Powerwall 2 - Outage “Switchover” Delays?

[BrettS]

If so, and assuming there were a Scheduled Outage by the utility starting in the morning (~8am) and ending in the late afternoon (~5pm), would it be advisable to switch over to Self-Powered say 20minutes in advance of the scheduled outage and then revert to backup mode once said outage is over?

You certainly could do that. As I said above, in my experience, the switchover is still pretty minimal. The lights might quickly flash, but that’s about it. I personally probably wouldn’t worry about it. They say that it can take up to an hour for the powerwalls to switch modes, but it seems that it typically happens within a couple of minutes.

B) Given the PV is being instructed to “Shut Off” when an outage occurs due to there not being sufficient excess capacity in the PWs to absorb the excess PV production, what would be expected to occur should the home be drawing the full production of the PV AND drawing from the grid (i.e. the home electricity demand is higher than the current PV output in this moment) when an outage occurs in backup mode?

Whether the solar switches off depends entirely on the state of charge of your powerwalls. If you are in backup only mode, then your powerwalls should be fully charged. In that case, then when the outage occurs the solar will shut off and the house will be powered entirely by the powerwalls. After a short time, once the powerwalls get down to about 97% the inverters will come back online and your house will be powered by PV and the powerwalls, assuming that your house is still drawing more than the PV output. Or PV only if your house is drawing less than the PV output, with the excess going to charging the powerwalls.

However, if for some reason your powerwalls have less than a full charge (are at about 97% or less) at the time of the outage, then the inverters will not be shut off and solar will continue producing. If you are producing excess solar power and your powerwalls continue to charge, then the inverters will be shut off as soon as the powerwalls get up to about 98%, then once the powerwalls get back down to about 97% the inverters will come on again.

So just to clarify, we are saying that it’s normal for your inverters to shut off when an outage starts simply because you are in backup only mode and that keeps your powerwalls at a full charge.

 

[zƬesla]

One addition to what @BrettS said above, in an outage if solar produces more than 5kW multiplied by the number of PowerWalls (e.g., 10 kW for 2 PWs), then at a minimum the inverters will shutown and as some of us have experienced the whole house may go dark as well (i.e., PWs go off too).

 

[Freakyguy666]

You certainly could do that. As I said above, in my experience, the switchover is still pretty minimal. The lights might quickly flash, but that’s about it. I personally probably wouldn’t worry about it. They say that it can take up to an hour for the powerwalls to switch modes, but it seems that it typically happens within a couple of minutes.



Whether the solar switches off depends entirely on the state of charge of your powerwalls. If you are in backup only mode, then your powerwalls should be fully charged. In that case, then when the outage occurs the solar will shut off and the house will be powered entirely by the powerwalls. After a short time, once the powerwalls get down to about 97% the inverters will come back online and your house will be powered by PV and the powerwalls, assuming that your house is still drawing more than the PV output. Or PV only if your house is drawing less than the PV output, with the excess going to charging the powerwalls.

However, if for some reason your powerwalls have less than a full charge (are at about 97% or less) at the time of the outage, then the inverters will not be shut off and solar will continue producing. If you are producing excess solar power and your powerwalls continue to charge, then the inverters will be shut off as soon as the powerwalls get up to about 98%, then once the powerwalls get back down to about 97% the inverters will come on again.

So just to clarify, we are saying that it’s normal for your inverters to shut off when an outage starts simply because you are in backup only mode and that keeps your powerwalls at a full charge.

To be clear, are you 100% certain that IF the demand for Power from the home exceeds that being produced by the PV at time of outage the PV will still shut down in backup mode? This seems completely counterintuitive! Afterall, if the home is demanding power why wouldn’t the solar continue to attempt to fulfill that demand?

 

[Freakyguy666]

One addition to what @BrettS said above, in an outage if solar produces more than 5kW multiplied by the number of PowerWalls (e.g., 10 kW for 2 PWs), then at a minimum the inverters will shutown and as some of us have experienced the whole house may go dark as well (i.e., PWs go off too).

Wow! That is not something anyone on this thread has posted. How long does this last (“go dark”)?

 

[zƬesla]

Wow! That is not something anyone on this thread has posted. How long does this last (“go dark”)?

Long enough that everything in the house shuts down as PWs also go offline temporarily. See this thread for more details. Still working with Tesla certified installer to resolve as they are the ones that sized the system originally.

 

[BrettS]

To be clear, are you 100% certain that IF the demand for Power from the home exceeds that being produced by the PV at time of outage the PV will still shut down in backup mode? This seems completely counterintuitive! Afterall, if the home is demanding power why wouldn’t the solar continue to attempt to fulfill that demand?

