Need to convert Grid-Tie to Battery with Net Zero export (Sol-Ark, Fortress)

[wpns]

My "HOA/Power Co-Op" has recently passed rules against Net Metering (because reasons), and the power quality of our grid keeps getting worse (frequency excursion of +/- 5 Hz(!), etc), and my many individual UPS batteries need replacing, so it's time for the Whole House UPS paradigm, and batteries seem to be getting cheaper.

My current system is:
Ground Mount south facing planar array, 12KW panels in 3 parallel strings of 15 panels each, 10KW SMA Grid-Tie inverter, works fine.
Roof-mount, two arrays (east and west-facing) of two strings each (10 and 9 panels per string) 15K total, with two GoodWe 7600A inverters, also works fine.
However, to add batteries it looks like I need new inverter(s).

I'm being quoted Fortress eVault Max 18.5 KWHR batteries for around $10K and Sol-Ark 15K all-in-one inverters at around $7K each. But I had a couple of questions for the experts here, who probably have some experience with the above systems in isolation, or hopefully in combination:

eVault Max 18.5kWh LFP Battery ® - Fortress Power

The newest innovative Lithium Iron Phosphate battery from Fortress Power is the eVault Max 18.5 kWh ®. An all-in-one solution for your residential and

www.fortresspower.com

Sol-Ark 15K All-In-One

Sol-Ark® 15K-2P solar hybrid inverter is powerful and military-grade that is scalable, battery-agnostic, and a true whole home backup. Learn more.

www.sol-ark.com

0) Are the above decent companies with products that can reasonably be expected to last decades? I've seen much lower prices, but I want a company that'll still be around in 10 years...

1) The Sol-Ark inverters have 3 MPPT inputs, which fits well with the planar 3-string array. But the roof-mount array is 10-string and 9-string on either side of the roof. How can I (or can I?) connect 4 strings to 3 MPPT inputs?

2) The budget and available space fits 3 of the Fortress batteries, and it looks like I need to connect all the batteries and inverters in parallel, is there a good recommendation for a DC combiner that'll connect (3) 180A batteries and (2) 275A inverters?

3) I'm still studying the manuals, but how do you parallel two of the Sol-Ark 15K inverters on the AC side?

Thanks in advance for any advice!

 

[robby]

I am using the Sol-Ark 12k and basically 6x Fortress eFlex batteries. With 10.2Kwp of Solar.
Both companies offer excellent customer service and warranty support.

1) I am not sure what four strings you plan on using but you could keep one of the original inverters and have it feed power to the Sol-Ark.

2) There are plenty of combiners available.
I suggest you contact Dexter at Current Connected.
He has the Sol-Ark and the Bus Bars plus he is a fortress power dealer.

3) The manual has a diagram in it for paralleling two 15K units.

 

[wpns]

3) The manual has a diagram in it for paralleling two 15K units.

(Finally) found it, thanks! Looks like the AC grid and load connections need to be paralleled, so I need AC combiners, I'll look into the options.

 

[wpns]

1) I am not sure what four strings you plan on using but you could keep one of the original inverters and have it feed power to the Sol-Ark.

I have four strings on the roof:

9-panels facing East
10 Panels facing East

9-panels facing West
10 Panels facing West

My brain wants to say that if I connect 9-panel and 10-panel strings in parallel it'll bring the 10-panel string down to the 9-panel string's voltage, or the MPPT will get confused in some other way.

Likewise, connecting the 9-panel East-facing string and the 9-Panel West-facing string will not (fully?) capture the power from the string that's not as fully sunlit as the other side.

Does that make sense, or will the MPPT do a "good enough" job?

Thanks!

 

[1201]

@wpns what are the new rules against net metering? Is it a switch to buy back? Do they pay you anything for export?

Also, just so you know, for $10k diy you can get about 70kwh of battery storage instead of 18.5kwh buying a premade battery

 

[robby]

I have four strings on the roof:

9-panels facing East
10 Panels facing East

9-panels facing West
10 Panels facing West

My brain wants to say that if I connect 9-panel and 10-panel strings in parallel it'll bring the 10-panel string down to the 9-panel string's voltage, or the MPPT will get confused in some other way.

Likewise, connecting the 9-panel East-facing string and the 9-Panel West-facing string will not (fully?) capture the power from the string that's not as fully sunlit as the other side.

Does that make sense, or will the MPPT do a "good enough" job?

Thanks!

What are the Specs on these Panels. Wattage, Vmpp and Impp.
Are they all the same model Panel?

