Kind of hard to do regular watering on batteries inside something sealed with silicone unless you plan on replacing the silicone each time to maintain integrity of it's sealing... but sounds like you are aware of the risks... rule number one of FLA/Inverter installation is NEVER mount FLA under electronic equipment (of any type) but it's your equip, we can only share our thoughts... being in the middle of Schneider support hell at the moment I know how hard it is go get anything fixed, hopefully it never becomes an issue for you, if it does, tip... learn Punjabi. Make sure you check for gas exit during an eq phase at least... I won't touch if you're risking your warranty with them right there.. ouch.
Schneider system design wasteland......no one knows anything.....
- Thread starter pvdude
- Start date
Eh.. You need a battery ?
GXMnow
Solar Wizard
- Joined
- Jul 17, 2020
- Messages
- 2,698
pvdude,
Have you done a reasonable energy audit of how much energy you really use while the sun is up and while the sun is down?
My system is using a single XW-Pro battery inverter, but all of my solar is currently AC coupled from Enphase microinverters. I am also grid tied, but I have been doing the math to figure out what I would need to do to eliminate using grid power unless something goes wrong.
The XW-Pro is a beast of an inverter, and it will support cranking out 6,800 watts all day long. That is a true continuous rating. The surge rating is 12,000 watts. To hit that urge, your battery bank will need to supply about 250 amps into the inverter. At 6,800 watts, it is still pulling about 140 amps. In my case, a single XW-Pro could run everything in my house with only one exception, my central air conditioner compressor has a 105 amp starting surge. So I left that on the main grid panel. With a soft start unit, it might be able to run off the inverter, but for the few times my grid has gone down, I can deal without having air conditioning.
If you truly need more than the 6,800 watts continuous, then two or even 3 XW-Pro inverters may be needed, but that is a huge amount of power.
The next thing to look at is the total watt hours used in a day. And then splitting it up to what is used when the sun is up, and when the sun is down. With all DC coupled solar, all of your AC power is going in and back out of the batteries, all of the time. The battery is a buffer. In reality, yes, the inverter is using some of the solar that does not make it into the battery, but because of how the inverter works to make a true since wave, it is pulling the power in cycles making the top half, and then the bottom half of the sine wave. At zero crossing, the solar is charging the battery, at peak, the inverter is pulling a bit from the battery. At 60hz, there are 120 current pulses per second.
In my case I am completely AC coupled. When the sun is up, my Enphase microinverters are powering all the loads directly. I have the charge rate set so that the XW-Pro is only using power that I am not using in my home. This power would have been exported out to the grid. I have it charge at just 25 amps or so, over 8 hours while the sun is shining. I know, that is only 200 amp hours. I do want to step this up a bit, but I need to add more solar. I only have 4,800 watts of panels, and 3,900 watts of solar grid tie inverter output. I am 25% over paneled to the inverters. They only hit clip on very sunny but cool days. I produce up to 31 KWHs a day in ideal conditions, my average is about 23 KWHs a day. When the sun goes down, I run my home off of the battery bank, and it supplies most of my needs. But I do fall short when I am running the Central air conditioning.
After much thinking and research, I have come to the conclusion that having both DC and AC coupling makes the most sense.
My existing microinverters supply more than the power I need while the sun is up. but it is a pain to regulate how much to push into the batteries. And the fact that the XW-Pro software has no way of switching into charge mode on it's own. I really feel this is a bad software issue, but that is another thread. So my plan is to add a DC solar array and charge controller that can supply the power I use at night, when the sun is down. I want to add 2,000 to 4,000 watts of DC solar panels. The XW will basically sit in standby from sunrise to sunset. The DC charge controller will harvest all it can and charge the battery bank. If the batteries do become full, it will throw away any additional production, nothing I can do about that, except maybe a load dump like an electric water heater. As the sun falls, the XW-Pro will come online and power my home off the stored power in the batteries from the DC solar.
It really becomes 2 separate systems. AC solar provide all the power during the day, and the DC solar provides all of the power at night. If you do need some crazy power at say 2 pm, to run a welder, then the XW-Pro could go into "Grid Support, and add it's up to 6,800 watts to the 3,000 watts that are coming from the Enphase microinverters. And the DC solar, will be providing some of the power, so the batteries will not be discharging very fast. When the sun is down, you are back to being limited to just the XW-Pro output. But in my case, being "Grid Tied", If I need more power than my inverters, it will just pull from the grid, and if I am producing more than I need, it can sell out to the grid. As cool as it would be to go fully off grid, having the grid there is like having a massive extra battery bank available when things are not balanced. Off grid, you really need to balance your production and load much closer.
