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Powerwall 2 functionality question

Discussion in 'Tesla Energy' started by dutchinchicago, Jul 27, 2017.

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  1. dutchinchicago

    Joined:
    Oct 12, 2015
    Messages:
    61
    Location:
    Chicago
    Is it possible to set the powerwall 2 to charge to 80% between 1 and 3 am and then starting at 6 am start discharge when there is a need for electricity and store and excess solar power during the day (when possible)?

    I don't want the battery to discharge during the night when power is very cheap and my car is charging?

    Is there any kind of manual available yet?

    I got an e-mail that powerwall 2 installations start in August in my region (Chicago).
     
  2. SolarRyan

    SolarRyan Member

    Joined:
    Mar 13, 2015
    Messages:
    7
    Location:
    Sacramento, CA

    Yes
     
  3. PlugNPlay85

    PlugNPlay85 Member

    Joined:
    May 20, 2016
    Messages:
    35
    Location:
    Oahu
    Currently there is no option to set specific times to charge and discharge.

    Solar will always supply the home demand first, then any excess will charge the PW.

    There are currently 2 modes, Self Powered and Backup

    Backup mode is strictly that, backing up your whole home or circuits you select at time of installation.
    Charging in backup mode will charge your PW to 100% using excess solar and power from the grid. PW can only charge at 5kwh max so any excess coming from solar will go back to the grid.

    Self Powered mode allows you to set a reserve to the PW's percent of discharge. Again solar will power the home demand first, if the home demand is higher than solar can provide then PW will start to discharge. If demand is too higher for Solar and PW then the grid will make up the rest.
    Charging in Self Powered mode has a few scenarios

    PW charge % lower than set reserve %
    PW will be charged using solar and the grid to get to the reserve % as quickly as possible. When reserve is met, strictly excess solar will be used to charge till 100%

    PW charge % higher than set reserve %
    PW will discharge if home demand is higher than solar production. Excess solar will go to the grid.

    So you are able to get the PW to charge and discharge at certain times but you need to play with the reserve to meet your needs. According to Tesla, an update will come out to allow time - of - use or TOU and load shifting to be accomplished. Hopefully in the next few months.

    One thing to note, the PW are capable of discharging at 5kwh continuous. Having your water heater and stove on at the same time will most likely exceed this. I have two PWs so this allows for 10kwh continuous which is better suited for whole home backup / off grid use.

    Regarding the manual, it is very simple. It does not explain a lot.

    Hope this all helps
     
    • Informative x 1
  4. ReversePolarity

    Joined:
    Nov 13, 2014
    Messages:
    51
    Location:
    Los Angeles CA
    How does the PW complement with PV + TOU rate plan?

    My PV's are selling back @ ~0.3/kwh in the day and buying at 0.1/kwh at night (charging the car) ... so if the pw takes the daytime electricity that would have been sold back to the grid at .3/kwh to charge my car and reducing amount of $0.1/kwh electricity that would be bought back, I feel that my electricity bill will go up =X

    Unless something is completely wrong with my calculations...
     
  5. PlugNPlay85

    PlugNPlay85 Member

    Joined:
    May 20, 2016
    Messages:
    35
    Location:
    Oahu
    I think it depends what your TOU looks like. I have PV and a TOU rate plan.

    My TOU is
    9am-5pm $0.128 per kwh
    5pm-10pm $0.35 per kwh
    10pm - 9am $0.22 per kwh

    Currently my solar produces about 24 - 26 kwh but my home uses a total of ~ 60 kwh daily. This is due to AC running all day with electric range and water heater and a family of 6

    Remember, your PV will power your demand to your home first then any excess will charge the PW in self powered mode. If you place PW in backup mode, it will use both grid and excess solar to charge. If there is no excess solar than charging will be done from the grid.

    The ideal situation would be to have a PV system producing enough to supply the home demand and also charge the PW at max input.

    My string inverter PV system is limited by usable roof space and shading, I am currently seeing if using power optimizers and a solaredge inverter will help to harvest more power during the day.

    I cycle my PW like this...

    I charge the PW in backup mode from 7am till about 2pm. Solar supplies the house and excess solar charges the PW. If the solar is not enough to supply then the grid will charge the PW at 12 cents / kwh

    I then put the PW to self powered mode from 5pm till 7am which would pretty much bring the PW to 0% then repeat the process

    Any excess solar goes back to the grid from 2pm since the PW is at 100%
     
  6. dutchinchicago

    Joined:
    Oct 12, 2015
    Messages:
    61
    Location:
    Chicago
    Thanks for the detailed reply. Tesla energy support chat confirmed that TOU time shifting and self consumption will be mutually exclusive modes.

    I am in the same situation that my solar covers about 30% of my daily use. I would love to self consume as well as take advantage of TOU cheaper rates. Maybe a future update will cover this.

    Paul
     

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