Hey guys, I have a 17kw solar system with two solar edge hd inverters. I also have a 20 kw generator installed onsite that automatically will start when the grid goes down. I was looking into adding batteries to my setup as the net metering policy in my area is not great. I would like the ability to charge the batteries during the day and use the batteries at night. (Basically make the home self-powered) When the grid goes down I would like the solar and batteries to remain active and when the batteries reach a low state of charge the generator will kick on. Is this kind of setup achievable? Thanks!!
AC-Coupled Grid Tie System
- Thread starter CyberMatt
- Start date
Don’t know anything about Solar Edge inverter, but that is achievable. That works with a Sol-Ark. Does your utility have Time of Day rates? Sometimes if you are not producing enough to charge batteries from PV (cloudy days, etc.). If they offer a low rate at night, you can use that to charge batteries.
No time of use just a fixed 0.5cent per kwh which is about half our electricity price
Sorry $0.05 per kwh
That is too cheap to bother with batteries, unless you just want independence.
Are you in the USA?
ncsolarelectric
Engineering Support CEO
He means, he is paying $0.10/kWh, but the utility only pays him $0.05/kWh. That's how most of the coops are here in the Southeast. Yes, you need a battery to keep the energy produced during the day to use it at night, to maximize the ROI (kind of). Batteries are expensive, it takes many years to get an ROI from even $0.10/kWh, but it helps lower the monthly bill if you can afford it.
The Enphase IQ Battery works this way, but it's very expensive and they won't like it being added to a SolarEdge system. That would probably void the warranty.
I am working on an experimental hybrid, attempting to use all UL Listed components, to make a system that can do what you need, but doesn't run off-grid so it doesn't require an expensive transfer switch. It just charges during the day and runs in parallel to offset nighttime usage. See attached. I get my battery by next weekend to test it. Then I can see if I can get it permitted.
What it needs is a PLC to control the charge and discharge timing, and battery levels.
The Enphase IQ Battery works this way, but it's very expensive and they won't like it being added to a SolarEdge system. That would probably void the warranty.
I am working on an experimental hybrid, attempting to use all UL Listed components, to make a system that can do what you need, but doesn't run off-grid so it doesn't require an expensive transfer switch. It just charges during the day and runs in parallel to offset nighttime usage. See attached. I get my battery by next weekend to test it. Then I can see if I can get it permitted.
What it needs is a PLC to control the charge and discharge timing, and battery levels.
Last edited:
Hedges
I See Electromagnetic Fields!
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Some people replace Solar Edge with StorEdge, but then you need an expensive battery.
Does your Solar Edge do "Rule 21" or "UL-1741-SA" "frequency-watts"?
If so, could be AC coupled to a battery inverter, which will tell it to reduce output as needed when off-grid.
17kW - does AC output peak that high? Or do inverters have PV arrays of different orientations so it never exceeds maybe 13kW export?
4x Sunny Island would support 17kW.
2x Sunny Island would support 13kW.
You could make a 2x Sunny Island system feeding critical loads panel with one Solar Edge.
Second solar edge on main panel. Manually flip interlocked breakers to put them on Sunny Islands during a power outage.
With addition of a generator transfer switch, that can feed Sunny Island when grid is down (auto-start based on battery SoC if desired.)
Does your Solar Edge do "Rule 21" or "UL-1741-SA" "frequency-watts"?
If so, could be AC coupled to a battery inverter, which will tell it to reduce output as needed when off-grid.
17kW - does AC output peak that high? Or do inverters have PV arrays of different orientations so it never exceeds maybe 13kW export?
4x Sunny Island would support 17kW.
2x Sunny Island would support 13kW.
You could make a 2x Sunny Island system feeding critical loads panel with one Solar Edge.
Second solar edge on main panel. Manually flip interlocked breakers to put them on Sunny Islands during a power outage.
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With addition of a generator transfer switch, that can feed Sunny Island when grid is down (auto-start based on battery SoC if desired.)
The solar edge inverters are rated for a combined 15kw ac. They are new so I’m not planning on replacing them for a hybrid inverter. I’m looking for a ac coupled inverter/chargerSome people replace Solar Edge with StorEdge, but then you need an expensive battery.