Yes, I am 100% certain. As I said above, this is based entirely on the state of charge of the powerwalls. Briefly, the issue is that the system needs to be sure that all of the power that is being generated can be used. Because the house demand can fluctuate and the PV output can fluctuate (based on cloud cover and such) there is no guarantee that even if your house is using all of the PV output one minute that the next minute there won’t be excess power.

Normally when you are on grid any excess power can be sent back to the grid, but when you are offgrid that power needs somewhere to go and the place where it goes is into your powerwalls. However, if you are off grid and the powerwalls are fully charged, then again you wind up with a situation where there would be no place for any excess power to go.

For this reason whenever the powerwalls are fully charged (about 98% and above) the system will shut off your PV system. As soon as the powerwalls get down to 97% or less the PV system can come back on. Even if your home is using more power than your PV can provide this will happen because there is no guarantee that the sun won’t move out from behind a cloud or your air conditioner won’t shut off and then all of a sudden there would be excess power with nowhere to go.

When you are off grid (and only when you are off grid) and your powerwalls are fully charged the system will always turn your PV off, until the powerwalls can drain down a little to make sure they have capacity to store any excess power that may be generated when the PV is turned back on.

 

[BrettS]

Wow! That is not something anyone on this thread has posted. How long does this last (“go dark”)?

This is a different situation that most people won’t run into. Again, it has to do with excess power needing somewhere to go. This will only be a problem if you have a very large PV system and a very small number of powerwalls. Most systems are sized such that this is not a problem.

But, as stated above, charging powerwalls can accept a maximum of 5kW. So, if you had a huge 20kW PV system and only two powerwalls, then your solar system could generate up to 20kW, but your two powerwalls could only accept 10kW. If the solar system was generating more power than the powerwalls could accept then the whole system could shut down to prevent a dangerous failure.

However, in the above example, if you had four powerwalls instead of two, which is likely if you have such a big solar system, then you would have no problem as the four powerwalls could accept the full 20kW output of the PV system.

Also, even if you do have an unbalanced system where this could happen it would only happen when you are off grid, because when you are on grid any excess power can be sent to the grid.

There are also other ways to work around this, such as ensuring that only some of your PV system will be active during a grid outage to make sure that you can’t generate more power than your powerwalls can handle.

 

[bkp_duke]

One addition to what @BrettS said above, in an outage if solar produces more than 5kW multiplied by the number of PowerWalls (e.g., 10 kW for 2 PWs), then at a minimum the inverters will shutown and as some of us have experienced the whole house may go dark as well (i.e., PWs go off too).

I wonder how this works with microinverters. Do some panels get shut down, or does the control system just turn down all panels?

 

[BrettS]

I wonder how this works with microinverters. Do some panels get shut down, or does the control system just turn down all panels?

The system will shut down all the inverters at once. The way it does this is by raising the line frequency from 60hz to signal the inverters to shut down. It can’t communicate directly with the inverters, nor does it even know how many inverters are in the system.

There are some protocols available with newer inverters that allow them to scale back production as the frequency increases, rather than just shut off at a certain level, but it seems like tesla does not generally configure this option.

(And in my opinion, at least, there’s not really a strong reason to as the end result is pretty much the same either way. Either the PV system runs at partial capacity constantly or it runs at full capacity for some of the time and turns off for some of the time. But in the end the same amount of power is generated.)

And again, just to be clear, this only happens when you are off grid. When you are on grid any excess power can be sent to the grid, so there is no need to turn off or scale back the PV system.

 

[bkp_duke]

The system will shut down all the inverters at once. The way it does this is by raising the line frequency from 60hz to signal the inverters to shut down. It can’t communicate directly with the inverters, nor does it even know how many inverters are in the system.

There are some protocols available with newer inverters that allow them to scale back production as the frequency increases, rather than just shut off at a certain level, but it seems like tesla does not generally configure this option.

(And in my opinion, at least, there’s not really a strong reason to as the end result is pretty much the same either way. Either the PV system runs at partial capacity constantly or it runs at full capacity for some of the time and turns off for some of the time. But in the end the same amount of power is generated.)

And again, just to be clear, this only happens when you are off grid. When you are on grid any excess power can be sent to the grid, so there is no need to turn off or scale back the PV system.

Ok, taking this further . . . I have 4 "zones" in my SunPower system, the equivalent of lines. I wonder if the system would be smart enough to raise the line frequency on just one or two of them and do a partial shutdown (probably not).

