Solar Panels

logic for where power goes-house or walls/storm mode

My 11 KW system just got installed in FL. The two-way meter is not in yet, but I was advised to run the system to charge the two power walls. I am also experimenting with the grid power turned off to get an idea of how well it can backup the house during an outage.

My big question at the moment is how it splits power from the panels to the walls. When I am off grid, according to the app, it is frequently turning off the panels and running the house on the power walls. The power walls are at 85%. I would really like to see it charging rather than expending them. It happens in both the backup and the self-powered mode and with the sun out or behind a cloud. I don't see a way to control it. I realize that if the panels are not producing enough to run the house, it will pull with the power wall and I have seen that happen with energy still flowing from the panels. What I am seeing, however, is the panels off for up to five minutes at a time.

Also, there is supposed to be a storm mode available. It is not on my menu. My understanding it that it would top off the power walls with grid power if a storm is forecast. Did this feature go away or was it eliminated to maintain the tax credit?

Thanks for any help.

Comments

  • StormWatch does not appear on your app at the beginning. It just appears after a couple of weeks (and is dependent on the version of firmware installed). Firmware updates are also essentially invisible and just show up. Be patient on that one...
    The turning off of the solar is an intended feature when off grid. As the batteries near full charge and the house is not consuming the full output, the frequency output of the powerwalls shifts a bit to kill the inverter. There are multiple threads in the "Energy Products" section on this.
  • Thanks! I understood it would turn off solar when batteries are full, but was surprised to see it at these charge levels. It was still happening when I let the power walls drop to 70%. I also was surprised to see it exporting power to the grid when the power walls were at 70%. I had assumed the power walls could take at least 6-7 KWh in charge, but they seemed to max out at a bit over 5 KWh in backup mode. The only reason it matters at the moment is I don't have the two-way meter, so I should not be sending power out.

    Is there anyway to manually put it in the storm mode, or is that totally dependent on Tesla's interpretation of weather reports?
  • StormWatch is not under your control (other than to simply turn it off). No way to implement StormWatch as a user.
  • > @Jones_lab_guy said:
    > StormWatch is not under your control (other than to simply turn it off). No way to implement StormWatch as a user.

    Thanks!! Too bad, but I guess it would be abused.

    I am still puzzling why it would send power to the grid when the power walls are not full. Once I can go online for real, I will be watching it. It would be nice to understand the logic it uses for where to send power in each mode. I would like to be able to prioritize whether it goes to the house or the battery. I generally want the battery full, but could also see situations to prioritize the house.
  • At noon with full sun, for me, solar will be powering the house, charging the Powerwalls, and exporting to the grid. For me, my two Powerwalls take a peak charge of about 5 kW - but that is limited by solar production and power used by the house. I think I've gotten up to 7 kW charge rate on some days, but not recently.

    Solar production priority is first power the house, then charge the Powerwall, and if any left-over send the excess to the grid. Once the Powerwalls are at 100%, it then diverts all excess beyond house use to the grid. I find it generally does the right thing. With low solar lately (due to fires/ash here in CA), I don't get to 100% PW charge.
  • I had to increase my reserve to 60% to compensate for lower production due to smoke and ash. I also narrowed my peak times from 3PM to midnight, to 4PM to 9PM. (I had previously widened peak to be kinder to the grid during the heat wave.) Now, because I start the morning at 60%, I can get to 100% before 4PM, although it's close. My reserve was 30%, previously. I figured these moves were prudent, as the odds of losing the grid are significantly higher right now.

    April and August are typically my best production months, but this August is terrible, because of the fires.
  • I should have written September, instead of August. My bad.
  • Similar to @gregbrew, changes to the settings are dynamic. Different production in winter versus summer dictates different reserve values for me by season. Also, like others above - the threat of fire, ash cover on the panels and a host of other inputs may cause changes to my settings. It is possible to micromanage the system (which I actually do - OCD I guess). Main goal for me is to make sure that I always have sufficient reserve to reach the next production day. Philosophically, I also try to be kind to the grid as much as possible after I have addressed the primary goal of "don't lose power or my wife will kill me". HaHa.
  • I understand that with 1 PW in backup mode (grid outage, at night no sun) all my non-backed 3phase appliances (aircon, well pump, dryer, oven, pool pump...) are off. I guess it is the same in off grid mode too when the sun is up? The sets of non-backedup and the 3phase appliances seems to be the same set.
  • I still don't understand your use of the term "3phase". Unless you live in an industrial building, you likely don't have three-phase power. I suspect you're using the wrong term for a residential 240V AC split-phase feed. If so, it is never called "3phase", as that means something quite different. If you want to differentiate between "120V" AC devices that use one leg of the feed, and "240V" AC devices that are across both legs, just use those descriptors.

    BTW, my Powerwalls each independently feed both legs of the split-phase 240V AC. A single Powerwall should feed your entire house (both 240V legs) just fine. It could possibly struggle with the inrush currents on unusually large inductive loads, but inrush limiters on those devices can solve the problem for a few hundred bucks. Besides, based on the list of devices you specified, a single PW likely isn't going to meet your needs anyway.
  • @greg - You may be right. I was assuming those that use 3-phase are in Europe, where residential 3 phase is common. You never see it here in the USA.

    A close friend here in the USA has a huge 3-phase milling machine in his garage. He has an electronic converter to use the house split-phase to power it. I also think all the Superchargers run on 3-phase power. It's one reason you can't have a Supercharger in your house, aside from the crazy high price!
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