Sol-ark question re additional AC coupled array

[Judoal]

ladder

K.

I have a new Sol-Ark 12K grid connected battery (48v) backed up system. its running on 3 of my 4 arrays. The 4th array has a different voltage and can’t be connected. It is nominally rated at about 2500 watts, but should be down graded due to age. The Voc is 100v, and the voltage under full sun is less than 85v. While the 4th array is running through an Outback FM 60 CC, it is essentially very under utilized providing a slight charge to the batteries. I am looking for a solution to better utilize this array. I understand that the Sol-Ark system has an auxiliary AC input. Can this be used using the 4th array as an AC coupled array with a new inverter scrapping the FM60 CC. Thanks

I have a new Sol-Ark 12K grid connected battery (48v) backed up system. its running on 3 of my 4 arrays. The 4th array has a different voltage and can’t be connected. It is nominally rated at about 2500 watts, but should be down graded due to age. The Voc is 100v, and the voltage under full sun is less than 85v. While the 4th array is running through an Outback FM 60 CC, it is essentially very under utilized providing a slight charge to the batteries. I am looking for a solution to better utilize this array. I understand that the Sol-Ark system has an auxiliary AC input. Can this be used using the 4th array as an AC coupled array with a new inverter scrapping the FM60 CC. Thanks

I don’t think that using microinverters will work. There are only two wires from the combiner box, with the negative side ground. I don’t see how to get a split-phase output from microinverters to the sol-ark for AC coupling.

 

[Judoal]

FM60 into the battery is architecturally a lot simpler.

Personally the only hard reason I can think of to not do that is invalidation of UL9540 cert.

Things like more complex SoC, can probably be solved

this is what have now. The max power from the array is only 250w. The array is 2500w.

 

[zanydroid]

I don’t think that using microinverters will work. There are only two wires from the combiner box, with the negative side ground. I don’t see how to get a split-phase output from microinverters to the sol-ark for AC coupling.

Microinverters are generally 240V output with L-L-G or L-L AC trunk cables.

Negative side ground may force a modern microinverter or MPPT to flip out.

What is causing the underperformance on the FM60

 

[Judoal]

The CC and the sol-ark are connected to the battery. The sol-ark registers about a 170w draw from the batteries while the battery is maintaining just 0.1v or 0.2v above float voltage. This does not happen without the CC.

 

[zanydroid]

I see, so you don’t know what is misconfigured or broken. There is a possibility that it’s a SolArk config/reporting issue, but I don’t have one so I don’t know how to go about debugging it. Maybe DC clamp meter and get some more intel about the power movement.

You should be able to use any 1741SA grid tie inverter, with the constraints being DC side voltage and random incompatibility issues with grid forming. Enphase IQ8 are the main ones people rant about as having compatibility issues.

Note many grid tie inverters are 240V L-L-G wired and typically for ungrounded systems so same confusion / mental model fix needed as for microinverter post a few messages up.

 

[Judoal]

I seem to remember seeing a setting for preference between battery and array but Either I’m misremembering or I can’t find it

 

[Judoal]

Microinverters are generally 240V output with L-L-G or L-L AC trunk cables.

Negative side ground may force a modern microinverter or MPPT to flip out.

What is causing the underperformance on the FM60

 

[Judoal]

I seem to remember seeing a setting for preference between battery and array but Either I’m misremembering or I can’t find it

The sol-ark is “hard wired” to use array power first then battery then grid.

 

[n2aws]

While the 4th array is running through an Outback FM 60 CC, it is essentially very under utilized providing a slight charge to the batteries. I am looking for a solution to better utilize this array.

I'm not sure I actually understand this statement. The charge controller should be able to handle 100% of what this array is producing. How is it underutilized? You have the equipment already.. whereas, to switch it over to an AC coupled scenario, you'd have to buy more gear.. and then what are you doing with the charge controller? Unless you sell it, or install another array to use it.. then it's even more underutilized

 

[Judoal]

I'm not sure I actually understand this statement. The charge controller should be able to handle 100% of what this array is producing. How is it underutilized? You have the equipment already.. whereas, to switch it over to an AC coupled scenario, you'd have to buy more gear.. and then what are you doing with the charge controller? Unless you sell it, or install another array to use it.. then it's even more underutilized

The CC is connected to the battery, as is the sol-ark inverter. the inverter seems to be limiting the power from the battery. to about 170w going to the load and the grid along with the several kw from the 3 arrays connected to the inverter. I don’t know how to change this. The inverter has the max discharge amps from the battery at 185a, so that isn’t the limiting factor. it should sell power to the grid over what is required for the load.

