I havent experienced it (my solar is not big enough, since I have 2 powerwalls and 8.7kW of solar), but I also seem to remember someone saying that it would have to sync to the grid to restart. I havent ever turned either of my powerwalls off since install. If you are going to test it (which would be interesting), I would make sure you are at a point in time where you could be without power for as much as 5 minutes.
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Just Ordered 16.32kW w/2 Powerwalls
- Thread starter Southpasfan
- Start date
I havent experienced it (my solar is not big enough, since I have 2 powerwalls and 8.7kW of solar), but I also seem to remember someone saying that it would have to sync to the grid to restart. I havent ever turned either of my powerwalls off since install. If you are going to test it (which would be interesting), I would make sure you are at a point in time where you could be without power for as much as 5 minutes.
I think gpez was talking about yet another issue, which was the possibility that the draw from the house exceeds the ability of the powerwalls during a "powerwall only power situation." I think I saw an extensive thread on this having to do with the draw that occurs on starting up an A/C unit.
Swerving back to my issue, it sounds like 3 powerwalls at 5kw each cover the 16.32 system. It does not look like, from the live data I am seeing from my neighbor, that a 16.32 system will ever exceed 15kw, so the forced complete shutdown scenario with no option to cycle on would be avoided.
3 Powerwalls also, of course, make the system that much more likely to be self sufficient, as its much more cushion to make it through a night with 40 kwh as opposed to 27kwh.
Plus in an extended outage those extra 13.5kwh might be significant. Even though I do not live in extended outage territory.
Re reading back through my posts in this thread, they come across quite a bit more aggressive than I intended, so I apologize for that. I was also not intending to argue, etc.. just help.
The official Tesla Powerwall FAQ does not specify that it is only one or the other just that it's "power" so I'm not sure how you're drawing that conclusion. In fact the Powerwall datasheet specifies that the 5kW continuous max power is for both charge and discharge. There is a single inverter that provides this functionality and tripping it by charging or discharging is the same.
@power.saver Could you please cite the source for this statement (specifically the bolded part) as it is not confirmed in any of the official Tesla literature I've seen.
Nope
I believe that FAQ referrs to both charge and discharge limits.
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Yeah, I think 3 powerwalls would be perfectly fine for you. Also, remember that to overload it would take 15kW going to the powerwalls, plus whatever your house was drawing at the time. My house rarely goes below 1.6kW during the day and is often closer to 3 or 4kW when the AC is running, so even if your house was only drawing 1kW that would mean that your solar system would have to exceed 16kW before you had a problem with three powerwalls. That would give you even more of a buffer.
Most people never even bother with this, and in this case I didn't see them as that aggressive, especially since I was asking the same question multiple times in different ways.
Which is always annoying, when it comes right down to it.
I was told this by the Tesla lead installer that did my system. I had solar before getting PWs, and the original design was to have all 3 inverters on 2 PW. But the Tesla lead installer said that would not be safe, and explained to me what would happen in the event of a solar power overload. So we relocated one inverter outside the backup circuit to explicitly prevent it from occurring. This Tesla lead installer had seen it happen at a previous install where they had to go back and fix it, and he didn't want the same thing happening to me.
Gotchya. Of course I could be wrong however based on my understanding, conversations with my installer, and the public documentation Tesla provides I believe you were given erroneous information about how the Powerwall behaves in this scenario.
Out of curiosity was that an actual Tesla installer (Solar City) or a certified installer?
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They were actual Tesla employees from the Tesla Energy Atwater Village office, not a Solar City or other certified installer.
Personally I would go back to Tesla and challenge that because it does not make sense and is not documented anywhere. My installer (local certified) worked closely with Tesla on my install and had no problem with the 8.55kW PV and single Powerwall configuration I have.
Well I suppose on a sunny day with solar power at max and minimal house loads, you could open the main breaker and see what happens.
I'm tempted to
We've had crummy days here and the forecast for the next week+ isn't great. I've been meaning to do some off grid testing anyway.Let’s not have anyone try anything
This line of inquiry got started when someone pointed out that my ordered system, 16.32 with two powerwalls, was a powerwall short because it would, in an actual outage, likely shut off.
After quite a bit of back and forth, this much is clear (1) a 16.32 system could easily produce more than 10kw and (2) two powerwalls have a. 10kw Max input and output so (3) the whole system would shut down, as if you didn’t have any powerwalls.
I think Brett summarized it best a few posts ago why this would happen, when he compared a forced shutdown caused by too much power for the powerwalls to take for even one instant with managed on and off cycling based on real time draw.
This line of inquiry got started when someone pointed out that my ordered system, 16.32 with two powerwalls, was a powerwall short because it would, in an actual outage, likely shut off.
After quite a bit of back and forth, this much is clear (1) a 16.32 system could easily produce more than 10kw and (2) two powerwalls have a. 10kw Max input and output so (3) the whole system would shut down, as if you didn’t have any powerwalls.
I think Brett summarized it best a few posts ago why this would happen, when he compared a forced shutdown caused by too much power for the powerwalls to take for even one instant with managed on and off cycling based on real time draw.
pdx_m3s
Active Member
You would want to ask your installer, but if you use enough power to want a 12k system, I suspect that you would be fine with 2 powerwalls with that size system.
It appears systems can produce, in their best hour, about 85% of their rating. A 12kwh system would be right at 10kw plus 1kw for the hike so two PWs with 10kw capacity are fine by the math.
But that’s why my ordered 16.32 would not be fine by the math. Because if there are only 2 PW the house would need to be pulling almost 4kw (85% of 16.32 is 13.87.
Hence the concern spotted by, I believe, Drsmilie many posts ago.
But that’s why my ordered 16.32 would not be fine by the math. Because if there are only 2 PW the house would need to be pulling almost 4kw (85% of 16.32 is 13.87.
Hence the concern spotted by, I believe, Drsmilie many posts ago.
pdx_m3s
Active Member
And inverter rating. Is the ~12kw panel rating or inverter rating? The latter matters more.
Yes, and - as has been mentioned in this thread and elsewhere - the cloud edge effect (forget who introduced the terminology me in a different thread - thanks) can cause significant spikes beyond the normal maximum. With limited monitoring so far, I have seen spikes up to about 40% above the normal maximum power I would expect to see (and hitting right at the limit of my inverter.) I've seen the spike decay back to the expected levels within a minute or two, but it is unclear whether that would be fast enough to not cause an issue for the system (noting that PWs are rated for a surge that also happens to be 40% above normal) if it was designed with little tolerance.
