TMC is an independent, primarily volunteer organization that relies on ad revenue to cover its operating costs. Please consider whitelisting TMC on your ad blocker and becoming a Supporting Member. For more info: Support TMC

Model 3 Tripping 50amp breaker @ 40amp charging

Discussion in 'Model 3' started by MikeQ, Aug 24, 2018.

  1. MikeQ

    MikeQ Member

    Joined:
    Jun 26, 2017
    Messages:
    235
    Location:
    Central Florida
    My Model 3 keeps tripping the 50amp breaker my HPWC is connected to. The HPWC is the only thing on the circuit. I'm charging at 40amp.

    What's interesting is I also have a Model X which also charges at 40amps. It never trips the breaker.

    Anyone seeing something similar with one model tripping and another not?
     
  2. gurtburns

    gurtburns Member

    Joined:
    Jun 21, 2018
    Messages:
    49
    Location:
    15071
    Is the HPWC set for a 50amp circuit breaker?
    If the 3 is failing to limit the current (Software bug or something) then a sensitive breaker can trip early (48Amps)

    Otherwise it sounds like circuit short. Not sure why it would short on the 3 and not the X.
     
  3. SageBrush

    SageBrush 2018: Drain the Sewer

    Joined:
    May 7, 2015
    Messages:
    6,367
    Location:
    Colorado
    Huh.
    My guess would be a crappy breaker that trips much closer to 40 than 50 Amps.
    I would either replace the breaker or dial down the Model 3 a couple of Amps. Try charging at 37 A
     
    • Like x 1
  4. adaptabl

    adaptabl Member

    Joined:
    Mar 13, 2018
    Messages:
    586
    Location:
    Canada
    What brand is your panel and breaker?
     
  5. MikeQ

    MikeQ Member

    Joined:
    Jun 26, 2017
    Messages:
    235
    Location:
    Central Florida
    The HPWC is set to 50amps. The HPWC seems to be getting hot on the Model 3 too and not on the X.

    I don't think it's the breaker. I think it's the car. We set it down to 35amps after the second trip. So far it hasn't tripped again. Seems like the Model 3 is pulling more power than X at the same amperage setting.
     
  6. nwdiver

    nwdiver Active Member

    Joined:
    Feb 17, 2013
    Messages:
    4,217
    Location:
    United States
    That's weird. Try noting the voltage when the X is charging @40A... then slowly increase the amps on the 3 and take note at what amp level the 3 pulls down voltage to the same level the X was at...
     
    • Helpful x 3
  7. Lloyd

    Lloyd Well-Known Member

    Joined:
    Jan 12, 2011
    Messages:
    5,785
    Location:
    San Luis Obispo, CA
    Open the HPWC and check the connections. It should not be getting too warm.
     
    • Like x 2
  8. xpitxbullx

    xpitxbullx Member

    Joined:
    Jun 15, 2018
    Messages:
    231
    Location:
    Las Vegas
    I had a 60 amp setup installed so I never had this issue.
     
  9. brkaus

    brkaus Active Member

    Joined:
    Jul 8, 2014
    Messages:
    4,362
    Location:
    Austin, TX
    Any chance you have an amp meter you could put on the wire?

    I would replace the breaker. My first install w/ a new breaker was constantly tripping at 40A. I set it down to 38A and it worked ok (but breaker did get warm). Replacement breaker didn't get warm at all charging at 40A
     
    • Like x 1
  10. ℬête Noire

    ℬête Noire Active Member

    Joined:
    Jan 30, 2018
    Messages:
    2,559
    Location:
    TX
    #10 ℬête Noire, Aug 25, 2018
    Last edited: Aug 25, 2018
    Is your breaker box in an area that gets hot [in the summer]? House circuit breakers trip based on heat, so a breaker whose trip point is in the lower margins of it's design and is operating near 80% the nominal current capacity for extended periods of time can be pushed over the top by direct sunlight or something. Remember that a 50A breaker is supposed to trip if the current goes over 40A for a couple minutes (I forget the exact target spec), so drawing 40A continuous is right at the edge even though a lot of breakers won't trip until the current goes somewhat higher (the +/- manufacturing tolerances on these physical breakers is typically pretty bad).

    As for the difference from the Model X, maybe the Model 3 is more aggressive about taking it "to the line" and relying on the A/C to keep the battery and power circuits operating safely? Maybe the Model 3 is able to draw that power continuous for longer periods of time, compared to the Model X?
     
    • Like x 2
  11. gaswalla

    gaswalla P4201/85/airsusp/pano/19i

    Joined:
    Sep 23, 2012
    Messages:
    2,023
    Location:
    San Diego
    If your other Tesla charges just fine on the HPWC, then it is a problem isolated to the Model 3. There have been a number of cars - early builds I believe - that have faulty Power Conversion Systems that would cause something like this. I speak from experience and info from the service center. Ask for a remote diagnostics - that may isolate the issue.
     
    • Informative x 2
    • Helpful x 1
  12. voip-ninja

    voip-ninja Give me some sugar baby

    Joined:
    Mar 15, 2012
    Messages:
    2,723
    Location:
    Colorado
    The continuous load spec is I believe 3 hours.
     
  13. wws

    wws Member

    Joined:
    Aug 11, 2014
    Messages:
    341
    Location:
    California
    Funny you mention it - because this just started happening to me. A couple of times now, the breaker trips after maybe 30 minutes or so. My subpanel is about four years old - a Square D Homeline with 50 amp HOM double pole breaker protecting a NEMA 14-50. I use a JESLA which is a Gen 1 UMC with a J1772 grafted on to it. Been using it daily with our Volt for several years without problem.

