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Should I get any more than 30A on a 208VAC line?

Discussion in 'Model S: Battery & Charging' started by Barry, Apr 9, 2015.

  1. Barry

    Barry Member

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    New Tesla owner. I live in a mixed-use (commercial and residential) condo building, so the power coming in is 3 phase. Therefore, I get 208V rather than 240V at my NEMA 14-50. Using the Android app, I see that the charging current is 30A, rather than 40A (it shows 30/40 A. with a charging rate of 19 mi/hr. Is this the normal charging rate for a 208V line?
     
  2. TexasEV

    TexasEV Active Member

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    No. What happened is your car stepped down the amps by 25% as a safety measure because it detected a voltage drop. You need to have an electrician find out why. If it's a 50A breaker, your car will draw 40A unless the wire size is too small, there is a loose connection at the outlet, some other load is causing the voltage to drop, etc.
     
  3. Cottonwood

    Cottonwood Roadster#433, Model S#S37

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    That is about right as a charging rate for 30 Amps and 208 Volts. With 208 Volts and 40 Amps, you would get about 33% more power and about 25 mph charging.

    It looks like your car has gone to a 75% current because it is unhappy with your power and reduced current draw as a safety measure. FlasherZ did a good write up at Charging cuts down to 75%, Tesla says... it's my house. - Page 5. Read before and after that post for more musings on what the issue may be.

    Good Luck!
     
  4. BFCobra

    BFCobra Member

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    Can't say for sure, but I just hooked up this week a 30A/240v Dryer plug from the laundry room into the garage. That is enough current to keep my car charged, and sure is better than 3miles/hour of charge of the 12a/120v.... I recently received a 2013 P85+, so I too am new to this. My observation is that the SuperCharger in Gilroy charged at 236miles/hour of charge. The 12ish chargers at the Fremont factory, when all are occupied, charged at 140 miles/hour. Seems that the chargers share every other one, so if you stop there you can increase your charge rate by choosing wisely. I can always hit the SuperChargers if I travel either north or south. 90% of the time I have less than a 10 mile commute to work, so the dryer plug charges Tesse in about an hour. I changed our PG&E rate to an EVA, or around 9 cents/Kwh between 11:00 pm and 7:00 am. The socked it to you, at 42 cents between 2:00 and 9:00 pm, and otherwise its 22 cents. So Tesse charges at 11:30 pm, right about the time my eyes close for the night.... :)


    Your mileage, and electric rates, may vary, BFCobra
     
  5. scaesare

    scaesare Active Member

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    If your starting voltage was ~208 and it dropped appreciably[1] as the car ramped up charging, it may have reduced current as a safety precaution. Any idea what your starting voltage was compared to when the car started charging?

    [1] Or even not-so-appreciably... recent firmware has made this current-reduction a tad overly aggressive IMO.
     
  6. Barry

    Barry Member

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    #6 Barry, Apr 9, 2015
    Last edited: Apr 9, 2015
    I started the charge when I got home today with 155 miles remaining, with the car set to charge to 220 or so miles.
    The app says it was 203V at the car, due to the voltage drop along the line. It's a long run (350 ft) of 6 ga copper, which doesn't seem unreasonable.

    Is it that the car is expecting something close to 240, so it's cutting back as a precaution. I'll call Tesla and see what they say. Maybe it's cutting back as a precaution as the car is expecting 240 and not 208...
     
  7. scaesare

    scaesare Active Member

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    208 as a starting voltage shouldn't matter. That's a common commercial voltage, and the Tesla's chargers will happily accept that. It's the delta in voltage as a result of drop as the current ramps up that the car looks for.
     
  8. Barry

    Barry Member

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    Just got off the phone with Walter in Tesla's home charging dept. He took a look at the log and said everything was OK from the car's perspective.

    He said when you first plug in, the car measures the voltage under no load, then if there's an 8% voltage drop under load, it cuts back the current by 25%. In my case, due to the 350 ft run, there is enough drop at 40A that the car cut it back 25%. He suggested playing with the amperage setting and try something between 30 and 40 amps to lessen the voltage drop and prevent the automatic cut-back.

    Right now, I have it set to 35A and it is maintaining that level with an increase in charging rate to 22mi/h.
     
  9. Cosmacelf

    Cosmacelf Active Member

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    If you don't have a long commute, that charge rate should work just fine. Just be glad you can charge at all in your condo - there are lots of threads of people who can't get their condo to allow high powered charging.
     
  10. scaesare

    scaesare Active Member

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    Interesting... this is the first time I've heard a specific value stated by Tesla. I wonder if that 8% is accurate.

    I have about a 5% drop typically... starting at 245 ad dropping to about 233. For me to get throttled back I'd have to drop down to 225-226. I've never seen it under 230, and yet every so often I'll get throttled back to the 75% current reduction...
     
  11. Barry

    Barry Member

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    They had to approve it. Colo passed a law in 2013 requiring HOAs and landlords to accommodate charging requirements of EV owners, with the owner/tenant responsible for all installation costs. However, I feel they are taking advantage of me in overcharging for electricity. It's not that big a deal, but it's the point. I am appealing their assessment.

    I spoke with Walter several times prior to the installation to get details the HOA required. He's seems very knowledgeable (from my perspective as a BS in Engineering who never worked in Engineering) and I believe he runs the home charging installation dept. at Tesla, whatever that entails.
     

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