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Question for the electricians here....why is car only pulling 202v?

Discussion in 'Model S: Battery & Charging' started by pete8314, Jul 8, 2013.

  1. pete8314

    pete8314 Vendor

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    As you can see in the screenshot below, when I plug my car in at the office, it only pulls 202v @ 40A, rather than the ~240v it pulls at other locations, including home (UMC, single charger).

    Now, I should say that I'm grateful my office installed the 14-50 for me, but, to be fair, I think our on-site electrician isn't exceptionally experienced. I did ask him why it was only pulling 202v, but he had no idea.

    So do any of the electricians on here have any pointers I could offer him? Thanks....

    photo.PNG
     
  2. dsm363

    dsm363 Roadster + Sig Model S

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    This is just a guess but don't a lot of commercial sites have three phase power meaning you get around 208V?
     
  3. pete8314

    pete8314 Vendor

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    I did ask that, and he said it was on a single-phase circuit...the same breaker box (but not the same breaker) that he pulled the 110 from for the Volt charging outlet.
     
  4. AmpedRealtor

    AmpedRealtor Active Member

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    Model S uses the current that is provided, so your utility company or electrical panel is only supplying 202v. The car can't change the voltage it's given.
     
  5. adric22

    adric22 Member

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    Amps are pulled, voltage is supplied. The car doesn't get a choice over what voltage is supplied. It does have a choice how many amps it wants to pull, though. I would also guess something is feeding from a 3-phase circuit.
     
  6. deonb

    deonb Active Member

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    Did you happen to notice how many volts it starts out at (when it's still at 0 A)?

    It could be (dangerously) undersized cabling.
     
  7. TurboFroggy

    TurboFroggy Member

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    Commercial power is typically 208V so that plus a few volts of voltage drop for a long wire run can equal as little as 199 volts. At home the standard is 120V X 2 = 240V.
     
  8. pete8314

    pete8314 Vendor

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    I'm 90% certain it starts out at 240v, but I'll check. I did have a UMC melt on the outlet (now both replaced), but that was assumed to be a bad UMC....nothing gets particularly hot on the new one.

    - - - Updated - - -

    Wire run is about 100ft, give or take 20ft.
     
  9. pgiralt

    pgiralt Active Member

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    As others have mentioned, most commercial power is 3-phase so the voltage across two phases is 208V, not 240V due to the phase alignment (120 degrees out of phase as opposed to 180 degrees out of phase). The wire gauge could be leading to some resistance further reducing the voltage down to 202V.
     
  10. mitch672

    mitch672 Active Member

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    You have 3 phase commercial power in your building. Set the Model S to 5A, I bet it's showing around 207-208V, when you load it down with 40A, your getting some voltage drop in the wiring, and possibly from the utility transformer as well. Your service is known as "120/208 WYE" (120V between neutral and any leg, 208V between any 2 phases)
     
  11. deonb

    deonb Active Member

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    Dropping 38 Volts over 100ft at 40 Amps is an indication that your 240V outlet has 16 Gauge wiring behind it... I'm going to use the anthropic principle and say that since you're alive to tell this story, that is NOT actually what is happening :).

    Double check the initial voltage. If it really is 240 dropping to 202, unplug everything - you have a wiring fault. (I suspect it starts at 208 though, and have just a slight voltage drop.)


    PS: It's not the UMC that will heat up if it's undersized, it's the wire run behind the outlet. Not sure if you have access to that.
     
  12. markb1

    markb1 Active Member

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    I was under the impression that the Model S will actually refuse to charge is it sees a large voltage drop, because it assumes there's an extension cord in use. Though I don't think a 240 to 202 voltage drop is necessarily dangerous, if it's happening over a very long length of wire.
     
  13. RandyS

    RandyS Fan of Elon

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    It's not dropping 38 volts...As mentioned above, commercial power is typically delivered at 120/208v, and there is a tiny bit of voltage drop from that at 40 amps...Looks normal to me....
     
  14. pete8314

    pete8314 Vendor

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    I just restarted the charging remotely, and it did start at 206v. Will try the same when I'm by the car later.

    Not sure if this is at all relevant, but when I just checked the charging, the voltage was up to 205v, and the amps down to 32A:

    photo1.PNG
     
  15. deonb

    deonb Active Member

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    I'm basing that purely on his quote:



    So until he confirms otherwise, it's dropping 38 volts :). I agree that the far more likely scenario is that it's not starting at 240v, but since he is 90% certain, it wouldn't hurt to double check.


    [EDIT: My reply passed his in the air - confirmed, it wasn't starting at 240v.]
     
  16. markb1

    markb1 Active Member

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    What we really need to know is the voltage when it's at nearly 0 amps.
     
  17. bluetinc

    bluetinc Member

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    Hey Pete,

    I'm fairly sure that as others have said the building is supplied with 3 phase power BUT if the voltage shown before you draw any current is really 240V or so, don't charge until the cause is isolated (bad connection in the line, undersized wire, etc.). That would mean a 38V drop due to load which is way out of acceptable and should be considered dangerous (basically means there is a 1.5 KW heater somewhere it shouldn't be and will melt wires and start a fire).

    Peter

     
  18. jerry33

    jerry33 S85 - VIN:P05130 - 3/2/13

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    The quote says it all: At the office Pete is getting 208V because it's 3 phase commercial power and in other locations he's getting 240V single phase.
     

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