As I have been thinking about this for nearly a year now, since I put my XW-Pro into service, I truly believe the combination of AC and DC coupling is the best way to go. For both on and off grid systems. Direct Solar to AC inverters, either string or microinverters are still the most efficient way to get AC power while the sun is shining. But they do not store extra power very well. But as I learned with my latest grid power failure, the XW-Pro does work great when off grid, and took all of my extra solar and was able to push that into the batteries, but at about 85% efficiency. That is way better than just throwing it away though. But having to convert DC from the solar to AC, then back to DC to charge the batteries, and then back to AC to run loads... That is a lot of conversions. Not take DC solar.... When the sun is up, you are taking the solar array high voltage, stepping it down, and regulating it to charge the battery bank, and the inverter has to work off this low battery voltage and step it back up and form an AC sine wave. That is not the best efficiency either. But when you can time shift the DC power from when the sun is shining to when the sun is down, then it becomes the best way to get the power at night. Due to roof space limits, I may actually take a few of my AC panels, and remove the microinverters and use them as DC panels. I typically use a little more power when the sun is down compared to when it is up. I have 4,800 watts of AC panels now, but only have room for about 3,000 watts more. Since I want more power at night, I might benefit from only 3,600 watts of AC panel, and 4,200 watts of DC panel. but this is my use case, yours may vary. Do some energy use calculations and see when you are using the power, and when the solar is producing. I firmly believe, that combining the right balance of AC and DC solar will produce the best system. And this is true for both on and off grid.
As for the original post here, you certainly can add more DC charge controllers and solar panels, but once you hit the maximum charge rate of the batteries, you have a problem.
Have you done a reasonable energy audit of how much energy you really use while the sun is up and while the sun is down?
My system is using a single XW-Pro battery inverter, but all of my solar is currently AC coupled from Enphase microinverters. I am also grid tied, but I have been doing the math to figure out what I would need to do to eliminate using grid power unless something goes wrong.
The XW-Pro is a beast of an inverter, and it will support cranking out 6,800 watts all day long. That is a true continuous rating. The surge rating is 12,000 watts. To hit that urge, your battery bank will need to supply about 250 amps into the inverter. At 6,800 watts, it is still pulling about 140 amps. In my case, a single XW-Pro could run everything in my house with only one exception, my central air conditioner compressor has a 105 amp starting surge. So I left that on the main grid panel. With a soft start unit, it might be able to run off the inverter, but for the few times my grid has gone down, I can deal without having air conditioning.
If you truly need more than the 6,800 watts continuous, then two or even 3 XW-Pro inverters may be needed, but that is a huge amount of power.
The next thing to look at is the total watt hours used in a day. And then splitting it up to what is used when the sun is up, and when the sun is down. With all DC coupled solar, all of your AC power is going in and back out of the batteries, all of the time. The battery is a buffer. In reality, yes, the inverter is using some of the solar that does not make it into the battery, but because of how the inverter works to make a true since wave, it is pulling the power in cycles making the top half, and then the bottom half of the sine wave. At zero crossing, the solar is charging the battery, at peak, the inverter is pulling a bit from the battery. At 60hz, there are 120 current pulses per second.
In my case I am completely AC coupled. When the sun is up, my Enphase microinverters are powering all the loads directly. I have the charge rate set so that the XW-Pro is only using power that I am not using in my home. This power would have been exported out to the grid. I have it charge at just 25 amps or so, over 8 hours while the sun is shining. I know, that is only 200 amp hours. I do want to step this up a bit, but I need to add more solar. I only have 4,800 watts of panels, and 3,900 watts of solar grid tie inverter output. I am 25% over paneled to the inverters. They only hit clip on very sunny but cool days. I produce up to 31 KWHs a day in ideal conditions, my average is about 23 KWHs a day. When the sun goes down, I run my home off of the battery bank, and it supplies most of my needs. But I do fall short when I am running the Central air conditioning.
After much thinking and research, I have come to the conclusion that having both DC and AC coupling makes the most sense.