Does your Solar Edge do "Rule 21" or "UL-1741-SA" "frequency-watts"?
If so, could be AC coupled to a battery inverter, which will tell it to reduce output as needed when off-grid.
17kW - does AC output peak that high? Or do inverters have PV arrays of different orientations so it never exceeds maybe 13kW export?
4x Sunny Island would support 17kW.
2x Sunny Island would support 13kW.
You could make a 2x Sunny Island system feeding critical loads panel with one Solar Edge.
Second solar edge on main panel. Manually flip interlocked breakers to put them on Sunny Islands during a power outage.
Complete Solar Generator Cabinet w/ QTY 2 SMA Sunny Island 6048 w/ Warranty | eBay
Find many great new & used options and get the best deals for Complete Solar Generator Cabinet w/ QTY 2 SMA Sunny Island 6048 w/ Warranty at the best online prices at eBay! Free shipping for many products!www.ebay.com
400bird
Solar Wizard
There's no need for something experimental.
Outback Radian, Sunny Island(I'm not sure on the model) and others will do what you need.
You need a battery inverter.
What about power outages?
Are you looking to fully disconnect from the grid or simply time shift and consume the energy you produce?
I'm running a Schneider XW pro.
AC coupled to a Solar Edge 6 kW grid tie inverter.
The XW pro isn't recommended unless you've got some programming skills because it won't automatically charge the battery from excess solar production.
It works great! But, I had to program an external controller to set the charging limits on the XW.
One important thing to think about is how much energy you are using overnight and how long you want the battery to support the loads.
Outback Radian, Sunny Island(I'm not sure on the model) and others will do what you need.
You need a battery inverter.
What about power outages?
Are you looking to fully disconnect from the grid or simply time shift and consume the energy you produce?
I'm running a Schneider XW pro.
AC coupled to a Solar Edge 6 kW grid tie inverter.
The XW pro isn't recommended unless you've got some programming skills because it won't automatically charge the battery from excess solar production.
It works great! But, I had to program an external controller to set the charging limits on the XW.
One important thing to think about is how much energy you are using overnight and how long you want the battery to support the loads.
Solar Canada
New Member
I am looking at this type of setup and am thinking about the Schneider XW Pro as well. Can you elaborate on what you mean by programming skills and provide some details on the External Controller you purchased? For reference I have a LiPO battery I built and want to connect to the XW, I'm using a Batrium BMS and will want everything connected together for multiple levels of safety/control.
Thanks in advance for your input.
400bird
Solar Wizard
The limitation for the Schneider XW pro inverter may not apply to your use case.
When grid tied, with AC coupled solar the XW won't initiate a charge cycle or adjust the charge rate to match available power.
If you are off grid, it works great AC and/or DC coupled to PV.
If you are grid tied, it works great with DC coupled solar.
I'm grid tied (with back up and energy shifting) with AC coupled PV (an existing Solar Edge 6kw system), hence I ran into their software limitation.
This is something Schneider could easily address, but they don't seem to have any desire to do so.
My controller is a Raspberry Pi with an energy monitor hat and some software (coded in python) that I modified to controller the XW.
Another member here, is using a standard PLC to do the same.
Very long thread using a PLC:
diysolarforum.com
My thread using the Raspberry Pi:
diysolarforum.com
When grid tied, with AC coupled solar the XW won't initiate a charge cycle or adjust the charge rate to match available power.
If you are off grid, it works great AC and/or DC coupled to PV.
If you are grid tied, it works great with DC coupled solar.
I'm grid tied (with back up and energy shifting) with AC coupled PV (an existing Solar Edge 6kw system), hence I ran into their software limitation.
This is something Schneider could easily address, but they don't seem to have any desire to do so.
My controller is a Raspberry Pi with an energy monitor hat and some software (coded in python) that I modified to controller the XW.
Another member here, is using a standard PLC to do the same.
