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Possible Bug found in 2017.34 2448cfc

Discussion in 'Model S' started by Bumper, Sep 8, 2017.

  1. Bumper

    Bumper Member

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    I normally charge with my UMC cable and the NEMA 5-20 adapter. I have always pulled 16 AMPS from the 5-20 outlet. Last night I upgraded the above firmware and now I only charge at 12 AMPS. I tried adjusting on the charger screen but it only allows 12 AMPS. Anyone else use this type of plug seeing the same?

    I tried to post as a bug on Tesla page but keep getting web site errors....
     
  2. boaterva

    boaterva Supporting Member

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    Tried rebooting just to be sure? That is weird...
     
  3. MorrisonHiker

    MorrisonHiker S 90D 2017.34 2448cfc

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    I'll try the 5-20 adapter when I get home and see if it is still working for us.
     
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  4. Bumper

    Bumper Member

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    I ran out to the car and rebooted both screens. I also unplugged both ends of UMC and plugged back in. Still only getting 12 amps.
     
  5. MorrisonHiker

    MorrisonHiker S 90D 2017.34 2448cfc

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    #5 MorrisonHiker, Sep 8, 2017
    Last edited: Sep 8, 2017
    Looks like it might be a problem with something on your end. I'm still getting 16 amps with my 5-20 adapter.
    20170908_153451.jpg
    I took this right after plugging in so it is only showing 3 mph. If I let it ramp up for a few more minutes, I think I'd get over 5 mph with this adapter.
     
  6. MP3Mike

    MP3Mike Active Member

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    Maybe try using the 5-15 adapter and then switching back to the 5-20 to see if that gets it to update.
     
  7. murphyS90D

    murphyS90D Member

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    @MorrisonHiker
    Why is your voltage down to 110 volts? That 10 volt drop from 120 volts indicates a circuit that is not properly wired for 20 amps. A 20 amp circuit must be wired with a minimum of 12 gauge wire and if it is an overly long run it should be 10 gauge wire. Also check that the receptacle was wired using the screws. The push in holes are only suitable for table lamps.

    I charge at my brother's house using a 5-20 adapter and a 50 foot 10 gauge extension cord
    and always get 5 mph at 120 volts.

    Yes I know that Tesla says not to use an extension cord. That is because the extension cords that most people have lying around are made with 16 gauge wire which is totally wrong and dangerous for this application.
     
  8. conman

    conman Member

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    Could be coincidence and nothing to do with the software upgrade. If the internal charger detects instability or poor current supply in the line it will automatically drop the setting itself.
     
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  9. MorrisonHiker

    MorrisonHiker S 90D 2017.34 2448cfc

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    I have a very long wiring run. It's about 100 feet from the main panel to the garage subpanel and over 50 feet from the subpanel to that outlet. I'm sure it has the correct gauge wiring since it was just put in two years ago. When they were installing it, I asked why it was yellow vs white and they said it was a higher gauge. I'll have to check and confirm it is connected with screws.
     
  10. tls

    tls Member

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    Yellow NM cable from the major brands (e.g. Romex) is #12. White NM cable is #14 and, because of the code rule requiring that small wire sizes be increased by 1, it wouldn't be permissible to connect a known 20A load using #14.

    An actual 20A outlet will typically not have the spring-loaded "backwire" or "stab" terminals common to 15A devices. There may be holes on the back but they are clamped down by turning a screw. These are fine. I agree that spring-loaded backstab terminals are to be avoided unless working in a very tight existing box where the saving in space from wiring through the device (using both terminals) is necessary.

    Anyway, your electrician didn't upsize the wire for the long run, you've got the wire size required by code. Do you know what your starting voltage is before you begin to charge? You may have to be pretty quick to see it with only 12A of ramp-up but it'll be displayed on the instrument cluster at the very beginning of the charge cycle.

    I don't know if the threshold used at low amperages differs, but the car will usually tolerate about a 10% voltage drop before limiting current. That suggests you would have had to drop to that 110V you're seeing from an initial (no load) voltage somewhere above 120 -- is that the case?

    Do you have another large load on the subpanel (say, a washer or dryer) which might have kicked in at some point just as the car was starting to charge, making it think the wiring at this location was unreliable? If so, restarting the car is likely to help.
     
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  11. Bumper

    Bumper Member

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    In my case, The voltage shows 117v. I am in parking garage with many NEMA 5-20 plugs. These are commercial boxes with conduit strapped to the concrete walls. I don't know what wire is inside, but it certainly has not changed in the past few days.

    I have 4 different outlets that I have used in the past week and drawn 16amp continuous. Now each only provides 12amp. This is day 2 so I don't think some other load has kicked in to affect 4 plugs on 2 different floors.
     
  12. appleguru

    appleguru Member

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    Just tested on my 75D with the same fw version. I am still able to pull 16A.

    Try the reset button on your UMC? Also, check the resistance between the pilot pins (the small pins on the back of your nema adapter).

    My 12A adapter shows 140k Ohms
    My 16A adapter shows 75k Ohms
    My 40A adapter shows 9.1k Ohms
     

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  13. Bumper

    Bumper Member

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    @appleguru,
    I get pretty much the same resistance measurements as you do. (See attached)

    After putting the 5-20 back on, and hitting the reset button, I am once again back up to 16amps. Not sure which part did the trick but I thank you for your help!

    I added one more picture because this car is just as much a toy as a tool!


    IMG_2347.JPG IMG_2348.JPG IMG_2349.jpg IMG_2350.jpg IMG_2351.JPG
     
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  14. caltrader

    caltrader Supporting Member

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    Only getting 12A here...
     
  15. MorrisonHiker

    MorrisonHiker S 90D 2017.34 2448cfc

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    @tls Just an FYI, but I'm not the OP. I have no problem charging in my garage despite the long wiring run. I normally use the 14-50 outlets and only plugged into the 5-20 to confirm it can still draw 16 amps. Thanks for the info. I never use any 20 amp devices on those outlets so maybe I'll just convert them to 5-15.
     
  16. tpham07

    tpham07 Member

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    call tesla support and see whats up
     

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