My existing microinverters supply more than the power I need while the sun is up. but it is a pain to regulate how much to push into the batteries. And the fact that the XW-Pro software has no way of switching into charge mode on it's own. I really feel this is a bad software issue, but that is another thread. So my plan is to add a DC solar array and charge controller that can supply the power I use at night, when the sun is down. I want to add 2,000 to 4,000 watts of DC solar panels. The XW will basically sit in standby from sunrise to sunset. The DC charge controller will harvest all it can and charge the battery bank. If the batteries do become full, it will throw away any additional production, nothing I can do about that, except maybe a load dump like an electric water heater. As the sun falls, the XW-Pro will come online and power my home off the stored power in the batteries from the DC solar.
It really becomes 2 separate systems. AC solar provide all the power during the day, and the DC solar provides all of the power at night. If you do need some crazy power at say 2 pm, to run a welder, then the XW-Pro could go into "Grid Support, and add it's up to 6,800 watts to the 3,000 watts that are coming from the Enphase microinverters. And the DC solar, will be providing some of the power, so the batteries will not be discharging very fast. When the sun is down, you are back to being limited to just the XW-Pro output. But in my case, being "Grid Tied", If I need more power than my inverters, it will just pull from the grid, and if I am producing more than I need, it can sell out to the grid. As cool as it would be to go fully off grid, having the grid there is like having a massive extra battery bank available when things are not balanced. Off grid, you really need to balance your production and load much closer.
As I have been thinking about this for nearly a year now, since I put my XW-Pro into service, I truly believe the combination of AC and DC coupling is the best way to go. For both on and off grid systems. Direct Solar to AC inverters, either string or microinverters are still the most efficient way to get AC power while the sun is shining. But they do not store extra power very well. But as I learned with my latest grid power failure, the XW-Pro does work great when off grid, and took all of my extra solar and was able to push that into the batteries, but at about 85% efficiency. That is way better than just throwing it away though. But having to convert DC from the solar to AC, then back to DC to charge the batteries, and then back to AC to run loads... That is a lot of conversions. Not take DC solar.... When the sun is up, you are taking the solar array high voltage, stepping it down, and regulating it to charge the battery bank, and the inverter has to work off this low battery voltage and step it back up and form an AC sine wave. That is not the best efficiency either. But when you can time shift the DC power from when the sun is shining to when the sun is down, then it becomes the best way to get the power at night. Due to roof space limits, I may actually take a few of my AC panels, and remove the microinverters and use them as DC panels. I typically use a little more power when the sun is down compared to when it is up. I have 4,800 watts of AC panels now, but only have room for about 3,000 watts more. Since I want more power at night, I might benefit from only 3,600 watts of AC panel, and 4,200 watts of DC panel. but this is my use case, yours may vary. Do some energy use calculations and see when you are using the power, and when the solar is producing. I firmly believe, that combining the right balance of AC and DC solar will produce the best system. And this is true for both on and off grid.
As for the original post here, you certainly can add more DC charge controllers and solar panels, but once you hit the maximum charge rate of the batteries, you have a problem.
Thanks very much for the thought provoking discussion!
With the amount of PV I have now, and the 100A 600vdc Conext charge controller, I am at the limit for charging 445Ah of FLA.
I was considering more PV DC coupled just to compensate for the PV losses due the clouds here in the wet season.
My system seems to behave a little different, with respect to how the DC coupled works.
Running the 1.11 firmware on the XW Pro, and the updated firmware on the MPPT CC, the PV energy bypasses the batteries and goes directly to the load.
The only time the batteries are called is when there is not enough PV to handle the load, in which case the inverter takes PV energy first, and supplements from the batteries, until the PV energy returns to a level to fully power the load.
This is off-grid, and primary use is to run the well pump and workshop AC & small refrigerator.
So in the hot months here (9-10 months), the load is about 1400 watts from the workshop AC and refrigerator.
Jumps to 3100 watts when the well pump comes on.
(Well pump does not cycle that much, except on laundry day)
The house is not normally connected to the solar, except when there is a grid outage.
I am investigating more power, so we could possibly run the house as well as the separate workshop, on cases where the grid is down for an extended period of time.
Using the 21kw Diesel genset is an absolutely last resort, trying to avoid that.
We would like to run the heat pump from the solar, but the 132 LRA is a problem!
Hyperengineering tech support said the soft start equipment I have (not installed yet) will reduce the LRA to about 9kw!
Heat pump running power consumption is about 2-3kw.
So with every non-critical load in the house switched off, about 800-1200 watts, total load from house (lighting, refrigerator, fan).
The 445Ah FLA is plenty to power the house all night @ that level of consumption.
