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1 PW, 2 teslas. PW drains in an hour

Discussion in 'Tesla Energy' started by SD Diver, Mar 29, 2018.

  1. SD Diver

    SD Diver Member

    Joined:
    Apr 5, 2016
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    Location:
    San Diego
    Greetings,
    just got my Powerwall online after waiting since lat June. My first full charge was wiped out in < 2 hours when Tesla 1 started charging at midnight PW discharged at 5kW. Tesla 2 is set to charge at 3:00. It was fully charged off the grid. My 1 PW has its own sub panel with nothing exceeding 30A. The two chargers (and pool) are connected to the main panel with each having their own 50A. How do I separate the two? Can't I keep the PW for the house and exclusively use the grid for the teslas? What ate the rest of you Tesla+PW users doing? Oh - it is charged with a 7 kW PV system.

    Thanks!
     
    • Informative x 1
  2. Shygar

    Shygar Member

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    Aug 7, 2017
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    924
    Location:
    Pleasant Hill, CA
    That's what I'm trying to do. I only have one breaker backed up by my one PW2, but when I charged a rental Model X, it drew from the battery somehow. But I want it to leave the battery alone and only charge from grid. Getting my Model 3 soon so hopefully can do some more thorough testing, but from what I can tell it seems to be drawing from the PW as if it was solar.
     
  3. miimura

    miimura Well-Known Member

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    Los Altos, CA
    My EVSEs are powered from breakers in my main panel. The Powerwall installation cannot see those loads, so they do not drain to offset the EVSE load. Nothing special on my part, that's just how my installation was done.
     
  4. cwied

    cwied Member

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    It depends on whether you want the charger to be backed up or not. If you don't want it to be backed up, moving the CT so that it doesn't see the charger load would stop the Powerwall from trying to satisfy that load.

    The software way of accomplishing the same thing would be to set your backup reserve to 100% before the cars start charging. Alternatively, time-based control will also work to prevent your Powerwalls from discharging during off-peak hours.
     
    • Informative x 1
  5. SD Diver

    SD Diver Member

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    Location:
    San Diego
    Great info - thanks! I'm having the installer come by to look at that and will post the result. He says that Tesla recommended moving the CTs so that the monitoring software would see them. He did not think that that would cause the PW to try to back them up.
     
  6. cwied

    cwied Member

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    I just reread my post and realized I wasn't making complete sense. To be backed up, the chargers would have to be behind the gateway, of course. However, if the CTs are positioned so they see the charger load, I believe the Powerwalls will try to offset that load.
     
  7. miimura

    miimura Well-Known Member

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    Los Altos, CA
    To me, the best case is that the Powerwalls can see the load, but Time Based Control should prevent them from discharging if you're charging Off-Peak. However, most people don't have Time Based Control enabled yet.
     
  8. montreid

    montreid Member

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    Apr 6, 2016
    Messages:
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    Location:
    san diego,ca
    You have to move to backup only to prevent discharge overnight. We have a PV and PW2 on NEM 1.0. So, our MO is this ; 1130A: switch from backup to selfconsumption with a 70% floor as we want to charge up to 100% by 12n so all the peak solar production goes to the grid.

    As folk have mentioned, once Time Shifting program comes online, won't have to do this dance.

    With current ITC rules, no way to allow for charging directly at superoff peak rate --- shame. One could argue that folk should be able to discharge whatever they want during a surge ohmconnect hour especially. What better way for true x2G support for clean and grid stability.

    Imagine all the EVs plugging in during the 5-8pm surge --- no peaker plants needed.
     
  9. commasign

    commasign TeslaAdviceBlog.com

    Joined:
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    Messages:
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    Location:
    Davis, CA
    I have 4 powerwalls in backup only mode and a 20kW SunPower PV system. 3 Tesla wall connectors connected to the new main panel (power sharing 32amps, backed up by the powerwalls) and 1 Tesla wall connector connected to the old main panel (grid dependent, not backed up). In the event of the zombie apocalypse, should be enough power to be off grid indefinitely.
     
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