Very long thread using a PLC:
Adding storage to my Enphase system
I am still fairly new on the forum, tried to answer a few questions as I asked some, and have been talking about my plans and purchases. I figure this is the right place to talk about what I am doing and where it is going. My existing system is a very typical Enphase setup. I have 2 arrays of 8...
diysolarforum.com
My thread using the Raspberry Pi:
Adding Schneider XW Pro
I installed my existing 6kw Solar Edge System, got permission to operate from PGE 12/2018 Now, I am adding battery storage. I started this process nearly a year ago, I submitted the first permit draft in May 2020. Now, in February 2021 I picked up the Conext XW pro and mini PDP. Got it hung on...
diysolarforum.com
Hedges
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Sunny Island works great with AC coupled GT PV inverters, both on and off grid. At least well-behave GT PV inverters that do frequency-watts. Enphase may jump around too much, but you have Solar Edge; haven't read much if anything about AC coupling them (Except 400Bird, above). Off-grid it can manage GT PV wattage up to 2x SI (according to SMA), but on-grid limited to 56A per SI, 6.7kW at 120V so 13.4kW with 2x SI 120/240V stacked.
SI can also have DC coupled PV, either supporting export to grid if SCC pushes battery voltage above setpoint in SI, or not if SCC is under SI's control.
SI does backup, but doesn't appear to do energy time of use shifting, except if programmed to simply connect/disconnect from grid. Would require control by external communications altering its setpoints to accomplish that. I've thought maybe a man-in-the-middle between SI and BMS could do it.
Where I seem to have had issues with my 4x SI + SB system is transition from on to off grid, most recently when electric furnace + pool pump were probably drawing more than a single SI's relays could carry, and grid went down. I had to manually transfer loads back to grid (which had recovered) and restart SI. That may not occur if you stay under the 56A limit of SI. Eventually I will run separate AC wired for excessive load straight to grid, then could likely get by with 2x SI (I installed 4x for the higher bypass current, therefore ran into problems.)
Since you already have Batrium, I think that means you wouldn't get communication with SI. Unless a translator was implemented.
I'm using AGM so no BMS, would look into REC if I did do lithium.
SI can also have DC coupled PV, either supporting export to grid if SCC pushes battery voltage above setpoint in SI, or not if SCC is under SI's control.
SI does backup, but doesn't appear to do energy time of use shifting, except if programmed to simply connect/disconnect from grid. Would require control by external communications altering its setpoints to accomplish that. I've thought maybe a man-in-the-middle between SI and BMS could do it.
Where I seem to have had issues with my 4x SI + SB system is transition from on to off grid, most recently when electric furnace + pool pump were probably drawing more than a single SI's relays could carry, and grid went down. I had to manually transfer loads back to grid (which had recovered) and restart SI. That may not occur if you stay under the 56A limit of SI. Eventually I will run separate AC wired for excessive load straight to grid, then could likely get by with 2x SI (I installed 4x for the higher bypass current, therefore ran into problems.)
Since you already have Batrium, I think that means you wouldn't get communication with SI. Unless a translator was implemented.
I'm using AGM so no BMS, would look into REC if I did do lithium.
Solar Canada
New Member
Amazing stuff guys, thanks for getting involved in the convo. I'm relatively new to this stuff but am SOOO fascinated by it and am going down the rabbit hole head first!! I'm a Mechanical Engineer so consider myself technical but still getting versed on the nuances of the AC Coupled Architecture.
Reason I was thinking Schneider brand is I am setting up our Enclosed Work Trailers with SW Inverters to run an Electric Ladder lift we use to bring PV equipment up and down from roofs and to power miscellaneous items like 20V Dewalt Chargers etc. I'm adding 4 x 480W Panels to the trailer roofs and a Schneider 60/150 CC to each trailer. Leaning towards DIY LiPO but not 100% sure yet, working on options for that portion of the system still. In normal 'off-grid' operation I'm planning to introduce the N-G bond via a bonding plug and then if required remove and charge from this outlet to use the Conext Battery Charger. I was hoping to have to learn only one software program where I can view everything on all the systems but this is not a 100% deal breaker if I need something else for my home AC Coupled system. We haven't entered into GT AC Couple systems for my business so you guys have much more experience in this than I do.
