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Mobile connector at 230v, 28mi/hr? voltage drop or normal?

Discussion in 'Model 3: Battery & Charging' started by ezevphl, Aug 16, 2018.

  1. ezevphl

    ezevphl Member

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    So we've had the car for over a month, but used a 110 or other chargers until now.

    My electrician just installed the 14-50 outlet and the car seems to be charging normally.

    The app is showing 28 miles per hour at 230v at 32amp.

    So it appears about normal, but not the 'ideal' 30 miles per hour?

    We have a pretty long cable run. Maybe a bit over 100 ft from the main panel to the sidewalk charger.

    Am I looking at a voltage drop or is this just normal and could be due to the car battery being over 70% at this point?
     
  2. Lloyd

    Lloyd Well-Known Member

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    Depends on what you started with.
     
  3. MorrisonHiker

    MorrisonHiker S 90D 2018.32.4

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    I think that's less than a 5% drop so I wouldn't be concerned about that 1-2 mph that you aren't getting. We have a long cable run as well and have been seeing some voltage drops (and then the amps dropping when charging). We believed it was due to the long run but had Tesla out to investigate yesterday. They found we're getting 247 volts right where the lines connect to the electric meter. If we turn start charging, turn on the oven, etc., we saw it drop to less than 220 volts in the garage. In our situation, it looks like a transformer issue and has nothing to do with the long cable run. Tesla is checking our charging logs and will be providing them to our utility company. Hopefully they'll see that our usage (along with our neighbor's pool pump, etc.) warrant a newer transformer.
     
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  4. Cosmacelf

    Cosmacelf Well-Known Member

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    230v under load isn’t unusual. Also, I do believe the MPH charging number is still a session average number, not instantaneous, unlike all the other numbers? If I’m correct, that MPH number would be skewed smaller at the beginning of a charge due to the ramp up time (it ramps up from 0 amps). Check to see what the MPH number is after 10 minutes of charging...
     
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  5. tes-s

    tes-s Member

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    In Philadelphia, your service should be 120v/240v. I doubt you have 110v or 220v anywhere.

    When you are charging, measure the voltage at your panel and see what you get. It should be close to 240v. If it is below 235v, I suggest calling your power company and tell them.

    If there is a large voltage drop between the panel and what your car is displaying there could be a problem with the breaker, wiring, connections, or mobile connector.

    I typically see 240v before my car starts charging. When charging at 80a, it dips to 238v.
     
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  6. TexasEV

    TexasEV Well-Known Member

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    Perfectly normal. You’re not getting 29 or 30 mph because you’re not charging at 240V. Nothing to do with your battery SOC. With AC charging the rate doesn’t start tapering until well past 90%.
     
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  7. ezevphl

    ezevphl Member

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    That was after about 10 min of charging.
     
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  8. ezevphl

    ezevphl Member

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    120 service, it was charging at about 110.
    I guess it could be the same reason that its 230 and not 240.
     
  9. Rockster

    Rockster Active Member

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    Do you happen to know what gauge of wire the electrician used for the 100' run?
     
  10. ezevphl

    ezevphl Member

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    I believe 6 gauge. It was originally run 2.5 years ago for a phev with a 15 amp breaker and regular outlet at the end.

    A different electrician just swapped the outlet and breaker today.
     
  11. eprosenx

    eprosenx Member

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    So while 230v is a little bit low, it is just barely within 5% of nominal which is 240v. 5% low is 229v.

    You should expect the utility to fluctuate up and down throughout the day within a range, and then you further have significant fixed losses for your long run to the car.

    If you take the ideal 30 miles per hour of charge and subtract 5% then that is about 28 miles per hour.

    It would be interesting to check your voltage at the EVSE prior to charging, and then after commencing charging. The same goes for at your main service entrance (electrical panel).

    That is awesome that Tesla will help you provide logs! Yes, this absolutely sounds like a power company problem. Probably just an undersized transformer, but could also be undersized conductor wires to your meter or loose / poor connections. I am curious what the result will be!

    Ah yes, at 6 gauge you are going to get some decent loss at that distance with 32 amps flowing over it. I think it is totally fine though.

    I also did not mention - might it have been taking some power to heat / cool the battery? What were temps during this test?

    So I was just noticing my utility was at 229v last night which shocked me. It normally is maybe + or - 4 volts from 240v.