 

[MorrisonHiker]

Ok, taking this further . . . I have 4 "zones" in my SunPower system, the equivalent of lines. I wonder if the system would be smart enough to raise the line frequency on just one or two of them and do a partial shutdown (probably not).

I have 3 Delta Solivia inverters and 1 SolarEdge inverter. Often when the Delta Solivia inverters are offline, I see that the SolarEdge inverter is still online and producing power. I'm guessing the shutoff frequency threshold is configured differently, allowing the SolarEdge inverter to stay online while the three Delta inverters are shut off.

They could probably accomplish something similar with your system if the inverters had different shutoff frequency thresholds configured on each inverter...but I don't know if they regularly do that.

 

[bkp_duke]

I have 3 Delta Solivia inverters and 1 SolarEdge inverter. Often when the Delta Solivia inverters are offline, I see that the SolarEdge inverter is still online and producing power. I'm guessing the shutoff frequency threshold is configured differently, allowing the SolarEdge inverter to stay online while the three Delta inverters are shut off.

They could probably accomplish something similar with your system if the inverters had different shutoff frequency thresholds configured on each inverter...but I don't know if they regularly do that.

It was more of a theoretical question. There is simply no way my 12 kw SunPower system can overload the 4 powerwalls attached to it.

 

[BrettS]

Ok, taking this further . . . I have 4 "zones" in my SunPower system, the equivalent of lines. I wonder if the system would be smart enough to raise the line frequency on just one or two of them and do a partial shutdown (probably not).

The short answer is no. The system really isn’t smart at all. All it does is raise the line frequency as the powerwalls approach the maximum state of charge. The frequency needs to be the same on everything connected to your house, so even if it was smart enough to, it couldn’t raise the frequency on some of the lines and not on others as that is not technically possible.

However the long answer is... sort of. When it raises the frequency it does so slowly. It will start at 60Hz, of course, then as it gets to about 98% full it raises the frequency to 60.1Hz, then it continues all the way up to the max (which defaults to 65Hz, but can be lowered by tesla to 62.5Hz. So theoretically it would be possible to program two of your inverters to shut off at, say, 60.5Hz and the other two to shut off at 61Hz, and in that way it could control the inverters somewhat independently. However, as I said above, in the end it’s probably more effort than it’s worth because the end result would be the same in terms of the amount of power produced.

 

[miimura]

To be clear, are you 100% certain that IF the demand for Power from the home exceeds that being produced by the PV at time of outage the PV will still shut down in backup mode? This seems completely counterintuitive! Afterall, if the home is demanding power why wouldn’t the solar continue to attempt to fulfill that demand?

The solar inverter will see the power interruption. Depending on how it's configured for "ride-through" it will probably stop production and wait for its timeout period, frequently 5 minutes, before it starts producing again. Regardless of PW state of charge, it is common for the solar to go offline for 5 minutes after an grid outage event. This is the same for string inverters and micro-inverters.

 

[bkp_duke]

The short answer is no. The system really isn’t smart at all. All it does is raise the line frequency as the powerwalls approach the maximum state of charge. The frequency needs to be the same on everything connected to your house, so even if it was smart enough to, it couldn’t raise the frequency on some of the lines and not on others as that is not technically possible.

However the long answer is... sort of. When it raises the frequency it does so slowly. It will start at 60Hz, of course, then as it gets to about 98% full it raises the frequency to 60.1Hz, then it continues all the way up to the max (which defaults to 65Hz, but can be lowered by tesla to 62.5Hz. So theoretically it would be possible to program two of your inverters to shut off at, say, 60.5Hz and the other two to shut off at 61Hz, and in that way it could control the inverters somewhat independently. However, as I said above, in the end it’s probably more effort than it’s worth because the end result would be the same in terms of the amount of power produced.

I don't have traditional inverters, everything is on a control system, and all 36 panels have microinverteres. I presume to make this work, in theory, the control system would need to see the line voltage increase and be programmed at certain frequencies to drop first one string of panels, then the second at a step higher frequency, and so on until all 4 strings are shut off. I doubt that SunPower's PVS5x control system is that intelligent.

 

[jboy210]

I have 3 Delta Solivia inverters and 1 SolarEdge inverter. Often when the Delta Solivia inverters are offline, I see that the SolarEdge inverter is still online and producing power. I'm guessing the shutoff frequency threshold is configured differently, allowing the SolarEdge inverter to stay online while the three Delta inverters are shut off.