When the heat pump is running, 3-4kw. (Can’t run that on batteries for very long)
Heat pump plus well pump with a 30-45 second spike to 5-6kw when the well pump comes on.
If I add some AC coupled, leave the DC as is, that might use the batteries less, if I am understanding the basic AC coupled principle.
Then we could actually run the heat pump when there is adequate Sun, rather than start the generator.
The PV max Sun growth area in the yard is 200ft from the workshop, where the solar electronics is installed.
Looks like a micro inverter puts out AC, so there would be cabling energy loss to factor in, guessing there are micro inverters w/ AC output of 240?
With the amount of PV I have now, and the 100A 600vdc Conext charge controller, I am at the limit for charging 445Ah of FLA.
I was considering more PV DC coupled just to compensate for the PV losses due the clouds here in the wet season.
My system seems to behave a little different, with respect to how the DC coupled works.
Running the 1.11 firmware on the XW Pro, and the updated firmware on the MPPT CC, the PV energy bypasses the batteries and goes directly to the load.
The only time the batteries are called is when there is not enough PV to handle the load, in which case the inverter takes PV energy first, and supplements from the batteries, until the PV energy returns to a level to fully power the load.
This is off-grid, and primary use is to run the well pump and workshop AC & small refrigerator.
So in the hot months here (9-10 months), the load is about 1400 watts from the workshop AC and refrigerator.
Jumps to 3100 watts when the well pump comes on.
(Well pump does not cycle that much, except on laundry day)
The house is not normally connected to the solar, except when there is a grid outage.
I am investigating more power, so we could possibly run the house as well as the separate workshop, on cases where the grid is down for an extended period of time.
Using the 21kw Diesel genset is an absolutely last resort, trying to avoid that.
We would like to run the heat pump from the solar, but the 132 LRA is a problem!
Hyperengineering tech support said the soft start equipment I have (not installed yet) will reduce the LRA to about 9kw!
Heat pump running power consumption is about 2-3kw.
So with every non-critical load in the house switched off, about 800-1200 watts, total load from house (lighting, refrigerator, fan).
The 445Ah FLA is plenty to power the house all night @ that level of consumption.
When the heat pump is running, 3-4kw. (Can’t run that on batteries for very long)
Heat pump plus well pump with a 30-45 second spike to 5-6kw when the well pump comes on.
If I add some AC coupled, leave the DC as is, that might use the batteries less, if I am understanding the basic AC coupled principle.
Then we could actually run the heat pump when there is adequate Sun, rather than start the generator.
The PV max Sun growth area in the yard is 200ft from the workshop, where the solar electronics is installed.
Looks like a micro inverter puts out AC, so there would be cabling energy loss to factor in, guessing there are micro inverters w/ AC output of 240?
GXMnow
Solar Wizard
- Joined
- Jul 17, 2020
- Messages
- 2,698
You are correct.
When DC coupling, yes, the solar is sort of going straight from the charge controller to the inverter, but, the battery must be there as a buffer because of the power not being constant. So if you do average over a minute, it does look like all of the power came straight from solar when the sun is shining. But you do still have some current going in and back out 120 times per second.
With the Microinverters, that buffering is just done in a capacitor in the inverter. The Enphase iQ7's are rated at something like 97% efficiency from solar DC input to AC output. They really are quite amazing. They do output 240 volts, AC at about 1 amp per inverter, depending on which model. Mine are the lowest rated at 240 watts and only 60 cell panels. They are a very good match for my 300 watt mono panels here in So Cal. They also have the Plus, the X, and A versions now for larger solar panels with 60, 66, 72, or even 96 cells.
My two panel strings use the standard #12 awg Enphase trunk cable with only 8 inverters on each, so just 8 amps, so not much voltage drop there. Once the two strings are in my attic, they splice to a single pair of #10 awg wire for a 60 foot run to my garage where they tie into my system. The drop at 16 amps it quite small. If the run was 1,000 feet (300 meters) I would probably step it up to #8 or even #6 cable to minimize losses. 240 volt is halfway between a 400-600 volt string system, and the under 100 volt DC systems. The AC is also far safer if there is a break as it is much less likely to arc up and start a fire.
