zanydroid
Solar Wizard
You can also spec out a change order to switch from powerwall to a SolArk or EG4 18kpv, which both handle this natively.
No solar during extended outage?
- Thread starter AaronSSH
- Start date
wattmatters
Solar Wizard
Interesting, must be different set up specs to here.
I note the document is some years old and mentions compatibility with Gateway 1, which hasn't been used for some years. Gateway 2 is the current model. I would want to check on the specs for generator use.
It also has some inconsistencies, providing micro grid frequency control specs on page 13 but then talks about 50Hz setting on page 19.
I think that documentation is out of data. This is current:
GXMnow
Solar Wizard
- Joined
- Jul 17, 2020
- Messages
- 2,718
Sorry for this fairly long post, but I have given my similar situation some thought. The issue here is called "Dark Start" and it is a problem with all AC coupled systems. In my case, I have a Schneider XW-Pro instead of a Powerwall, but it suffers a similar issue.
The best way to deal with it is to not let the batteries run down too low. Manage your loads so you don't exceed production during a grid outage.
You said you have a 23 KW solar array. And with two Powerwall2 units, you should be able to easily maintain a decent amount of power for a long time. But if the batteries do start to get below 20% remaining, turn off any non essential loads so that you don't run out completely. As long as the Powerwall is able to form the AC waveform, the Enphase microinverters should be able to push power in and charge the system when the sun comes out. But the moment the Powerwall shuts down, you lose the solar as well.
The generator is an extreme backup measure for when you have poor solar production for a long time with the grid down. Going to generator should be very rare, even in an extended grid outage.
Most generators can't tolerate any AC coupled solar. The Enphase (or any other grid tied inverter) will try to push power back into the generator's output, and that can cause damage. So when the generator is commanded to start, the AC coupled solar has to disconnect. This is not unique to the Powerwall. It is true for any AC coupled system using Grid Tied inverters in an off grid situation.
In the explanation above, it sounds like they place the generator transfer switch AFTER the Powerwall. In that setup, it is correct that it won't be able to charge from the generator power. The output of the Powerwall becomes disconnected by the transfer switch.
To make the Powerwall2 charge from the generator, the generator transfer switch would need to be before the Powerwall. And this does add a different control requirement. The control sensing to tell the generator to start needs to be changed to the battery state of charge instead of the grid input loss. If the Powerwall was after a normal backup generator, the generator would just start as soon as the grid went down. And then the Powerwall would not know the grid went down and you would be running on the generator, AND the microinverters would also still push power and could cause the generator to be damaged.
Having the physical transfer before the Powerwall, but sensing for the grid at the power in the house sort of works as it won't start if the Powerwall is keeping the lights on. But this still causes a logic issue. If the Powerwall shuts off, then the generator will be commanded to start, but then the house has power again, so the generator will see a good grid and shut back off. Oops, and this will keep repeating. So a simple generator backup power control system just won't work. It needs separate grid sensing as well as battery charge state sensing.
I looked up a Powerwall2 installation manual, and it had no mention of generator integration. I was not able to find any place where it would command a generator. It is very likely that they never built in the control routine needed to tell a generator to start based on battery state of charge. So their easy solution is placing a standard backup generator after the Powerwall. That does sort of crash Dark Start as both the Powerwall and the PV solar ends up in a dead state.
An external control setup could be built to make it work, but I Am sure it would void any system warranty from Tesla. One simple way to possibly make it work would be to wire up a pair of contactors on the output of the generator. When the generator starts making power, one contactor disconnects the Enphase grid tie inverters so that they can't back feed into the generator. The second contactor switches the grid sensing from after the Powerwall back to the grid input.
This should make it work like this....
When the grid goes down, the Powerwall(s) take over and keep the power on in the house. The Tesla power gateway is after the generator transfer switch, but the generators automatic start is seeing a good grid through a relay in the normally closed position. This shows the generator control that the "grid" is still good.