    The power grid is a pretty fascinating thing. Typically they have "Online Tap Changers" on the output side of all the substation utility transformers. Throughout the day as transmission voltages fluctuate (due to loading on the overall grid) the tap changers will operate (change settings) to boost/drop the voltage on the distribution system periodically throughout the day. So if you ever look at a graph of it you will see voltage smoothly (usually) fluctuate up and down, but then it is interrupted by big jumps up and down (well, jumps of like 2-4 volts I think) as the tap changers operate.

    I would check your voltage at different times of day to see what you see over time. I doubt you need to worry too much!
     
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  12. TexasEV

    TexasEV Well-Known Member

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    Seems unusual to have had 6 gauge wire run for a 15A circuit. Better check that to be sure now that you’re pulling 32A continuously.
     
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  13. ezevphl

    ezevphl Member

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    We ran it knowing that I would get a Tesla one day. Had to run outside and under several sidewalks, so this was going to be a one time deal.
     
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  14. eprosenx

    eprosenx Member

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    Nice thinking ahead! Is it in conduit so it could be replaced some day if needed?

    I am curious: Are you using a UMC Gen 2 then to charge? How do you keep it from being stolen?

    I did want to call out that I recently discovered that 2017 NEC now requires GFCI breakers on EVSE outlets. Did your electrician install one?

    I personally am not a fan of this requirement of receptacles installed indoors, though I can see the merits for outdoor receptacles (though they are very expensive breakers still).

    The State of Oregon struck a lot of the 2017 NEC requirements for GFCI's in new parts of the code, but it would seem they missed striking the one for EVSE's. I am waiting to hear back from the Chief Inspector for the state on to whether the committee is going to go ahead and strike the requirement or otherwise modify it as it sits in the 2017 code.

    I will say that every RV park out there I think has non-GFCI 50a receptacles, so it can't be *that* dangerous, but I figured I would point it out!

    P.S. To me, this code requirement is going to push folks more in the Wall Connector direction since the GFCI breaker is then not needed. If you plan to buy a second UMC for charging (so you can keep one in the car) then the cost delta between the UMC and the Wall Connector is $200. If you have to pay an extra $100 for a GFCI breaker then you are only $100 apart. You also don't need a neutral wire for the Wall Connector (though you can accomplish the same thing with a 6-50 receptacle), and you don't have to pay for the receptacle itself. Not to mention the Wall Connector can charge your car faster with sufficient ampacity wire (your 6awg could charge a 40a for instance in any case, and even at 48a if in conduit the whole way).
     
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  15. Kermee

    Kermee It's Not Easy Being Green

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    From the UMC2 Manual:

    Note: To prevent unauthorized unplugging of the charge cable, the vehicle must be unlocked or able to recognize a key nearby before you can disconnect the charge cable.

    However, it may not prevent someone from unplugging the UMC2 from the outlet and taking whichever NEMA adapter you have plugged into the UMC2.
     
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  16. tes-s

    tes-s Member

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    You have a voltage issue. No way the load from charging on 120v would cause a voltage drop.

    Call your utility - they are delivering low voltage to your house.
     
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  17. Cosmacelf

    Cosmacelf Well-Known Member

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    Uh, no, that isn't evidence of a utility issue. It all depends how long a wiring run from the panel you have, whether the in wall wire uses 14 or 12 gauge, etc.
     
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  18. ezevphl

    ezevphl Member

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    Yes UMC Gen 2. This is the post with the old charging cable. The cover locks in place so its relatively secure.
    GFCI breakers installed today, my electrician knows his stuff, although the original job was too big for him with the drilling and conduit stuff.

    What I haven't figured out is a graceful way to lock the main UMC to the connector, especially when charging elsewhere.

    I believe the charger does get locked when no key is present, although I'm not sure if this stays if there is no power..
     

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  19. eprosenx

    eprosenx Member

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    So the UMC will be locked to the vehicle if the key is not present (even if the EVSE is unpowered I think - the car controls the locking). But this does not stop someone from stealing the 12" adapter on the end of the EVSE ($35). It also does not stop them from stealing it when you are away from home. I would not want to connect/disconnect a UMC from a 14-50 receptacle (or the 12" adapter) every single day - this would wear out those mating surfaces (and be annoying).

    If it is an issue, I would consider installing a Wall Connector. It can be more firmly affixed. It also would have saved you the $100 or so for the GFCI breaker as it would have been un-needed.
     
  20. tes-s

    tes-s Member

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    We won't know for sure until he measures the voltage at the panel when he is charging. Perhaps he has some knob and tube circuits. I've never seen my car report voltages that low from spec.
     

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