You do have a limitation with your system due to the charge current of the flooded lead acid batteries. Since you are off grid, the XW-Pro will still try to push any excess AC coupled solar power into the batteries. So this will still be your system limit. During my last power failure, so I was running off grid, I did leave the XW-Pro set to only an 18% maximum charge rate. So it was trying to limit to just 23 amps. I totally forgot I left it that low, but that is all I need while on grid to top up my batteries in 8 hours. But since I was running off grid, I also shut off a lot of loads that were not needed to be easy on the system, I had no idea the power was going to be out. When the sun got close to solar noon, my solar output was exceeding the house loads by nearly 2,000 watts. The Enphase iQ7 inverters are still trying to pull maximum power and push it to what it thinks is the grid. The XW-Pro is taking any power above what the house is drawing, and is pushing it to the batteries. 2,000 watts / 50 volts = 40 amps. That is not a problem for my batteries, and I should have had it set to use that, but it was trying to limit to 23 amps, so this is what it did. It shifted the AC frequency up from our normal 60 Hz to nearly 62 Hz. In a perfect world, the iQ7 inverters would lower their output smoothly, but it either did not drop enough, or fast enough, so the frequency shifted a little further, and 5 of my iQ7 inverters saw it as an unstable grid and they stopped producing power. That caused the charge current to drop to a safe level, so the XW-Pro started ramping the frequency back down to the normal 60 Hz. At some point they saw the power was goo and they went back online. I can see that this repeated 4 times exactly 10 minutes apart. The charge current never exceeded the desired setting, and it still managed to keep charging and supplying all the power the house was using. So I am confident you could use this feature to protect your flooded batteries from damage.
So by the book, you can feed up to about 6,500 watts of AC solar back into the output side of the XW-Pro inverter and it will be able to form a stable grid and keep everything working. In theory, you could then pull 6,800 watts from the XW- Pro, and another 6,500 watts from the solar inverters for a max total of 13,300 watts coming out of the backup loads panel. Of course, if a cloud goes over, the load would all shift onto the XW-Pro. If it is less than 12,000 watts for 30 seconds, it will take it.
As much as I am annoyed at the Schneider (Xantrex) XW-Pro software when it is on grid, I do have to say it works amazingly well when it is off grid. In AC coupled only, it seamlessly transitioned from AC charging from grid to powering my backup panel when the grid failed, it ran on battery until the sun cam up and started makin power on the solar. The AC solar took more and more of the load as the sun rose, and the XW-Pro went from powering loads to absorbing extra power and pushing it into the batteries. When a could went over, it never missed a beat. When the solar output fell, the XW-Pro just ramped up and powered the difference, and when the cloud cleared, it went right back to charging again.
It is just a shame that once the grid is on, some of the software just goes stupid.
When DC coupling, yes, the solar is sort of going straight from the charge controller to the inverter, but, the battery must be there as a buffer because of the power not being constant. So if you do average over a minute, it does look like all of the power came straight from solar when the sun is shining. But you do still have some current going in and back out 120 times per second.
With the Microinverters, that buffering is just done in a capacitor in the inverter. The Enphase iQ7's are rated at something like 97% efficiency from solar DC input to AC output. They really are quite amazing. They do output 240 volts, AC at about 1 amp per inverter, depending on which model. Mine are the lowest rated at 240 watts and only 60 cell panels. They are a very good match for my 300 watt mono panels here in So Cal. They also have the Plus, the X, and A versions now for larger solar panels with 60, 66, 72, or even 96 cells.
My two panel strings use the standard #12 awg Enphase trunk cable with only 8 inverters on each, so just 8 amps, so not much voltage drop there. Once the two strings are in my attic, they splice to a single pair of #10 awg wire for a 60 foot run to my garage where they tie into my system. The drop at 16 amps it quite small. If the run was 1,000 feet (300 meters) I would probably step it up to #8 or even #6 cable to minimize losses. 240 volt is halfway between a 400-600 volt string system, and the under 100 volt DC systems. The AC is also far safer if there is a break as it is much less likely to arc up and start a fire.