    I am dialing down the current to 36 amps. Voltage is low 240s.

    Considering redoing the setup to a 60 amp connection with wall charger. Then buying a Tesla-J1772 "JDapter" so I can charge the Volt with it.
     
  14. nwdiver

    nwdiver Active Member

    Joined:
    Feb 17, 2013
    Messages:
    4,217
    Location:
    United States
    It sounds like the car is misreading the pilot signal from the EVSE or is misreading its own current signal. Anyone have a clamp on amp meter or something to see if the current being pulled by the car matches how much current the car thinks it's pulling?
     
    • Like x 1
  15. ℬête Noire

    ℬête Noire Active Member

    Joined:
    Jan 30, 2018
    Messages:
    2,559
    Location:
    TX
    That's still more than the Volt would have ever drawn. Volts/Bolts are 32A nominal draw (usually a bit below that in practice).
     
  16. nwdiver

    nwdiver Active Member

    Joined:
    Feb 17, 2013
    Messages:
    4,217
    Location:
    United States
    Only the 2019 Volt is 32A. All others are 16A.
     
    • Informative x 1
  17. wws

    wws Member

    Joined:
    Aug 11, 2014
    Messages:
    341
    Location:
    California
    Well the car reads the pilot signal as 40 amps. Shows on the display that way. So I have started dialing it down a few. Perhaps it is drawing a few more amps than it says it is?

    And yes, the Volt only draws 16 amps. So way less than what the circuit is rated for.
     
  18. SageBrush

    SageBrush 2018: Drain the Sewer

    Joined:
    May 7, 2015
    Messages:
    6,367
    Location:
    Colorado
    Per the EPA, the car pulls 87 kWh from the meter to charge from empty to full.
    40 Amps * 240V = 9.6 kW, so each hour of charging should increase the battery percentage ~ 11% at SoC levels that do not constrain the charging rate.
     
  19. tomc603

    tomc603 Member

    Joined:
    Jul 28, 2017
    Messages:
    209
    Location:
    NH, US
    There's a couple things you should look into here. First, don't trust what the screen tells you for power, since you don't necessarily know what data is being measured, or to what accuracy the value is measured. We know for sure the car doesn't show values below 1kW and that it doesn't display fractional values, but that's about all we know.

    First, if you're not comfortable with these steps, or know what they mean, pay a professional. You can kill yourself instantly, so don't risk it.

    Get a voltmeter and ammeter. You can get a combined device, and non-contact versions exist, though for voltage testing you need to use probes to do it right.

    • Test the voltage between the two hot legs. The value should be within 3% of 240v.
    • Test the voltage between each hot leg and ground. The values should be within 3% of 120v.
    • The maximum voltage drop should not be more than 5%. If it is, it violates the NEC, and it could be a clear cause for your problem.

    • Clamp the ammeter around one of the hot legs before the HPWC. Plug the charger into the car and observe the measured amperage.
    • Clamp the ammeter around the other hot leg, and repeat the measurement.
    • These values should not measure over 40A.

    • Measure the temperature of each leg with a no-contact IR thermometer after the vehicle has been charging for a while.
    • If the breaker trips, measure the temperature of the breaker in the panel with a non-contact IR thermometer, as well as the feeder wires.

    If your voltage drop is over 3% or the feeder/branch wire is getting hot, it's very likely that the circuit was not installed with the proper wire gauge somewhere between the panel and the HPWC. This can cause a fire. Wire is rated for temperature ranges, and if yours is getting hot it can melt the insulation off, short out on the conduit or inside your walls, and someone could get hurt or die. Nobody should be messing with an electrical circuit that doesn't behave properly.

    If the voltages measure properly, the ammeter doesn't read above 40A, and the hot legs in the circuit aren't getting temperature hot, then it's just as likely that your breaker is garbage and too sensitive. The fact that your other Tesla doesn't cause this issue can be attributed to a million different variables that we simply don't know without detailed measurements being taken. Either way, if there's something wrong with the circuit, please stop tempting fate. People lose property and die due to electrical fires, and it's not worth the risk. Get an electrician to look at the circuit, tell them what you're trying to do, and let them make a recommendation to you.
     
    • Helpful x 3
    • Informative x 1
    • Like x 1
  20. nwdiver

    nwdiver Active Member

    Joined:
    Feb 17, 2013
    Messages:
    4,217
    Location:
    United States
    #20 nwdiver, Aug 25, 2018
    Last edited: Aug 25, 2018
    Sure.... but the charger is able to pull 48A. I'm not an electrical engineer but I would think it might be possible something isn't calibrated correctly and the car is either misinterpreting a 40A pilot signal as >40A or the car thinks it's pulling 40A when it's really pulling >40A.

    The car SHOULD detect and prevent this. I know my car has slowed / stopped charging because of a voltage drop... I hope this becomes a NFPA requirement for EVs.
     

Share This Page

  • About Us

    Formed in 2006, Tesla Motors Club (TMC) was the first independent online Tesla community. Today it remains the largest and most dynamic community of Tesla enthusiasts. Learn more.
  • Do you value your experience at TMC? Consider becoming a Supporting Member of Tesla Motors Club. As a thank you for your contribution, you'll get nearly no ads in the Community and Groups sections. Additional perks are available depending on the level of contribution. Please visit the Account Upgrades page for more details.


    SUPPORT TMC