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Slow HPWC - any ideas?

Discussion in 'Model S: Battery & Charging' started by jefferson4door, Feb 10, 2017.

  1. jefferson4door

    Joined:
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    Washington
    I had a HPWC installed on a circuit breaker that doesn't get a ton of power, so they installed it at a 40 amp setting which according to both the electrician and the Tesla web site should be good for 23 miles per hour of charging. (Home charging installation)

    It's only getting half that - 12 miles per hour, consistently. When it's plugged into the car the app shows it charging at 16 amps (with 32 amps greyed out and no apparent ability to switch it on). Is this the way it's supposed to be?

    I don't have the high amperage charging option, but I didn't read the original web page to suggest the 23mph rate required that option. And the description of that option implies I should be getting way more than 12mph even on on 40 amps without the high amperage charging. ("Model S comes standard with a 48 amp onboard charger, allowing up to 34 miles of range per hour of charge with a Wall Connector. The included Mobile Connector can charge at a maximum of 40 amps, allowing up to 29 miles of range per hour.")

    So why shouldn't I be able to get the full 23 with my HPWC at 40 amps? Any ideas?

    TIA
     
  2. jelloslug

    jelloslug Active Member

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    Either the HPWC is not set up correctly or the car is decting a problem with the wiring and is limiting the current draw.
     
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  3. animorph

    animorph Member

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    Sounds like the HPWC is set for a 40A circuit breaker, allowing 32A continuous. On top of that it may be sensing a voltage drop between not charging and charging that exceeds its safety limit, so it is reducing the current. Look at voltage when not charging and then while charging.
     
  4. BerTX

    BerTX Active Member

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    Did you previously set your charge at a lower rate at that location? The car will remember the lower rate and limit to that setting for you...
     
  5. jefferson4door

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    New car, so this is the first time hooking it up to the HPWC.

    Yes - it is set up for a 40 amp circuit breaker. But shouldn't this be giving me the 23mph charge?
     
  6. Solarman004

    Solarman004 Member

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    There are 2 likely answers:
    1. Open the HPWC after shutting off the breaker, and verify the rotary dial setting against the table in the installation manual.
    2. The HPWC is properly set but is detecting a voltage drop which indicates a fault in the circuit. Stop using the HPWC until your electrician can troubleshoot the issue.
     
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  7. jefferson4door

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    HMM. That's what I was afraid of.

    The charging app is showing this: "12 mi/hr 248 V 16/32 A" (with the 16 in white and the 32 greyed out)
     
  8. nwdiver

    nwdiver Active Member

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    How much does voltage change?
     
  9. FlatSix911

    FlatSix911 918 Hybrid

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    Check the internal switch settings on your HPWC ... sounds like you are on switch position 2-16A :cool:

    upload_2017-2-10_19-40-3.png
     
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  10. animorph

    animorph Member

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    Yes, I think you should get about 23 MPH at 32A. Your app is showing only 16A, so you're getting more like 11-12 MPH. I believe the grayed out 32A indicates you are set for that maximum charge rate, which is correct for your 40A breaker. You just need to get that 16A reading up. Again, check your voltages. Most likely the car is concerned about the voltage drop it is seeing when charging. This could be a wiring problem (small feed to the house, small wires to the charger), or a bad connection anywhere along the power/charger circuit (such as the charger handle is not making good contact with the car). The car does report voltage while charging. If it is significantly below (10V?) your normal house voltage while not charging the car charger will reduce the charging current. In that case, your electrician will have to find the problem and fix it.
     
  11. animorph

    animorph Member

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    248V does not seem unreasonable, though that is at 16A.
     
  12. Solarman004

    Solarman004 Member

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    @jefferson4door , when first read your post I was thinking you were wired through a 40 amp circuit breaker. But re-reading the post I see you use the phrase "40 amp setting." Does this mean 40 amps supposedly set in the HPWC using a 50 amp breaker; or a 40 amp breaker for you to charge at 32 amps.

    When you check the rotary dial, make sure the breaker size you use (right column in the table) matches your actual breaker for the circuit.

    Also, confirm this is a dedicated circuit with no other appliances connected to it. Since a professional electrician installed it, it would be highly unlikely he/she would have shared an existing breaker with another appliance, but, stuff happens.
     
  13. jefferson4door

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    Yeah, it's a 50 amp breaker.
     
  14. brkaus

    brkaus Active Member

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    Unplug. Set the current to maximum on the charge screen (I think you can do that without plugging in). Plug in. Immediately watch the current and voltage. It should generally ramp the current up and the voltage should stay roughly the same. If the voltage drops, it will back off on the current.
     
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