 

[zanydroid]

I see so the question is around how to configure the SolArk in DC coupling mode to grid sell, without any communications with the MPPT.

Did you contact SolArk support?

I would recommend creating or searching for a post on how to convince SolArk to start selling based on an estimate of an external charge controller. My guess is some kind of rough SoC based rule is about as good as you can get without communications to the CC. That is, when DC coupled without communications the inverter doesn’t really know how much surplus power is available. Pretty sure similar issues would happen with EG grid tied Schneider or Victron using third party charge controllers

You would need to ask around to see if AC coupling behaviors closer to the way you want. I doubt it is guaranteed to be as configurable as selling from the MPPTs baked into the SolArk, though it may end up being closer to what you want.

 

[Judoal]

I see so the question is around how to configure the SolArk in DC coupling mode to grid sell, without any communications with the MPPT.

Did you contact SolArk support?

I would recommend creating or searching for a post on how to convince SolArk to start selling based on an estimate of an external charge controller. My guess is some kind of rough SoC based rule is about as good as you can get without communications to the CC. That is, when DC coupled without communications the inverter doesn’t really know how much surplus power is available. Pretty sure similar issues would happen with EG grid tied Schneider or Victron using third party charge controllers

You would need to ask around to see if AC coupling behaviors closer to the way you want. I doubt it is guaranteed to be as configurable as selling from the MPPTs baked into the SolArk, though it may end up being closer to what you want.

Sol-ark said the simplest solution would be to add a 2nd 12k unit in parallel. A bit overkill methinks for a 2500 w array along with I have more room for a large unit like that and I can’t afford it. I’ll keep looking for a GT split-phase inverter for AC coupling with the Sol-ark inverter

 

[zanydroid]

Sol-ark said the simplest solution would be to add a 2nd 12k unit in parallel. A bit overkill methinks for a 2500 w array along with I have more room for a large unit like that

Of course they would say that, but what about changing the sell settings to approximate what you want.

 

[Judoal]

Of course they would say that, but what about changing the sell settings to approximate what you want.

That should have been no more room

 

[n2aws]

The CC is connected to the battery, as is the sol-ark inverter. the inverter seems to be limiting the power from the battery. to about 170w going to the load and the grid along with the several kw from the 3 arrays connected to the inverter. I don’t know how to change this. The inverter has the max discharge amps from the battery at 185a, so that isn’t the limiting factor. it should sell power to the grid over what is required for the load.

Can you please take a moment to clarify this?

Are you saying that, no matter what the load is, or how depleted the batteries are, you never see more than 170 watts going from the inverter to your protected loads? I'm not trying to be "difficult", honestly. I'm just trying to understand exactly what it is you are expecting to happen, vs what is actually happening. From what I've read so far, this sounds a lot like an inverter misconfiguration. Forgetting the 4th array and separate charge controller.. your inverter, batteries, and the strings of panels going into the solark directly should be letting you nearly max out the solarks output when needed.

If you are saying that no matter what, the most you ever see the solark invert is 170 watts.. I'd have to assume you only have 170watts of loads for some reason, or you've got a setting somewhere that is telling the solark to not produce more than 170watts. Neither of which, should have anything to do with the 4th array and separate charge controller. My bet is, if you turned that charge controller off completely, you'd see the same behavior.

If my assumptions are incorrect, please elaborate on what is actually happening versus what you expect or want to happen. Screenshots showing configs, and screenshots showing the "behavior" would likely help. (well, they may help someone who is familiar with sol-ark, which.. is not me.. but based on the info provided in this thread so far, I think there is a bit of a "wild goose chase" or "red herring" going on here.)

From what I *think* you are saying here, I suspect you only have 170watts on the "protected loads" side, and you think the inverter should be selling the excess PV power to the grid. I *suspect* that your grid sell settings are the problem here, more than the 4th string and charge controller

 

[zanydroid]

These are great prompts for more information.

On the previous trajectory of the thread, there's very little chance of improving the system.

I'd recommend maybe spamming some graphs and screenshots too (preferably in raw form and annotated with what you expect/want to see) since that diversifies away from getting bogged down in converting to English in a mutually understandable way.

 

[Hedges]

The 4th array has a different voltage and can’t be connected. It is nominally rated at about 2500 watts, but should be down graded due to age. The Voc is 100v, and the voltage under full sun is less than 85v.

I think that may not be normal degradation, maybe a couple bad panels.
I think Voc and Vmp would only drop a little bit with age, although I'm not sure.