You do have a limitation with your system due to the charge current of the flooded lead acid batteries. Since you are off grid, the XW-Pro will still try to push any excess AC coupled solar power into the batteries. So this will still be your system limit. During my last power failure, so I was running off grid, I did leave the XW-Pro set to only an 18% maximum charge rate. So it was trying to limit to just 23 amps. I totally forgot I left it that low, but that is all I need while on grid to top up my batteries in 8 hours. But since I was running off grid, I also shut off a lot of loads that were not needed to be easy on the system, I had no idea the power was going to be out. When the sun got close to solar noon, my solar output was exceeding the house loads by nearly 2,000 watts. The Enphase iQ7 inverters are still trying to pull maximum power and push it to what it thinks is the grid. The XW-Pro is taking any power above what the house is drawing, and is pushing it to the batteries. 2,000 watts / 50 volts = 40 amps. That is not a problem for my batteries, and I should have had it set to use that, but it was trying to limit to 23 amps, so this is what it did. It shifted the AC frequency up from our normal 60 Hz to nearly 62 Hz. In a perfect world, the iQ7 inverters would lower their output smoothly, but it either did not drop enough, or fast enough, so the frequency shifted a little further, and 5 of my iQ7 inverters saw it as an unstable grid and they stopped producing power. That caused the charge current to drop to a safe level, so the XW-Pro started ramping the frequency back down to the normal 60 Hz. At some point they saw the power was goo and they went back online. I can see that this repeated 4 times exactly 10 minutes apart. The charge current never exceeded the desired setting, and it still managed to keep charging and supplying all the power the house was using. So I am confident you could use this feature to protect your flooded batteries from damage.
So by the book, you can feed up to about 6,500 watts of AC solar back into the output side of the XW-Pro inverter and it will be able to form a stable grid and keep everything working. In theory, you could then pull 6,800 watts from the XW- Pro, and another 6,500 watts from the solar inverters for a max total of 13,300 watts coming out of the backup loads panel. Of course, if a cloud goes over, the load would all shift onto the XW-Pro. If it is less than 12,000 watts for 30 seconds, it will take it.
As much as I am annoyed at the Schneider (Xantrex) XW-Pro software when it is on grid, I do have to say it works amazingly well when it is off grid. In AC coupled only, it seamlessly transitioned from AC charging from grid to powering my backup panel when the grid failed, it ran on battery until the sun cam up and started makin power on the solar. The AC solar took more and more of the load as the sun rose, and the XW-Pro went from powering loads to absorbing extra power and pushing it into the batteries. When a could went over, it never missed a beat. When the solar output fell, the XW-Pro just ramped up and powered the difference, and when the cloud cleared, it went right back to charging again.
It is just a shame that once the grid is on, some of the software just goes stupid.
400bird
Solar Wizard
I realize you might be well past this, but I forgot I meant to check my MiniPDP.
I've got cut outs for 2 charge controller breakers.
I only have the battery connection breaker, no charge controllers yet.
You should be able to connect a second charge controller inside. There are plenty of open locations on the bus bars.
I’ve been learning about AC Coupled technology, and probably am not going to make any changes in the DC coupled part.
The DC coupled array energizing the Schneider 100A 600VDC CC lets it output almost 100A, which is more than the FLA’s want, so I’m going to leave that part alone.
Looks like the XW Pro will be happy to have some AC coupled PV adding amps to the AC output.
I can fit 8 of these on the roof of the shed where the Schneider equipment is installed.
A week ago, I sent an EM to Enphase, inquiring about the panels and related installation HW.
Made a similar request to a vendor of the equipment.
No responses yet.
No hurry, it it WAY to hot here to do a roof project, possibly December - February for this project.
The DC coupled array energizing the Schneider 100A 600VDC CC lets it output almost 100A, which is more than the FLA’s want, so I’m going to leave that part alone.
Looks like the XW Pro will be happy to have some AC coupled PV adding amps to the AC output.
I can fit 8 of these on the roof of the shed where the Schneider equipment is installed.
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Made a similar request to a vendor of the equipment.
No responses yet.
No hurry, it it WAY to hot here to do a roof project, possibly December - February for this project.
400bird
Solar Wizard
Yeah, if your heavy loads are during the sunlight hours, AC coupled PV can help unload the DC side and XW.
If you don't get responses on your current inquiries: I've ordered from Renvu.com. They were responsive to questions. I don't know you're location, but it worked well for me as I could pick up the order.
If alte or real goods solar has those available, they are also super responsive to a phone call.
Renvu lists those panels for less than your link, but have a minimum order of 10
If you don't get responses on your current inquiries: I've ordered from Renvu.com. They were responsive to questions. I don't know you're location, but it worked well for me as I could pick up the order.
If alte or real goods solar has those available, they are also super responsive to a phone call.
