I have not measured it myself, but older threads and external websites indicate for pre-refresh MS, one USB port is 2.1A while the other is 1A. Which one is which is the luck of the draw based on how the cable is connected during build.
     
  6. Barry

    Barry Member

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    Thanks all
     
  7. scottm

    scottm Active Member

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    If you insert your USB flash stick in a port and go to media, you will see USB1 if that port you chose happens to be USB1. And I guess that's the higher power one. Remember that port for charging devices.
     
  8. supratachophobia

    supratachophobia Active Member

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    Well that's basically false. The USB numbering is based on the order in which media is plugged in. So if I plug a usb sick it, it shows up at usb1. Then if I plug my ssd in, usb2-5 join the list. If I switched the order, the ssd would be 1-4 and the lone stick would be usb5.

    Back to topic, 2 amps is what I've heard. I've run the ssd plus 4 usb sticks on a non powered hub and everything worked great. There are apps for measuring draw on cell phone charging. You could try taking a reading and see if it hits 2amps. And if your phone supports fast charging, you could track it all the way to 3.5 if it will let it. I would not recommend the latter though.
     
    • Informative x 1
  9. David99

    David99 Active Member

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    I measured it once and it was only 0.5 Amp. They might have updated the USB ports since I got mine in 2014.
     
  10. deonb

    deonb Active Member

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    Interesting. How do you measure the current proffered on a USB port?
     
  11. jomo25

    jomo25 P4398

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    It was upgraded in a firmware release I think last year. I recall it is (usually) the one closer to the driver side that is 2.1a and the other is 1.0a.
     
  12. supratachophobia

    supratachophobia Active Member

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    I will go test this now that several have suggested the ports might be different.
     
  13. grichard

    grichard Member De-Luxe

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    Somebody with actual knowledge may weigh in, but I've never heard of the cars having the necessary equipment for the 12V system to add energy to the high-voltage battery. (Increasing DC voltage is necessarily energy-inefficient, anyway.) So I doubt you could add range this way, even in theory.

    Might--in theory--help a low 12V battery, though.
     
  14. grichard

    grichard Member De-Luxe

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    Actually, probably not even that, since the system has to step from 12V to 5V for the USB...
     
  15. f-stop

    f-stop Member

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    you could use a pocket USB multimeter, something like this one and see if an iPad draws more than 500mA
     
  16. msnow

    msnow Active Member

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    I thought @supratachophobia went to test this.
     
  17. supratachophobia

    supratachophobia Active Member

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    Sorry, car caught on fire. Just kidding. I did go test using a Nexus 5x equipped with USB 3.0 fast charging and a micro USB cable with a usb3.0 to micro adapter. Both ports registered 950mah max. I'm going to try with a straight up usb3.0 cable, no adapter.
     
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  18. supratachophobia

    supratachophobia Active Member

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    Ok, back again. This is by no means definitive, but it is at least repeatable in my testing environment. So I used an actual USB 3.0 cable with the two built-in USB ports as well as my PNY 12v 2.1amp flush mount adapter. Basically, the phone and the cable should be good to upwards around 3 amps so as not to be the bottleneck here. But the results are as follows:

    USB driver side: 1.5amps on the nose, repeatedly
    USB passenger side: 1.5amps on the nose repeatedly
    PNY adapter (rated for 2.1amp output @ 5v): 1.95amps on the nose, repeatedly

    So, conclusions. The onboard USB ports are limited to 1500ma, possibly 1600ma (see the following discrepancy). I can't explain the difference between the PNY's rated 2100ma and the detected 1950ma. Perhaps PNY is lying or perhaps there are losses in the charging path.

    The test setup was run with an Android software called "Ampre". If I get a chance, I may see what my Nexus 5 and Nexus 7 (micro-USB, no fast charging) does in the same tests.

    I'm running 2.24.102 currently.
     
    • Informative x 3
  19. msnow

    msnow Active Member

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    Very informative, thank you for doing this!
     
  20. BertL

    BertL Active Member

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    Thx. ...and the build or delivery date of your MS is what? (as there are old posts, combined with your data point, leading perhaps to the supposition that things may have changed with USB over time, just as other things have...)
     

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