They could probably accomplish something similar with your system if the inverters had different shutoff frequency thresholds configured on each inverter...but I don't know if they regularly do that.

On my Delta M series inverters, it shows a max operating frequency of 60.5 Hz. So, for at least M-series Deltas, the range is pretty tight. It might be similar for your Solivia's.

 

[woferry]

My 2019 Solivias definitely just stop as soon as the frequency exceeds 60.5Hz (no curtailment), and do not start again until the frequency has been 60.5Hz or less for over 5 minutes. I'd have hoped that maybe the newer M-series units were 'better' in this regard, but perhaps not. At least for the Solivias Tesla seems to use a custom unit, the PCB inside looks nothing like what's in the Solivia manual, and Delta told me my unit is specific for Tesla. Not sure if it's the same for the M-series.

 

[jjrandorin]

Wow! That is not something anyone on this thread has posted. How long does this last (“go dark”)?

@zTesla is talking about a very specific situation that wont happen to most people, as long as their system is configured correctly for the number of powerwalls they have.

Rather than go into the details of that specific issue (there are a couple of threads with discussion on it here I could find if you want to read them) just know that you are not likely to be impacted at all by that issue if you have 1 powerwall for each approximate 5kW of Solar you have. Even if you have slightly more solar than that (for example, 11kW of solar and 2 powerwalls, its ""unlikely" you would be impacted by that specific issue, but the more PV you have that is more than approximately 1 powerwall per 5kW, the more likely you run into the issue he is saying.

Even then, if the system was designed as 1 powerwall and 12kW solar, then the PV should be designed to shut off part of your solar in an outage to not run into the specific issue he is talking about.

The TL ; DR version on that specific issue is, its unlikely you would be impacted by it (but if you have a large solar install with only 1 powerwall, its likely that part of your solar has been configured to simply not run at all in an outage.. again, specifically if you have more PV than approximately 1 powerwall per 5kW).

 

[jjrandorin]

To be clear, are you 100% certain that IF the demand for Power from the home exceeds that being produced by the PV at time of outage the PV will still shut down in backup mode? This seems completely counterintuitive! Afterall, if the home is demanding power why wouldn’t the solar continue to attempt to fulfill that demand?

Here is what I believe would happen.

Scenario

Powerwalls in backup only mode, and full at 100% charge. PV powering home and providing more power than home needs to run. Excess PV feeding to grid.

Power outage (either utility, or simulated by throwing main breaker)

Gateway triggers powerwalls to provide home power, and raises frequency to shut off PV. Home load provided temporarily by PWs.
Powerwalls drain to 96-97%,
Gateway lowers frequency and PV comes back online. If PV > than house load, excess PV fills batteries until batteries full. If batteries get full again, Frequency raised to shut down PV, until batteries back below 96-97% at which point PV comes on.. cycle repeats.

If PV < than house load when it comes back on after the initial shut down / swap over, then PV stays on, provides power to home, while powerwalls make up the difference and slowly drain since they are being used.

I believe in all cases, that first swap over with batteries at 100% and PV, would trigger the powerwalls to shut down.

To touch on what zTesla is talking about, if, for example, you had a very large PV system and not enough powerwalls, if you had an outage, if you have (lets say) only 2 powerwalls, and the home load at the time was 15kWh, if you had a power outage, your 2 powerwalls can only provide 5kW each (7kW in a burst but only for a very limited time). Since your home load would be 15kWh, it would be more than your powerwalls could provide, and the "system would shut down".

This would only happen if you had 15kWh of load on the backup side though, where that is unlikely to happen. What is more likely to happen is, some of those loads when you are drawing 15kWh are likely on the non backed up side, so would be shed when the power went out, and those items simply wouldnt work.

If someone installed whole home backup with only 2 powerwalls, but the two powerwalls were not enough to run the backup loads, then that could happen but that is rare, and would be based on individual mistakes in the design of that system.

 

[zƬesla]

To touch on what zTesla is talking about, if, for example, you had a very large PV system and not enough powerwalls, if you had an outage, if you have (lets say) only 2 powerwalls, and the home load at the time was 15kWh, if you had a power outage, your 2 powerwalls can only provide 5kW each (7kW in a burst but only for a very limited time). Since your home load would be 15kWh, it would be more than your powerwalls could provide, and the "system would shut down".

Note that this is slightly different than what I referred to. In my case,with 2 PWs, PV - House > 10kW. So, house load around 1 to 2kW, PV generating 13-14kW, PWs shut down. You seem to refer to a large house load which was not the case.