As long as the Enphase inverters keep making enough power, the system stays running on Solar charging the Powerwall(s) when the sun is up and the batteries in the Powerwall(s) keep the house powered.
But we now have a few days of storms with heavy clouds and the Powerwall(s) batteries run too low and they shut off. The power to the house does drop out. The generator control system sees the loss of power and the generator starts up. When it fires up, it powers the two relays. The grid power sensing is switched back to the grid and th Enphase inverters are disconnected. But the Generator transfer is before the Powerwall(s). They see good grid power and since they are at a low state of charge, they should begin to charge a bit from grid, actually the running generator. With this simple logic change, the generator would just stay running until the grid comes back on, But if you see the batteries have charged back up, you should be able to manually stop the generator and t will transition back to running on the batteries, and the solar can start working in another 5 minutes.
The best way to deal with it is to not let the batteries run down too low. Manage your loads so you don't exceed production during a grid outage.
You said you have a 23 KW solar array. And with two Powerwall2 units, you should be able to easily maintain a decent amount of power for a long time. But if the batteries do start to get below 20% remaining, turn off any non essential loads so that you don't run out completely. As long as the Powerwall is able to form the AC waveform, the Enphase microinverters should be able to push power in and charge the system when the sun comes out. But the moment the Powerwall shuts down, you lose the solar as well.
The generator is an extreme backup measure for when you have poor solar production for a long time with the grid down. Going to generator should be very rare, even in an extended grid outage.
Most generators can't tolerate any AC coupled solar. The Enphase (or any other grid tied inverter) will try to push power back into the generator's output, and that can cause damage. So when the generator is commanded to start, the AC coupled solar has to disconnect. This is not unique to the Powerwall. It is true for any AC coupled system using Grid Tied inverters in an off grid situation.
In the explanation above, it sounds like they place the generator transfer switch AFTER the Powerwall. In that setup, it is correct that it won't be able to charge from the generator power. The output of the Powerwall becomes disconnected by the transfer switch.
To make the Powerwall2 charge from the generator, the generator transfer switch would need to be before the Powerwall. And this does add a different control requirement. The control sensing to tell the generator to start needs to be changed to the battery state of charge instead of the grid input loss. If the Powerwall was after a normal backup generator, the generator would just start as soon as the grid went down. And then the Powerwall would not know the grid went down and you would be running on the generator, AND the microinverters would also still push power and could cause the generator to be damaged.
Having the physical transfer before the Powerwall, but sensing for the grid at the power in the house sort of works as it won't start if the Powerwall is keeping the lights on. But this still causes a logic issue. If the Powerwall shuts off, then the generator will be commanded to start, but then the house has power again, so the generator will see a good grid and shut back off. Oops, and this will keep repeating. So a simple generator backup power control system just won't work. It needs separate grid sensing as well as battery charge state sensing.
I looked up a Powerwall2 installation manual, and it had no mention of generator integration. I was not able to find any place where it would command a generator. It is very likely that they never built in the control routine needed to tell a generator to start based on battery state of charge. So their easy solution is placing a standard backup generator after the Powerwall. That does sort of crash Dark Start as both the Powerwall and the PV solar ends up in a dead state.
An external control setup could be built to make it work, but I Am sure it would void any system warranty from Tesla. One simple way to possibly make it work would be to wire up a pair of contactors on the output of the generator. When the generator starts making power, one contactor disconnects the Enphase grid tie inverters so that they can't back feed into the generator. The second contactor switches the grid sensing from after the Powerwall back to the grid input.
This should make it work like this....
When the grid goes down, the Powerwall(s) take over and keep the power on in the house. The Tesla power gateway is after the generator transfer switch, but the generators automatic start is seeing a good grid through a relay in the normally closed position. This shows the generator control that the "grid" is still good.
As long as the Enphase inverters keep making enough power, the system stays running on Solar charging the Powerwall(s) when the sun is up and the batteries in the Powerwall(s) keep the house powered.
