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PowerWall tips for when grid is out!

PowerWall tips for when grid is out!

Hi,

I have 3 PW2 being installed this week and I should be online tomorrow. :)

In my installation, I opted for wholehouse protection and the PWs should be more than enough for 12 hrs+ without any compromise on my appliances and heatpump.

Question: For scenarios where the cars are plugged in and utility power goes out, is the Tesla App smart to trigger a command to the cars to stop the charging process? I certainly could do it manually, but thinking on scenarios when there is no one home.

If answer is no, I have sketched a little system already to solve for this (a sensor + app on raspberry pi that will trigger a stop charge command to the cars)... but I really would like to avoid geeking out on this one. :)

Thanks.

markbraukman | July 9, 2019

I don't think so. I've not had a power outage when my MS is charging. When I have lost utility power, the PWs kick in. I would think that if my MS was charging at that time, it would drain the PWs and then all would go dark.

Tesla-David | July 9, 2019

The Tesla app allows us to stop or initiate charging on our MS and M3 easily to manage our 2 PW2’s integrated with our 13.2 kWh solar PV system. We operate in self powered mode with our backup set at 25 percent, and have been sel sufficient since mid February with our setup, not utilizing any grid energy. We try to time our Tesla charging when we have full solar so as not to drain the batteries, and usually stagger charging of our MS and M3.

Tesla-David | July 11, 2019

I meant to add in response to OP's question, the Tesla app will not stop your EV charging when the power goes off, but you can do so easily from the Tesla app. Obviously if the power goes off you want to turn off as many energy draining applications as possible to preserve the PW2's for essential stuff. I summarized above how we stagger our Tesla charging when the sun is out to maximize the efficiency of the PW2's.

mrburke | July 13, 2019

Question from someone who does not have the system configured yet. (Waiting for Tesla to get back to me.)

While two PWs are enough to handle my houses total electrical load, it likely that charging my car are 40 amps could overload the 60amps that I believe the two PW can produce when I factor in other household loads.

While, I am happy to manage my loads manually, will I be required to put the charging circuit on a separate panel that is not backed up from the PWs ?

Thanks in advance.

gregbrew | July 16, 2019

When the grid goes out, flip the Main breaker in your electrical panel, to isolate your system from the grid. Grids are notoriously "dirty" in outages, and can drive the TEG bonkers. It happened to mine.

Once you're sure the grid is back up (and clean), restore the main breaker.

Tesla-David | July 17, 2019

@mrburke responding to your question about whether 2 PW2’s will be able to handle your home loads and Tesla charging. For us the answer is yes, but we limit the charging to 25 Amps to keep the batteries from draining down, and stagger our charging for both Tesla’s. This has worked for us over the past 13 months. See my summary above. We could manage a higher charge rate, but that would trigger grid draws, which we are trying to avoid.