 

[DIYrich]

Why do you want 2 sol-arks? If you do have 2, then that gives you 6 mppts for your 4 strings.

Get the eg4 powerpro battery. Much cheaper.

If you just get 1 solark:
If your 10/9 panels have no shading issues, then make 4 strings of 9 panels, run each 9 into the two connections for each mppt, put micros on the remaining two and run them as ac pv.

 

[LydMekk]

I would buy something else than Fortress batteries.
There has been some stories in here...
I do recommend the Sol Ark though. Very nice gear.

 

[frasere2]

What company offers the same inverter for 10 years? If you are under warranty, I'm sure they don't give you the same inverter, so you will pay the upgrade price (unless they upgrade you for free). Also, put optimizers on your panels and you will increase the production10-20%, they are cheap, like $45 each. You are ground mounted so it will be an easy install. And to add batteries, can't you use an AC coupling? The inverter cost should be much cheaper.

 

[DIYrich]

I missed the part that you have ground mount and roof top solar.

Get one sol-ark 15k. Put one of the solar into the 15k as DC PV. Keep the other as-is, and put into the sol-ark Smart Load port as AC PV.

I would probably put all the ground mount into the sol-ark: string 1 and string 2 into mppt 1; string 3 into mppt 2, and the largest roof string into mppt 3.

 

[wpns]

Not to hijack my own thread but I've got a pair of Honda EU3000is generators (2.5KW each) that can be paralleled, but only make 120V, can the generator input be set to load a single 120V generator, or must it be a 120/240 input? [Yes, I can play some games with autotransformers, but I'd rather not...]

 

[wpns]

what are the new rules against net metering?

Well, it's an ""HOA", and they demonstrably don't understand what it means. They think that if they pay me for my power that it'll evaporate and not go to another load (where they get paid for it), so I'm causing them a financial loss. Net Zero (never push power back into the grid) will cover it.

 

[wpns]

Also, just so you know, for $10k diy you can get about 70kwh of battery storage instead of 18.5kwh buying a premade battery

Probably true, (pointers?) but will my wife be able to run/maintain if if I get hit by a beer truck? She's already (legitimately) concerned about the number of bespoke monitoring and control systems around here...

 

[DIYrich]

Not to hijack my own thread but I've got a pair of Honda EU3000is generators (2.5KW each) that can be paralleled, but only make 120V, can the generator input be set to load a single 120V generator, or must it be a 120/240 input? [Yes, I can play some games with autotransformers, but I'd rather not...]

Sol-ark requires split phase 240v. Chargeverter can run on 120, but at half the capacity, so you would need 2.

 

[wpns]

What are the Specs on these Panels. Wattage, Vmpp and Impp.
Are they all the same model Panel?

I'll have two dig up the details, but the ground-mount array is (45) 260W panels in 3 strings to a DC combiner and then the SMA grid-tie inverter, and the roof-mount is (38) 405W panels in 4 strings into the two GoodWe inverters. Too much to put them all into a single 15K inverter, which is why I think I need two. Two would give me 6 MPPT inputs, but I have 7 strings...

 

[1201]

Probably true, (pointers?) but will my wife be able to run/maintain if if I get hit by a beer truck? She's already (legitimately) concerned about the number of bespoke monitoring and control systems around here...

No. She'll have to sell all of it. That will probably be the case if you build a diy battery or buy an evault.
The batteries, once they are setup, don't need a lot of hand holding.

It's still a good idea to provide some basic training to your spouse, for example how to switch back to the grid if the system goes down.

 

[wpns]

Get the eg4 powerpro battery. Much cheaper.

Looks like it. Is it also 'better' to build the system with EG4 18K hybrid inverters? Looks like you get a 12-year warranty if you use all EG4 equipment.

 

[DIYrich]

Looks like it. Is it also 'better' to build the system with EG4 18K hybrid inverters?

Looks like there are some Version 1 problems with the 18kpv. Otherwise it looks like a great unit. Up to you if the $1,500 difference is worth the potential bother.

Not so much worried about the powerpro. A battery is a battery. Worst case, you disconnect the communications and run it in voltage mode.

 

[wpns]

Chargeverter can run on 120

This looks like a much better solution, I take it the inverter(s) don't get confused if something external is charging the batteries?

 

[DIYrich]

This looks like a much better solution, I take it the inverter(s) don't get confused if something external is charging the batteries?

You have to be careful about charging current. Otherwise inverters see voltage, and are happy.