Question - if you were starting today from scratch what would you recommend for the best LV AC Coupled system architecture out there? We almost exclusively install SolarEdge so I would like to stay with this for PV Inverter but am completely open to any High End Battery Inverter Option at this point, not interested in the cheaper Chinese 48V stuff and want something that is reliable and will run well with SE Inverter and my 280Ah 48V Battery Bank (enable curtailment via Frequency Shifting etc.)
Thanks in advance for the input, I can't seem to find a list of options and as I said I'm way down the rabbit hole on this stuff and loving it!
Pete
Reason I was thinking Schneider brand is I am setting up our Enclosed Work Trailers with SW Inverters to run an Electric Ladder lift we use to bring PV equipment up and down from roofs and to power miscellaneous items like 20V Dewalt Chargers etc. I'm adding 4 x 480W Panels to the trailer roofs and a Schneider 60/150 CC to each trailer. Leaning towards DIY LiPO but not 100% sure yet, working on options for that portion of the system still. In normal 'off-grid' operation I'm planning to introduce the N-G bond via a bonding plug and then if required remove and charge from this outlet to use the Conext Battery Charger. I was hoping to have to learn only one software program where I can view everything on all the systems but this is not a 100% deal breaker if I need something else for my home AC Coupled system. We haven't entered into GT AC Couple systems for my business so you guys have much more experience in this than I do.
Question - if you were starting today from scratch what would you recommend for the best LV AC Coupled system architecture out there? We almost exclusively install SolarEdge so I would like to stay with this for PV Inverter but am completely open to any High End Battery Inverter Option at this point, not interested in the cheaper Chinese 48V stuff and want something that is reliable and will run well with SE Inverter and my 280Ah 48V Battery Bank (enable curtailment via Frequency Shifting etc.)
Thanks in advance for the input, I can't seem to find a list of options and as I said I'm way down the rabbit hole on this stuff and loving it!
Pete
MurphyGuy
It just needs a bigger hammer
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There are really no good options to do time-of-day load shifting to compensate for the crappy net metering rules some states have. When I installed my solar here in Michigan, we had an eggs-for-eggs agreement. I give them a kWh, they have to give it back for free whenever I want it. No money ever changes hands unless I draw more juice than I have "banked up".
I'm grandfathered in for 10 years, but the new rules are they sell it to you for 18 cents and buy it back from you for 6 cents on a minute by minute basis. So basically, you have to give them 3 times as much energy to get 1 unit back free.
As I have done a little research on trying to solve this issue when the time comes and my grandfathered benefits switch over to the new rules, I have found there are no good solutions except to go entirely off-grid and only use the grid power for emergency days when the sun doesn't cooperate.
As far as "the best system for ac coupling", that would depend on what you consider to be important. SolArk units have all kinds of bells and whistles, fancy interfaces, one-box-does-it-all, etc, but they are built cheaply and are High Frequency inverters that do not handle big in-rush currents well.
The all time king of robustness and reliability are the SMA Sunny Island units. Seriously, there isn't anything that even comes close to their quality, but while they are strong in the reliability department, the user interface is a 2 line dot matrix display and you need to squint to read it.
How you configure your system is going to depend on how you use energy and how your poco charges you for it. The marketplace is a bit behind in this regard and is probably going to need some time to catch up.
Hedges
I See Electromagnetic Fields!
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SMA invented it. Also transformerless grid-tie inverters.
"LV AC coupled"? LF AC coupled?
Their Sunny Island + Sunny Boy work very well together. Can be split-phase or 3-phase.
What I don't think it supports well if at all is controlling import/export for time of use. They sell Sunny Boy Storage for that, HV, HF, AC coupled, wimpy.
I suspect new European model Sunny Island will support UL-1741-SA and time shifting when brough to the US.
I now use Sunny Web Box (obsolete) with RS-485 to SI and Ethernet to laptop.
Not sure if Sunny Explorer (PC software) could do it.
User interface should be set it once and forget it. Unless the green LED changes to red.
MurphyGuy
It just needs a bigger hammer
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I have the Sunny Explorer software.. horrible stuff. Takes like 2 minutes just to boot up and you have to sit there and keep clicking on all the dumb boxes to finally get to the main screen.. and the main screen is pretty useless as there's nothing there that isn't in the inverter's own web interface (that boots up almost instantly!).
