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Charging with single 10kW charger at more than 40amps

Discussion in 'Model S: Battery & Charging' started by richkae, Oct 11, 2012.

  1. richkae

    richkae VIN587

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    Some of the 30amp J1772 chargers I have seen are not 7.2 kW or even 6.6kW, they are actually only 6.0kW because instead of being 30amps @ 240volts, they are hooked up to 208 volts.
    However there is so much voltage drop to the unit that they really only deliver 200 or 201 volts - thus 6.0kW.

    If you plugged a Model S with the single 10kW charger into a real 20kW HPC ( 240 volts 80 amps max ) - then you can draw 9.6kW by pulling 40 amps @ 240 volts.
    However if it is a 208 volt unit with a lot of voltage drop - then 40amps @ 200volts is only 8.0kW.

    Thus my question - can you dial the amps up to 48 amps so that you have 48amps @ 200 volts which is 9.6kW?
    Even if it was a full 208volts, 48amps would be 9.98kW just barely under 10kW.
     
  2. qwk

    qwk Model S P2681

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    I'm sure it's possible, but not with any firmware that Tesla would release.
     
  3. mitch672

    mitch672 Active Member

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    Not a good idea. There's a reason why the maximum amperage is limited to %80 of the circuit ampacity, it's due to the continuous nature of EV charging, and circuit breaker heating. I think you would discover a good number of circuit breakers would trip under your proposal. Can it be done? Sure, you would have to generate your own J-1772 pilot signal to tell the Model S you had more capacity available than you do.. You would have to advertise 60A available to the Model S to be able to set the charging current to 48A.
     
  4. richkae

    richkae VIN587

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    I think you misread my post. I'm saying you plug the car in to an 80amp capable HPC that is only pushing 200 volts. Its generating an 80amp pilot signal.
    But the car can only handle 10kW.
     
  5. mitch672

    mitch672 Active Member

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    Ok, still a 10KW single charger is not going to be allowed to draw more than 40A, even if offered an 80A capacity EVSE.
    The WHPC is really designed for residential installation, the vast majority of homes run 240V split phase, not 208V 3 phase.
    It's hard to imagine Tesla will somehow calculate actual measured voltage into the chargers current draw algorithm.
     
  6. richkae

    richkae VIN587

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    Yeah it is designed for residential installation, but it is really a waste to do so.
    I now have two Teslas in my garage and they charge on Nema 14-50s, I don't intend to ever put an HPC in my garage.

    Small groups of owners getting together and putting in an HPC along some route they want to drive is the best way for us to extend our range to places that the Superchargers won't go any time soon.
     
  7. GSP

    GSP Member

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    The Model S charger most likely can handle 40A max, since most power electronic devices are designed to a max current. So if you are using public charging stations at 208v (or less), the charging mph will be lower than a 240v station. This would be an advantage of the Twin Charger option. With an 80A rating, you could use the full ampacity available at public stations.

    GSP
     
  8. Kevin Sharpe

    Kevin Sharpe Active Member

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    Absolutely! :biggrin:
     

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