Battery solutions for IQ System Controller 2
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GXMnow
Solar Wizard
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- Jul 17, 2020
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I have an older Enphase system (not quite 3 years yet) so my system is an iQ Combiner 3 and iQ7 microinverters. I have it working very successfully with a Schneider XW-Pro inverter, but I had to program a PLC to force it to do time of use energy shifting. For backup power only, it does work great with no extra equipment needed beyond the XW-Pro inverter and their Gateway. The Gateway has been replaced with the "Insight Home" box now. It seems 3 years is long for technology equipment now days.
The first question is what is your reason for adding batteries?
If you want to do time of use management and self consumption of your extra solar power, then you will most likely be better off going with the iQ batteries from Enphase. Unless you are able to program a device to manage the XW-Pro inverter, it is not happy in an AC coupled only system like this. I spent a solid year having to manually start it charging each morning. My solution, which does work great (now) is using a Triangle Research Nano-10 PLC. All up, it was about $300 in hardware, so it's not too bad. It is a bare PC board, so I had to get a case and mount it etc. It reads data from the XW-Pro inverter and is able to start it charging, and adjust the charge rate to use the extra solar that would normally be exported. Then it can just let the XW-Pro take over to back feed the battery power to the system during the peak rate time. I also added a pair of power meters. The PLC also reads those, and it can now also adjust the export from the XW to control how much better energy is exported to match the power use in the house.
If you are not comfortable doing a bit of network setup and coding in a form of Basic language, then try something else.
If all you want is backup power, the XW-Pro does work great with the Enphase iQ7 inverters, and I see no reason that the iQ8's would have a problem. The issue is the iQ System Controller 2. Since you have that device, I assume you already have the "Sunlight Backup" from Enphase. Their controller is already setup to take the iQ8 inverters off of the grid. The iQ8's then form the grid themselves, with the Controller having the required transformer to form the neutral in the typical USA home 120/240 split phase power system.
The XW-Pro (as well as any other hybrid battery inverter for the USA 120/240 system) also has a transfer relay system and it's own neutral forming device. Interfacing both systems together might be a problem. Looking at some of the data I can find on the System Controller, it could be a bit of a pain to make this work together for backup power. The "PROPER" way to do it would be to eliminate the iQ System Controller 2 unit, and essentially replace it with a battery based hybrid inverter. But that is way beyond a normal Do It Yourself kind of project.
So here is my brainstorm idea.....
Leave the complete iQ8 system alone.
Connect the Schneider XW-Pro AC1 grid input to the main panel before the iQ System Controller 2.
Program a PLC similar to what I am doing. Add a grid side power meter that can tell power direction. If your solar starts exporting power, have it command the XW-Pro to go into charge mode. Have the "Sell Mode" set to allow grid sell, and when the power meters show power coming in from the grid, have it adjust the grid sell power to zero it out.
I know the XW-Pro will do this, as that is how I had it connected to my system for a few weeks when I first got it. I did not have the PLC or power meters, so I was having to stat a charge cycle each morning, but then it would top up, and go to a fixed rate of sell current in the 4pm to 9pm peak time of use rate block. Adding the power meter(s) with the PLC commanding the charge and discharge current would make this work great for time of use shifting and self consumption. But this part alone does not give night time backup power. I think I still have some of the data from my utility when I was doing this. I finally wired my Enphase gear into the backup loads panel when I had a true grid power failure.
In this setup, the Enphase gear does not even know any of this is happening. It will just keep seeing a good grid in front of it as long as the grid is actually up. A grid outage will still shut down the input side of all this. Your sunlight backup should still work as it does now.
If you want backup power at night during the blackout, you can add a battery backup loads panel on the output of the XW-Pro, but this alone will only have the power left in the batteries. But I have an idea for that as well.
Connect a 240 volt circuit from the sunlight backup power panel to the AC2 input of the XW pro. This is commonly used for a generator. When the sun comes up, and the iQ8s start to make power, the XW-Pro will see that as a running generator, and you can command it to charge the batteries from that. It will also pass that power through to the backup loads panel after the XW-Pro inverter. When the sun goes down, the iQ8s shut down again, and the XW goes back to running the backup loads panel off of the batteries again. The only problem I see with this setup is figuring out how much charge current you can pull from the sunlight backup system. If you pull too much, it will have to shut it off. You can only take about 80% of what the solar panels are producing at that instant of time. Even a cloud passing will be a problem. I would need to think about how to work that into the system during a grid outage. This is the one place where the iQ8 doing grid forming is actually a problem. It will adjusts it's output current to keep the house voltage at 240, but it might only be putting out 3 amps, to do it, when the solar panels are making enough power to produce 15 amps. My "Dumb" iQ7s will always just push as much current as they can for all of the solar hitting them. The XW-Pro then pushes whatever the loads are not using into the batteries.
For this all to work, it will need a custom program in the PLC and about 4 current monitors. If you have the programming ability and see it as a challenge, it could be a fun project. But if you were to hire someone to do it, it will likely cost as much as just buying the Enphase batteries.
I am happy to discuss this, and can offer my coding, but this is not a simple plug and play setup.
The first question is what is your reason for adding batteries?