Renvu lists those panels for less than your link, but have a minimum order of 10
GVSolar
Solar Enthusiast
- Joined
- Jan 6, 2020
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FWIW I am AC & DC coupled off-grid using Schneider and Enphase equipment (AC coupled with Enphase for over a year - DC coupled with Schneider gear since 2015). My current system: Conext SW4024, MPPT 60-150 SCC (2), 3kw Renesola panels, Enphase M-215s (first generation), 3kw REC panels. Works flawlessly - frequency shift starts up/shuts down the microinverters according to my programmed battery charging specs within seconds. Because I have the old school Enphase micros, it is on/off only - no proportional output. Someday, I might replace them with the new generation M215s (but, if it ain't broke...) On a sunny day, I will routinely charge my car, run the AC, do laundry, refrigeration, etc all at the same time. The AC couple has doubled my available power - without replacing my inverter.
I suspect the "not supported for off grid systems" is a legal/sales cover - as there are some design complexities - chief among them the requirement that your battery bank be of sufficient size/headroom to accept the full output of the micros - and the need for careful routing of any AC generator input. You may want to consult with another vendor - maybe Northern Arizona Wind & Solar - or AltE. A little more research and you may find it is quite common off-grid.
Enphase and Schneider both have technical papers on some of the AC couple requirements. (see below for examples)
BTW, I have been off-grid 30 years - it gets easier all the time - and as @GXMnow said, an AC/DC coupled system can be very powerful and effective. Best.
Thanks very much, it seemed odd that the vendor would decline AC coupling off grid w/ Enphase.
I have read the documents you attached, and while I don’t fully understand all of it (yet), the one
important detail I previously missed is the bi-directional current flow through the XW Pro inverter.
It did not make sense to me that attaching 240vac micro-inverter output to the XW Pro AC out could result in current flowing to the batteries, “backwards” through the 6848 inverter.
OK, that seems to be how it works.
The Enphase “Technical brief” was very helpful.
I need some way to prevent the FLA batteries from overcharging.
Rolls told me to limit the DC amps from the charger to about 80A.
The Schneider MPPT 100A-600V charge controller has been configured so as to limit the charging, as I have seen it put 95A into the batteries.
In practice, there is almost no solar condition that causes such a large current output from the CC.
As this is off grid, the charging function in the XW Pro inverter is turned off.
The MPPT CC is the only charging source for the batteries at this time.
My Diesel genset produces too much current for the inverter relay , so the genset is not connected to the inverter.
I use switchgear to connect the genset to the AC loads directly, when necessary.
Thus, the generator is not part of the solar electrical systems in any way.
If I add Enphase AC coupled micro-inverters, I really only want them to support the AC loads, and not interact w/ the batteries at all.
I don’t know if having the charging function disabled in the inverter will prevent the Enphase micro-inverters from charging the batteries.
Or, as the document suggests, a disconnect switch could be used.
I don’t want to have anything that requires manual intervention, if possible, as the building with the equipment is far from the house, and I am getting too senile to remember to do things like “go and operate the switch”.
I don’t understand how the inverter uses frequency shifting to “inform” the Enphase micro-inverters to curtail output.
Seems like the AC loads would not like seeing the variation from 60.0Hz, but I’m sure they already thought of that, I just don’t get it yet…….
I have read the documents you attached, and while I don’t fully understand all of it (yet), the one
important detail I previously missed is the bi-directional current flow through the XW Pro inverter.
It did not make sense to me that attaching 240vac micro-inverter output to the XW Pro AC out could result in current flowing to the batteries, “backwards” through the 6848 inverter.
OK, that seems to be how it works.
The Enphase “Technical brief” was very helpful.
I need some way to prevent the FLA batteries from overcharging.
Rolls told me to limit the DC amps from the charger to about 80A.
The Schneider MPPT 100A-600V charge controller has been configured so as to limit the charging, as I have seen it put 95A into the batteries.
In practice, there is almost no solar condition that causes such a large current output from the CC.
As this is off grid, the charging function in the XW Pro inverter is turned off.
The MPPT CC is the only charging source for the batteries at this time.
My Diesel genset produces too much current for the inverter relay , so the genset is not connected to the inverter.
I use switchgear to connect the genset to the AC loads directly, when necessary.
Thus, the generator is not part of the solar electrical systems in any way.
If I add Enphase AC coupled micro-inverters, I really only want them to support the AC loads, and not interact w/ the batteries at all.
I don’t know if having the charging function disabled in the inverter will prevent the Enphase micro-inverters from charging the batteries.
Or, as the document suggests, a disconnect switch could be used.
I don’t want to have anything that requires manual intervention, if possible, as the building with the equipment is far from the house, and I am getting too senile to remember to do things like “go and operate the switch”.
I don’t understand how the inverter uses frequency shifting to “inform” the Enphase micro-inverters to curtail output.
