Sol-ark question re additional AC coupled array

[Judoal]

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

 

[MaikaiLifeDIY]

AC coupling is a good way to bring additional power in to the Sol-Ark to be used for charging your batteries and/or powering your loads.

Assuming you switch your 4th array to micro inverters you can then hook them into your generator input on your Sol-Ark.

If you wanna keep that Outback FM 60 CC hooked to your additional panels then you’ll have to tap into your DC side. This would connect to your DC system probably on the bus bar and feed into your batteries.

Sol-ark is releasing their own micro inverters in Q1 2024 otherwise you can look at other brands.

Check out page 10 on the the sol-ark 12k manual for a diagram of AC coupling.

https://www.sol-ark.com/wp-content/uploads/12K-2P-N_Manual.pdf

 

[Ampster]

I also have a SolArk with both DC coupled and AC coupled arrays. My AC coupled array is 9 kW and my DC coupled arrays are about 3kW which if I had to do it over I would have more DC coupled solar. It is not an issue 98% of the time but when the grid is down the AC coupled arrays do not get utilized unless have enough loads or batteries to charge. In the OPs situation they could convert that string to micros or a small GT inverter to get the benefit of AC coupling. Currently with Voltage of only 100 volts that is too low for the MPPT controller of the SolArk. I have six old panels (1.4kW) that I doubled up with some high voltage Enphase micros which I placed on my greenhouse roof. In my case they were not enough voltage for a separate GT inverter. The flexibility of wiring in 3 Enphase inverters and the 240 volt wiring is much simpler than DC strings.

 

[Judoal]

the microinverter is too expensive as far as I can tell. Because the FM60 has wiring in place for the array and the batteries, it makes more sense to me to replace it with a new inverter/charge controller at much lower cost,

 

[MaikaiLifeDIY]

What is it that that existing Outback charge controller is not doing or would be better with some other brand?

 

[Judoal]

I’d dump the FM60 in favor of an inverter charger. All necessary connections are in place.

 

[Ampster]

the microinverter is too expensive as far as I can tell.

Hard to tell without knowing how many panels you have? If they are low enough voltage you could use two panels per micro, which would be half as many micros. Yes wiring would be simpler if string inverter can handle voltage. Do you know how panels are wired? Are they in series or a combination of series and parallel?

 

[Judoal]

The array has 12 panels, wired as 4 groups of 3 panels. See attached for panel specs.

 

[Ampster]

Three panels is just over 100 volts per string. I tried three panels in series on my SolArk and the voltage was barely enough to produce some energy. Can you verify the voltage on each MPPT?

 

[Ampster]

the microinverter is too expensive

Three micros would only be $450 for three micros and I am not sure you could find a UL approved GT inverter for less.

 

[Judoal]

One issue is the max input voltage. Each string of 3 panels has Voc=~100vdc. The enphase microinverter has a max voltage of 60 v. Reducing the string to 2 panel would still have an open circuit voltage that is greater than 60 v. Even considering the peak output voltage of 28.5 v per panel, stringing 2 panels in series put the voltage very near the max voltage of the enphase inverter. At less than peak conditions, the voltage will be greater than 60v.
.

 

[Ampster]

The enphase microinverter has a max voltage of 60

There are some micros that can handle more voltage. I found a IQ8x BAT which might work. I used some IQ7x micros that were designed for 96 cell panel. However two panels might still be the max.

 

[Judoal]

I would need 6 units and a fair amount of rewiring an adding 2 more breakers in my combiner box

 

[Ampster]

I would need 6 units and a fair amount of rewiring an adding 2 more breakers in my combiner box

Is your combiner box DC or AC? If you added six panels AC coupled you would only need one double pole breaker for the micros. Presumably that would be connected to the generator port of the SolArk. Unless you doubled up the panels as I suggested earlier you would need six micros and that cost plus an Envoy would be close to the cost of a GT string inverter. The Envoy might be optional because the SolArk will report solar generation on the generator port. Only you would know the time and cost difference between running DC to a string inverter versus adding three or six micros and running a separate AC circuit.

 

[Judoal]

My other option is running DC to an inverter/CC next to the Sol-Ark. All wiring from array and batteries is right there. Have to see how much I can spend and how much work I want to do. My array is tall and rewiring on a ladder will be a pain (from past experience).

 

[400bird]

Maybe I missed it, but why not just leave the current array on the charge controller and let it charge the battery?

Depending on your usage, that may be more efficient than AC coupling - converting DC(PV) > AC > DC(battery)

Also probably less expensive as you've already got the components.

 

[zanydroid]

You can overpanel by 2 panels into one input on HMS1600 4 port microinverters and still end up ahead.

So one HMS1600 (4 port) one HMS800 (2 port). 2400W at 240v operating voltage is fine to go on a 15A branch circuit.

If you do not have at least #14 to the array there’s no way you can do microinverters or grid tie inverters. Not even sure there is a GTI with low enough output for #14

 

[zanydroid]

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

 

[zanydroid]

Another option is, if it’s parallel combined on the ground convert it to series within the combiner (assuming all panels are producing similar enough current still) to get to 300V. So no work inside the array. That will be closer to the sweet spot of GTIs than 100V will be

 

[Judoal]

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 think I found a hybrid inverter that could work as an AC input (https://signaturesolar.com/growatt-48v-6kw-250vdc-split-phase-off-grid-inverter/). Will this work? Any info about this inverter? Would it work with this unit connected to the sol-ark and the battery?

thanks