But we now have a few days of storms with heavy clouds and the Powerwall(s) batteries run too low and they shut off. The power to the house does drop out. The generator control system sees the loss of power and the generator starts up. When it fires up, it powers the two relays. The grid power sensing is switched back to the grid and th Enphase inverters are disconnected. But the Generator transfer is before the Powerwall(s). They see good grid power and since they are at a low state of charge, they should begin to charge a bit from grid, actually the running generator. With this simple logic change, the generator would just stay running until the grid comes back on, But if you see the batteries have charged back up, you should be able to manually stop the generator and t will transition back to running on the batteries, and the solar can start working in another 5 minutes.
12VoltInstalls
life passes by too quickly to not live in freedom
No. It sounds retail.
This is why I’m my own mechanic and installer. “Everything” is usually attainable but people taking your money often are interested in completing a contract rather than giving you excellent information and verifying expectations.
Long post greatly appreciated, thank you!
There is a lot of good info here. Maybe I'm saying the same thing, but what comes to mind is that all I really need is some kind of control device that can watch the Powerwall battery level and shut it off at 10%, then turn it back on when the sun is shining. That's all I need. It wouldn't even directly have any loads flowing through it, just a simple If-This-Then-That. Unfortunately I checked IFTT.com for it just now but no Powerwall integration to IFTT.
What is not clear to me at this point is that some people here have replied to say that the Powerwall does do this automatically at 10%, but my installer and others here suggest that it can't be programmed do that. So I still don't really know. Once the power company installs my net-metering metering and I can turn the solar on, looks I am going to have to do a few trials to confirm either way and report back so that others know for sure.
So it appears that Tesla opened their API in January so in theory I could write my own code to do what I want it to do. But it appears that someone already has a SmartThings / Powerwall integration built out that works so I may be able to just use that:
darwinsden.com
Tesla Powerwall Manager app for SmartThings and Hubitat Hubs - DarwinsDen.com
Introducing the Powerwall Manager SmartApp for SmartThings and Hubitat Hubs Update 1-Jan-2023: This app is still fully operational on the Hubitat Hub platform, however due to recent changes on the SmartThings platform to eliminate the hosted Groovy application capability, this app is no longer...
darwinsden.com
GXMnow
Solar Wizard
- Joined
- Jul 17, 2020
- Messages
- 2,718
The additional problem is that you can't tell if/when you have enough solar coming in to switch the Powerwall back on. The AC coupled solar is dead, no matter how much sun there is, until the Powerwall is producing a good local grid for over 5 minutes from the remaining battery power.
My system is actually a Schneider XW-Pro, but I was in the same boat with Enphase Microinverters AC coupled to it. If the batteries ran down too low, the system shuts down with no way to self start. I tried to think up a few ways to work around that. One was to use a small solar panel. When the power from that panel hits a certain level, send the command to turn the inverter back on. Then in 5 minutes, the large solar array comes online and it starts charging again.
In the end I "cheated" I did add extra solar panels, but in my case, they directly charge the batteries. I don't think that is possible on the Powerwall2. What is the battery voltage in the Powerwall2? Maybe a charge controller could be wired into it? This is basically what the new Powerwall3 will do. It is DC coupled with a solar input into the battery.
My system is actually a Schneider XW-Pro, but I was in the same boat with Enphase Microinverters AC coupled to it. If the batteries ran down too low, the system shuts down with no way to self start. I tried to think up a few ways to work around that. One was to use a small solar panel. When the power from that panel hits a certain level, send the command to turn the inverter back on. Then in 5 minutes, the large solar array comes online and it starts charging again.
In the end I "cheated" I did add extra solar panels, but in my case, they directly charge the batteries. I don't think that is possible on the Powerwall2. What is the battery voltage in the Powerwall2? Maybe a charge controller could be wired into it? This is basically what the new Powerwall3 will do. It is DC coupled with a solar input into the battery.
wattmatters
Solar Wizard
Contact Tesla directly and escalate to level 2 support.