Seems like the AC loads would not like seeing the variation from 60.0Hz, but I’m sure they already thought of that, I just don’t get it yet…….
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400bird
Solar Wizard
Yeah, I'd check with Alte or some other vendor if you want their opinion.
As far as not wanting to charge from the AC coupled side. I don't think it is possible. When off grid that current has to go somewhere. You can set the limit low and the Schneider will frequency shift to limit that current.
But, why? If your DC is only changing at 60 amps and you've got an extra 15 that isn't being used from the AC coupled side. Why would you waste that?
As far as the frequency shift, it's minor. I believe it moves to 62-63 hz and that's enough to cause full shut down of the microinverters depending on the profile chosen.
Your clocks might gain a few seconds and motors spin slightly faster. But, we're not talking 90hz
As far as not wanting to charge from the AC coupled side. I don't think it is possible. When off grid that current has to go somewhere. You can set the limit low and the Schneider will frequency shift to limit that current.
But, why? If your DC is only changing at 60 amps and you've got an extra 15 that isn't being used from the AC coupled side. Why would you waste that?
As far as the frequency shift, it's minor. I believe it moves to 62-63 hz and that's enough to cause full shut down of the microinverters depending on the profile chosen.
Your clocks might gain a few seconds and motors spin slightly faster. But, we're not talking 90hz
400bird
Solar Wizard
Also, why not run the generator though the XW? It can put out more than 60 amps, but so can the grid. Do you have enough loads to exceed the 60 amp rating on the transfer relays?
Hedges
I See Electromagnetic Fields!
- Joined
- Mar 28, 2020
- Messages
- 20,505
Probably XW can be programmed to not let more than 60A or whatever come from grid/generator. When it senses current going too high, it can invert from batteries to supply the extra. If still too high, disconnect. That's what Sunny Island does.
Some PV inverters including newer Enphase models implement frequency-watts. For instance, 100% of power output up to 61 Hz, ramped down to 0% at 62 Hz. Those which don't implement simply disconnect for over-frequency at 60.5 Hz. Frequency drops back down and after 5 minutes they reconnect at full power. Battery cycles up and down, not a very clean implementation.
Most appliances won't be adversely affected by frequency variations of a few Hz.
XW should manage power from battery to AC, and from AC (microinverters) to battery, hopefully also considering DC coupled SCC which also charge batteries.
You can't just have microinverters power AC loads because they aren't grid-forming, don't produce a regulated sine-wave voltage. Coupled with either Enphase battery microinverters or XW, should work fine. But you want frequency-watts function in the microinverters.
Some PV inverters including newer Enphase models implement frequency-watts. For instance, 100% of power output up to 61 Hz, ramped down to 0% at 62 Hz. Those which don't implement simply disconnect for over-frequency at 60.5 Hz. Frequency drops back down and after 5 minutes they reconnect at full power. Battery cycles up and down, not a very clean implementation.
Most appliances won't be adversely affected by frequency variations of a few Hz.
XW should manage power from battery to AC, and from AC (microinverters) to battery, hopefully also considering DC coupled SCC which also charge batteries.
You can't just have microinverters power AC loads because they aren't grid-forming, don't produce a regulated sine-wave voltage. Coupled with either Enphase battery microinverters or XW, should work fine. But you want frequency-watts function in the microinverters.
MichaelK
Solar Wizard
Actually, the default setting for DC charging on the XW is 140A. The AC out and AC in settings defaults are 60A. I found out the default setting was so high after the inverter would stall my generator when I first tried generator charging.
The annoying thing though about changing the settings is that it's based on a percentage of the 140A. So, if I want to charge my battery bank at 50A, I need to set the inverter to charge at 36% (50/140 = 0357).
GXMnow
Solar Wizard
- Joined
- Jul 17, 2020
- Messages
- 2,698
With the Enphase iQ7 inverters, and the Envoy, you could install the consumption CT's Between the output of the XW and the loads sub panel, and set the Enphase system for zero export. The iQ inverters will supply as much as they can pull from the sun to supply the loads after the CT's, but once the current from solar exceeds the loads, the CT's will see the current drop to zero and start to export, at that moment, the Envoy will tell the iQ inverters to reduce output. It happens very fast, and does not need to frequency shift to work as it sends data over the powerline to the inverters. There is a video on the Enphase site demonstrating this function. It is meant for places like Hawaii that do not allow power export. But it won't know the differnce between your XW and the grid.
