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Does PW vary battery charge rate depending on load from grid?

Discussion in 'Tesla Energy' started by Icepicknz, Jul 19, 2018.

  1. Icepicknz

    Icepicknz Member

    Joined:
    May 19, 2018
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    Location:
    Auckland new zealand
    Hey guys.

    I have 2 tesla powerwall2, in backup mode it charges from the grid at ~1.7kw per pw, so 3.4kw for the 2.
    In ToU setting it charges from the grid at about 6.4kw for the 2 powerwalls.

    In New Zealand (and australia I believe and perhaps the UK) the max feed in for residential is 63A on single phase, if you have 3 phase, its 3 x 63A feeds; your power wall is connected to a single phase.

    If I plugin my Model X to charge, its 7.5kw + powerwalls 6.5kw thats 14kw; if my spa pool happens to turn on (does so every 2-3 hrs to keep it warm) thats another 2kw of power and then say the oven or stove ~3kw.

    The load all added up on ToU setting will take me over 16kw which is the max feed in from the grid; does the Tesla PW monitor the load usage and lower its charging rates in this situation, or is it going to pop the fuse in the street?

    Look forward to hearing from you
    Barry
     
  2. Shygar

    Shygar Member

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    Location:
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    Max each powerwall can charge/discharge is 5kW, so if you have two it's 10kW. I have noticed though that as it's getting closer to your reserve percentage, the usage drops from 5kW to lower amount (I only have one powerwall). As you mentioned it's only 1.7kW if you are in backup mode, 5kW for all other modes.
     
  3. Icepicknz

    Icepicknz Member

    Joined:
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    Location:
    Auckland new zealand
    Sorry Shygar, i think you mis read my question.

    My feed in from the grid is only 63Amps (~15kw). Does the power wall have any smarts not to charge at its full rate when other loads (charging car, spa pool, oven etc) are using the grid, as if I exceed ~15kw from the grid, it will pop the fuse in the street and I will have to call the power company to come change it.
     
  4. cwied

    cwied Member

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    Location:
    San Mateo, CA
    Somebody from your region may have to comment on this issue, but the Powerwall does measure house load and does have ways of managing charging to manage house load. Whether they handle this case, I don't know. I have seen in the Wizard that they do handle a maximum feed-in rate, so that would be a very similar operation. There's no question that they could do it if they wanted to.
     
  5. Icepicknz

    Icepicknz Member

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    Location:
    Auckland new zealand
    Thanks @cwied ; the wizard for NZ doesn't show max feed in but does have a max export. When you select NZ it does state the frequency and voltage, so I suspect maybe they have set the max AMPS from grid.

    I just don't want to be in a situation of ToU where we cooking dinner late one night at 8:59pm, spa is going, car is charging and then my off peak 9pm comes along and the power wall starts charging at 6.5kw and trips my mains fuse outside and I have no power till they come fix it.

    I have sent a question to tesla to ask and will revert here for anyone looking in the future
     
  6. cwied

    cwied Member

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    Sorry, I used the wrong term from memory. It sounds like the Wizard is identical.
     
  7. Ampster

    Ampster Member

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    Sonoma, California
    I think this is a question for your installer. Also, I am not sure what you are referring to as "a situation in TOU"? In my area TOU is a rate structure based on time. It doesn't have any relationship to loads. It is designed to discourage load scenerios like you mention, during times of high grid usage.
     
  8. CA-Gbm84

    CA-Gbm84 Member

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    Oct 22, 2017
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    Location:
    Bay Area
    I think you are getting mixed responses - 'Feed in' usually refers power flow from home -> grid. Ie 'Feed-In Tariff'. That is what cwied was referring to.

    What you are describing is a maximum total home load (home + PW grid charging), where power flow is grid -> home.

    It sounds like that maximum is 63A (15kW) for your home. Currently Powerwall will not manage your maximum grid load.

    A simple feature would be to limit Powerwall grid charge power based on a set variable of total grid load (63A). This could be done in a grid code if every home is the same. However, it would probably make more sense to be a variable set during commissioning to allow for individual preferences.

    Even smarter would be for Powerwall to monitor and discharge to protect you going over that limit.
     
  9. cwied

    cwied Member

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    The one thing I would say is that it's known that the Powerwalls operate differently in different regions. I wouldn't necessarily assume that they don't have support for something like this just because the California Powerwalls don't do it. I meant to use the export/feed-in restriction as an example of their doing something similar, albeit in the opposite direction.
     

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