I had two identical strings of panels, and one was delivering half the current of the other in operation (based on clamp ammeter.) I tested each panel for Voc and Isc, finding 3 bad panels out of 24. Testing for Vmp and Imp (or actually as loaded with resistance, space heaters), I identified 2 more bad.

To couple with SolArk, consider a used string inverter, connected to the generator port. Doesn't even have to have frequency-watts; SolArk will ramp down power from its DC connected panels, then disconnect the AC coupled GT inverter and ramp up from DC panels. So long as DC coupled watts > AC coupled watts, should operate smoothly.

 

[Judoal]

The panels on the array are all good. To answer @n2aws, the CC is connected to the DC side at the batteries. It is delivering power from there through the S-A inverter to the grid and the load in addition to the power generated by the 3 arrays connected to the S-A inverter. The problem is that the inverter is limiting the power generated by the CC (not by the other arrays connected to the inverter. I don’t why the power generated by the CC should be limited, since the grid can take as much as I send it.

Before I replaced my previous, all arrays were working fine, with all 4 arrays delivering expected power, before I replaced my old system, with some degradation due to age.

Also as I’ve stated in my previous posts, string or micro inverters won’t work. The combiner boxes were wired years ago as two wire system with the negative side of the arrays being grounded and therefore not able to deliver split-phase AC to the inverter from the micro/string inverters.

 

[n2aws]

The problem is that the inverter is limiting the power generated by the CC (not by the other arrays connected to the inverter. I don’t why the power generated by the CC should be limited, since the grid can take as much as I send it.

I think you're making an incorrect assumption here. If the sol-ark, and charge controller aren't doing closed loop communications, there is no way for the sol-ark to actively limit the amount of power generated by the CC. If there is "power to consume" and enough available solar array to provide the power, the CC will produce it.

I suspect the problem is the opposite of your assumption. The sol-ark doesn't *know* about the additional current/capacity, and thus can't make intelligent decisions on how much power to send back to the grid based on the "excess". The sol-ark is likely balancing "available power" and "power to deliver to the grid", completely unaware that there is something else adding power on the DC bus.

With that in mind, I think the sol-ark is only "limiting" your CC output because it's only selling back the power it knows about. And because it's doing a good job of it, there is nowhere for the "excess" power to go from the CC.


So, as others have suggested, you can change the settings to tell the sol-ark to deliver "slightly more" to the grid during a ToU window, or you can increase the loads on the protected loads side.

Obviously, you can throw more money at the problem by buying hardware to AC couple it, but for 2kw, is it worth it when the other options are free? That answer depends entirely on your situation. If the other arrays cover the majority of your bill, then I suspect even the AC coupled capacity would be "wasted". The other side is, what is the cost to buy the microinverters or other hardware involved to convert that 2kw to AC coupled.. and the payback time? Is it better to make a couple setting adjustments to utilize as much of it as you can now, or is it better to buy the hardware, and utilize as much of it as possible? The payback period probably would be the deciding factor in my opinion.

 

[Judoal]

I think you're making an incorrect assumption here. If the sol-ark, and charge controller aren't doing closed loop communications, there is no way for the sol-ark to actively limit the amount of power generated by the CC. If there is "power to consume" and enough available solar array to provide the power, the CC will produce it.

I suspect the problem is the opposite of your assumption. The sol-ark doesn't *know* about the additional current/capacity, and thus can't make intelligent decisions on how much power to send back to the grid based on the "excess". The sol-ark is likely balancing "available power" and "power to deliver to the grid", completely unaware that there is something else adding power on the DC bus.

With that in mind, I think the sol-ark is only "limiting" your CC output because it's only selling back the power it knows about. And because it's doing a good job of it, there is nowhere for the "excess" power to go from the CC.


So, as others have suggested, you can change the settings to tell the sol-ark to deliver "slightly more" to the grid during a ToU window, or you can increase the loads on the protected loads side.

Obviously, you can throw more money at the problem by buying hardware to AC couple it, but for 2kw, is it worth it when the other options are free? That answer depends entirely on your situation. If the other arrays cover the majority of your bill, then I suspect even the AC coupled capacity would be "wasted". The other side is, what is the cost to buy the microinverters or other hardware involved to convert that 2kw to AC coupled.. and the payback time? Is it better to make a couple setting adjustments to utilize as much of it as you can now, or is it better to buy the hardware, and utilize as much of it as possible? The payback period probably would be the deciding factor in my opinion.

can’t use micro inverters. The combiner boxes have the negative side grounded and can’t deliver split-phase power for AC coupling. Only other solution is a small inverter to replace the CC. Space is limited.

i have an all electric house so additional power is necessary.