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Increased Backup Reserve



Yesterday was very stormy, very little sun made it thru in the morning so after charging my car after lunch the battery was down to 15% (usually it'd be in the 90s). There was so much cloud coverage after lunch that no solar power was produced for the rest of the day, so the battery did not gain any additional charge.


From the afternoon on we lost power 3 times. Each time everything kept running with the exception of the AC unit. Just 1 Powerwall is not enough to run it, nor the 50 amp car charging outlet, so circuits for both were relocated to a new breaker-box which cannot be powered by the battery; though, as by the big green spike in the screenshot above, the battery can assist with those provided the grid is up. If I had a second Powerwall the AC and car charging would be supported without the grid.


This morning battery was at 12%. Forecast is storms for at least thru next week Thursday.


Due to likelihood of sporadic solar power and additional power outages during this time, I decided to bump the backup reserve to 50%.


There's some sun this morning and the battery is using all available solar to charge, while the house is exclusively using the grid.


Even with the current cloud cover enough sun is getting thru to generate 0.7 kW, and the battery's up to 17%.




A) circuit breakers for the Solar and Powerwall:


B) Main panel, can be powered without grid:


C) New sub (side?) panel, requires grid:



Trying to keep the Houston heat out of the house while charging car via dryer outlet


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So the solar system is not a perfect solution. We still need electricity companies.


Of course, the electricity bill will be lower since the solar panels are used.


The best use of solar system is to live in the desert. Or hot areas like California.

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Personally I'd think that having all 240V circuits grid only would make sense as those are typically power hungry and would quickly drain the batteries.

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Battery's at 75%




Additional photos added for the rest of this comment.


The battery's breaker is 240v 30 amp, the panel's is 240v 32 amp.


I do have one 240v circuit that's still in the main panel - the dryer outlet. I have a gas dryer so don't use it, but have used it in the past to charge the car when the 120v outlet wasn't enough. Not convenient as it's in the house, so have to deal with Houston heat trying to get in.


I could see utilizing it during an extended outage to charge the car provided:

  • Powerwall was full
  • Sun was out without any cloud cover, meaning I could produce more than the house would use

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Yep, charge the car before dumping the excess power back into the grid. It's interesting the power controller doesn't have a circuit specifically for PEV charging.

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Yeah, converting DC -> AC -> DC to charge the car battery isn't the most efficient, but having to run DC to the garage would complicate the installation.

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I hadn't thought of the AC conversion losses, but running high voltage high current DC lines would probably eat into most of the short term savings. And unless you're going to feed it with a dedicated 240V 100A circuit you're probably not going to see much benefit from a charging time perspective.


I'm just thinking that there would be value from the power controller perspective to have a dedicated PEV charging circuit so it can best manage it. And it's a Tesla PowerWall - shouldn't it have a place to plug in your Tesla?

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