If you want to do time of use management and self consumption of your extra solar power, then you will most likely be better off going with the iQ batteries from Enphase. Unless you are able to program a device to manage the XW-Pro inverter, it is not happy in an AC coupled only system like this. I spent a solid year having to manually start it charging each morning. My solution, which does work great (now) is using a Triangle Research Nano-10 PLC. All up, it was about $300 in hardware, so it's not too bad. It is a bare PC board, so I had to get a case and mount it etc. It reads data from the XW-Pro inverter and is able to start it charging, and adjust the charge rate to use the extra solar that would normally be exported. Then it can just let the XW-Pro take over to back feed the battery power to the system during the peak rate time. I also added a pair of power meters. The PLC also reads those, and it can now also adjust the export from the XW to control how much better energy is exported to match the power use in the house.
If you are not comfortable doing a bit of network setup and coding in a form of Basic language, then try something else.
If all you want is backup power, the XW-Pro does work great with the Enphase iQ7 inverters, and I see no reason that the iQ8's would have a problem. The issue is the iQ System Controller 2. Since you have that device, I assume you already have the "Sunlight Backup" from Enphase. Their controller is already setup to take the iQ8 inverters off of the grid. The iQ8's then form the grid themselves, with the Controller having the required transformer to form the neutral in the typical USA home 120/240 split phase power system.
The XW-Pro (as well as any other hybrid battery inverter for the USA 120/240 system) also has a transfer relay system and it's own neutral forming device. Interfacing both systems together might be a problem. Looking at some of the data I can find on the System Controller, it could be a bit of a pain to make this work together for backup power. The "PROPER" way to do it would be to eliminate the iQ System Controller 2 unit, and essentially replace it with a battery based hybrid inverter. But that is way beyond a normal Do It Yourself kind of project.
So here is my brainstorm idea.....
Leave the complete iQ8 system alone.
Connect the Schneider XW-Pro AC1 grid input to the main panel before the iQ System Controller 2.
Program a PLC similar to what I am doing. Add a grid side power meter that can tell power direction. If your solar starts exporting power, have it command the XW-Pro to go into charge mode. Have the "Sell Mode" set to allow grid sell, and when the power meters show power coming in from the grid, have it adjust the grid sell power to zero it out.
I know the XW-Pro will do this, as that is how I had it connected to my system for a few weeks when I first got it. I did not have the PLC or power meters, so I was having to stat a charge cycle each morning, but then it would top up, and go to a fixed rate of sell current in the 4pm to 9pm peak time of use rate block. Adding the power meter(s) with the PLC commanding the charge and discharge current would make this work great for time of use shifting and self consumption. But this part alone does not give night time backup power. I think I still have some of the data from my utility when I was doing this. I finally wired my Enphase gear into the backup loads panel when I had a true grid power failure.
In this setup, the Enphase gear does not even know any of this is happening. It will just keep seeing a good grid in front of it as long as the grid is actually up. A grid outage will still shut down the input side of all this. Your sunlight backup should still work as it does now.
If you want backup power at night during the blackout, you can add a battery backup loads panel on the output of the XW-Pro, but this alone will only have the power left in the batteries. But I have an idea for that as well.
Connect a 240 volt circuit from the sunlight backup power panel to the AC2 input of the XW pro. This is commonly used for a generator. When the sun comes up, and the iQ8s start to make power, the XW-Pro will see that as a running generator, and you can command it to charge the batteries from that. It will also pass that power through to the backup loads panel after the XW-Pro inverter. When the sun goes down, the iQ8s shut down again, and the XW goes back to running the backup loads panel off of the batteries again. The only problem I see with this setup is figuring out how much charge current you can pull from the sunlight backup system. If you pull too much, it will have to shut it off. You can only take about 80% of what the solar panels are producing at that instant of time. Even a cloud passing will be a problem. I would need to think about how to work that into the system during a grid outage. This is the one place where the iQ8 doing grid forming is actually a problem. It will adjusts it's output current to keep the house voltage at 240, but it might only be putting out 3 amps, to do it, when the solar panels are making enough power to produce 15 amps. My "Dumb" iQ7s will always just push as much current as they can for all of the solar hitting them. The XW-Pro then pushes whatever the loads are not using into the batteries.
For this all to work, it will need a custom program in the PLC and about 4 current monitors. If you have the programming ability and see it as a challenge, it could be a fun project. But if you were to hire someone to do it, it will likely cost as much as just buying the Enphase batteries.
I am happy to discuss this, and can offer my coding, but this is not a simple plug and play setup.
Ellis Redding
New Member
- Joined
- Feb 23, 2022
- Messages
- 108
Hmm, that's a lot more complicated than I was hoping.
Any chance you have a drawing and / or photo?
Any chance you have a drawing and / or photo?
GXMnow
Solar Wizard
- Joined
- Jul 17, 2020
- Messages
- 2,710
What are your goals with adding the battery?
Do you need night backup for grid failure?
Or is time shifting the power more important?
Ideally, it is nice to get both, but it took me a while to make it work. But now I do know how with the Schneider inverter.
Do you need night backup for grid failure?
Or is time shifting the power more important?
Ideally, it is nice to get both, but it took me a while to make it work. But now I do know how with the Schneider inverter.
Ellis Redding
New Member
- Joined
- Feb 23, 2022
- Messages
- 108
3 Goals,
1. Utility doesn't credit kWh 1:1. They give $0.04 / kWh, so would prefer to store and consumer anything I can rather than give it back to the grid.
2. Would also like to have a more stable Grid-Down ability.
3. Haven't run the calc, but guessing the Enphase battery / batteries I'd need to accomplish goal 2 would cost a lot more than a decent hybrid with LiFePos, so a little financial there too.
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