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50 amp circuit charging rate help

Discussion in 'Model 3: Battery & Charging' started by BlueWRXPride, Jun 30, 2018.

  1. BlueWRXPride

    BlueWRXPride Member

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    I installed a 240v line using 6 gauge wire and a 50 amp breaker. When I plug in the mobile charger using the NEMA 14-50 adapter, the car says it is charging at 32 amps and gaining 13 mi/hr. I though I'd be getting a much higher charging rate, is something wrong?
     
  2. P85_DA

    P85_DA Supporting Member

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    that is what the new Gen2 UMC is rated for .. if u want faster get HPWC
     
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  3. PJFW8

    PJFW8 Red Menace may hurt me

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    Keep in mind that 6 gauge “romex” wire will only support 40amps (50 amp breaker) even if hard wired. The same size wire pulled in conduit will support 48 if hard wired to a HPWC.You can get higher temperature rated Romex style wire as well.
     
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  4. TexasEV

    TexasEV Well-Known Member

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    32A is correct for the Gen 2 UMC with 14-50 adapter as noted, but 13 miles/hr is not. At 240V and 32A a Model 3 adds about 30 miles/hr. It takes a minute or two for the charging rate display to increase— if you keep watching it I bet it will go up to 30 miles/hr and stay there.
     
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  5. BlueWRXPride

    BlueWRXPride Member

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    I wish, but it's been at 13mi/hr for at least an hour.
     
  6. gaswalla

    gaswalla P4201/85/airsusp/pano/19i

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    Please post a screenshot... 32 amps is ok. Shouldn't be 13 mph though
     
  7. TexasEV

    TexasEV Well-Known Member

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    Is it possible you’re only charging at 120V? As posted above a screenshot of the charging screen will help.
     
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  8. BlueWRXPride

    BlueWRXPride Member

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    You're right, it's only charging at 120V (113V to be precise). Think it's wired up wrong?
     

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  9. KJD

    KJD Supporting Member

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    Can you post a picture of the wires going into the breaker in the panel.
     
  10. BlueWRXPride

    BlueWRXPride Member

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    I can, but it'll take me a bit to get home to do that. But it doesn't seem like there's much to mess up, black and red to the double breaker, green and white to the neutral/ground bar.
     
  11. BlueWRXPride

    BlueWRXPride Member

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    Would it be charging slower because the battery is somewhat full?
     
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  12. KJD

    KJD Supporting Member

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    Sounds like you got it right, but a picture would help verify that.
     
  13. BlueWRXPride

    BlueWRXPride Member

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    The mistake was at the 14-50 plug, hot and ground were swapped. I fixed it and readings are as expected now.
     
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  14. KJD

    KJD Supporting Member

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    Glad to hear that you figured it out. Enjoy that new car. :)
     
  15. iluvmacs

    iluvmacs Member

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    Wow, that's downright dangerous. Applying 120VAC to the ground pin input to the UMC may have damaged it as well. I'm surprised it even ran at all.
     
  16. tivoboy

    tivoboy Member

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    Volts should stay the same, amps should drop in half when it gets full, no?
     
  17. TexasEV

    TexasEV Well-Known Member

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    Close. Volts stays the same and amps gradually drops. But anyway this car wasn’t near full. When charging from an outlet or HPWC the rate doesn’t start declining until state of charge is well over 90%. It’s not like supercharging.
     
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  18. eprosenx

    eprosenx Member

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    This is totally correct except a caveat to the last sentence. Yes, you can get NM wire (Romex) that has higher insulation ratings than 60c, (it is typically 75c or 90c rated I think), but per NEC you are not allowed to use it at any listing above the 60c ampacity. (you can however use the higher listings to do temperature deratings and such like when running in attics - so that is useful)

    What is stated here is correct as long as you are working in the main service panel which is the only place neutral and ground are tied together. If you are in a subpanel then neutral and ground are on separate busses and neutral is isolated from ground. So you need to hook the wires to the correct places (everything would work fine if it was wrong, but in some situations you could create a hazard - so make sure to get this right!).

    This is a good callout, battery charging will slow down as it gets close to 100%. But it was not the issue in this case.

    Wow, that is not good. Glad you fixed it! Since that was wrong, did you make sure that neutral and ground are hooked up to the correct ports? You would not be able to see this being "wrong" with a multimeter and the UMC would not have an issue with it, but you could be running current on a grounding wire which may not be of sufficient ampacity (well, this would only apply if you actually *used* the neutral which the UMC does not, but you get the idea - though having your ground wire connected to the neutral and not ground in some contrived situations could also be dangerous).

    I am wondering if this is what actually happened. My guess is that one hot and neutral were what was swapped. If ground and a hot were swapped then the UMC would have seen 120v from one hot to "ground", and 240v from the other hot to "ground" during its test and only 120v from "hot to hot". It seems like the UMC should be smart enough to not allow the car to charge in that mode. If neutral and one hot were swapped the UMC would see 0v from one hot to ground, 120v from the other hot to ground, and 120v from "hot to hot". This is exactly what the UMC sees when charging from 120v sources so it is just fine with that.

    I highly doubt any damage would happen since the UMC is rated for 120/208/240v operation (actually, I suspect it is rated for 100-240v operation would be my guess - but I don't have one yet to check).

    The danger of wiring a hot to the ground pin I could see being that the ground on the UMC may be connected to the chassis of the car when charging (I am not sure). That would make the potential from the car to ground be 120v! Really not cool!!! (actually, can anyone confirm if ground on the UMC is tied to the vehicle chassis ground?)
     
  19. BlueWRXPride

    BlueWRXPride Member

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    Thanks eprosenx, lots of good info there! The wire I had run is 6 AWG THHN run through conduit. Does that mean it should be able to handle 48 amps or is 32 still the max?
     
  20. eprosenx

    eprosenx Member

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    #6 AWG THHN copper wire run in conduit is good for 65 amps at the 75c rating (so the breaker and the thing on the end of the circuit have to be rated to 75c terminals also).

    So you can use it on a NEMA 14-50 receptacle with a 50 amp breaker no problem. You are not allowed to use a breaker that is larger than the receptacle it is connected to.

    If you took that same wire and hooked it to a Wall Connector you could replace the breaker with a 60a one and charge at up to 48 amps on the car (cars are considered continuous load and so you have to keep 25% extra overhead on the wire and breaker for an added margin safety).

    Note that the UMC Gen 2 is only good for 32 amps regardless of the size of the circuit it is connected to. The Wall Connector can do up to 80 amps on a 100a breaker but the Model 3 Long Range will only use 48 amps, the short range only 32 max.
     

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