As for the Sunny Islands, there's no way to communicate with them unless one purchases the ridiculously expensive extra boxes for them.
But I'm fine with it. My number 1 priority is robustness and reliability, and the Sunny Islands are, by far, the leader in those departments.
Solar Canada
New Member
We have a 1:1 Net Meter arrangement here in Ontario, credits are available for 12 months from day we send it back to grid. In regards to my 'LV' notation I was referring to low voltage battery AC Couple (ie - 24/48V) vs high voltage (ie - 400V LG Chem/SE Energy Bank/etc). I would like to use my 48V LiPO Battery bank as back-up.
I will almost certainly be using SolarEdge for my PV Inverter as I have extensive experience with this and my home is NOT built for solar - semi-detached with almost full North Facing roof - and I'm looking for best efficiency (>99% AC/DC), Panel level monitoring, and Shade Mitigation features. I have read there are some Hybrid Inverters for AC Couple Battery Back-up configured to talk to SolarEdge but I can't find a comprehensive list and looking for opinions from anyone who has experience with this.
I will almost certainly be using SolarEdge for my PV Inverter as I have extensive experience with this and my home is NOT built for solar - semi-detached with almost full North Facing roof - and I'm looking for best efficiency (>99% AC/DC), Panel level monitoring, and Shade Mitigation features. I have read there are some Hybrid Inverters for AC Couple Battery Back-up configured to talk to SolarEdge but I can't find a comprehensive list and looking for opinions from anyone who has experience with this.
Hedges
I See Electromagnetic Fields!
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No experience with Solar Edge, but for certain reasons I might use it in my next install.
Sunny Boy has adjustable voltage and frequency parameters. I've widened frequency of some UL-1741 operating behind Sunny Island to the limits of UL-1741-SA. Off-grid they support much wider voltage and frequency, intended to remain on-line if a generator is feeding in.
Your chosen brand may also allow some such adjustment.
"talk to SolarEdge" by a data bus?
SolArk and Skybox (plus its newer replacement) of course are LV HF hybrids that support AC coupling. At least to some extent, as we've been following the tribulations of people trying to use SolArk with 100% of PV AC coupled.
The need for shade mitigation is really only a thing if you have two or more PV strings connected in parallel, and shade will affect a significant percentage of panels in one string but not the other. If you can plan your shade wisely, then just parallel them. If you use an inverter with separate MPPT input per PV string (e.g. Sunny Boy -41), each is independently optimized.
Better read up on the failure rates of Solar Edge and its optimizers. I started one.
diysolarforum.com
We're reading of installers who stopped using them.
"best efficiency (>99% AC/DC)"?
That's not what matters anymore. Might have when PV was $5/watt.
Looks for best W/$ and reliability.
Sunny Boy has adjustable voltage and frequency parameters. I've widened frequency of some UL-1741 operating behind Sunny Island to the limits of UL-1741-SA. Off-grid they support much wider voltage and frequency, intended to remain on-line if a generator is feeding in.
Your chosen brand may also allow some such adjustment.
"talk to SolarEdge" by a data bus?
SolArk and Skybox (plus its newer replacement) of course are LV HF hybrids that support AC coupling. At least to some extent, as we've been following the tribulations of people trying to use SolArk with 100% of PV AC coupled.
The need for shade mitigation is really only a thing if you have two or more PV strings connected in parallel, and shade will affect a significant percentage of panels in one string but not the other. If you can plan your shade wisely, then just parallel them. If you use an inverter with separate MPPT input per PV string (e.g. Sunny Boy -41), each is independently optimized.
Better read up on the failure rates of Solar Edge and its optimizers. I started one.
Solar Edge - an installer's blog
Came across the following blog. It includes the company's installed system numbers and failure rates for SolarEdge, Fronius, Enphase. Also, information on limitations and best use of optimizers. https://www.mcelectrical.com.au/solaredge-inverter-optimiser-review/
diysolarforum.com
We're reading of installers who stopped using them.
"best efficiency (>99% AC/DC)"?
That's not what matters anymore. Might have when PV was $5/watt.
Looks for best W/$ and reliability.
