assistance with hybrid selection

[secondhandluck]

I am currently designing a system, that was originally intended to be strictly grid tied. I do have the panels and mounts for 3 strings of 8 Sunpower 305 panels, and they would work perfectly with a SMA SunnyBoy 7.0. It has three MPPT inputs, and their voltage limits work perfectly with my panel output.
But, I am having second thoughts and am considering a hybrid inverter, for the battery backup more than anything. So, after looking around this opens pandoras box, and I have more questions than answers.
The issues at first glance:
1. Many are limited to 48v DC input. I do like the Schneider Context 6848 as it can be configured for many battery types, but my panels are 58v so it's a no-go.
2. Many are built to work with specific batteries, which are out of my budget. For instance, the Solar Edge is made for the LG battery, and the Generac units only use the Generic batteries. I have the ability to purchase Trojan lead/acid for cheap, and would prefer that over a 6k Li battery.
3. Number of MPPT ports, The SunnyBoy 7.0 has three MPPT ports rated at 600V/ 700V max but I haven't found any Hybrid Inverter that is comparable.
I'm limited by what I can find searching through catalogs online, and staring at spec sheets, which is a lot of info but I'm sure I'm missing something. If anyone can point me towards a suitable hybrid, I would be most grateful.

FWIW, this system will be mounted on my barn roof here in S Jersey. I have been collecting bits and pieces for about a year, and just scored the panels and mounts. While I'm doing this cheaply, I am committed to buying the inverter new. My background is construction/ welding/ mechanic so much of this is familiar. I've helped install a few systems, but this is my first from start to finish.
Let me know if I've missed any important info that's needed, and thanks in advance.
SD

 

[Hedges]

As an option other than hybrid, that Sunny Boy should have "Secure Power", which lets you flip a switch and get 15A 120VAC from an outlet while the grid is down but sun is up (no battery). (So long as you don't have "Rapid Shutdown", which isolates panels during power failure; that is a code requirement in some locations for rooftop but maybe not barntop.)

You can pick up SI6048 for $2000 or so. I see those (and the Sunny Boys) new on eBay. Two of these, or one of them with a suitable 120V/240V transformer, would play with the Sunny Boy to work on and off grid. That would support 48V lead-acid as well as expensive Li. If you follow vendor's recommendation for sizing battery as 100 Ah per kW of PV you'll have a 700 Ah 48V battery. My battery is about 1/3 of what they recommend.

MPPT ports - You don't have to get more than one. If all strings are the same Voc, paralleling different orientations isn't a big deal. Even one panel shaded in one string doesn't make it operate far from optimum. Where it does matter is if one string has all 8 panels exposed to sun and the other has 4 panels shaded - you may only get the production of one string.

What's the problem with using your PV panels on the Schneider 6848? I don't see PV input specs on their data sheet, only battery; it may require a separate charge controller for PV.

https://41j5tc3akbrn3uezx5av0jj1bgm-wpengine.netdna-ssl.com/wp-content/uploads/2020/01/DS20200409_Conext-XW-120-240-V.pdf

 

[svetz]

Hi SD,

Welcome to the forums!

I liked Sol-Ark the best, but ended up going with Enphase and an AC battery in the end due to issues that couldn't otherwise be resolved.

..... Many [hybrids] are limited to 48v DC input. I do like the Schneider Context 6848 as it can be configured for many battery types, but my panels are 58v so it's a no-go...

The solar panel string voltage is usually higher than the battery voltage. In the U.S., the maximum voltage of a string 600 V (after temperature correction). What happens is the Solar DC volts/amps goes into your solar charge controller (e.g., MPPT) which reduces the voltage to one of the three most common battery voltages (i.e., 12, 24, or 48V).

...2. Many are built to work with specific batteries, which are out of my budget. For instance, the Solar Edge is made for the LG battery, and the Generac units only use the Generic batteries. I have the ability to purchase Trojan lead/acid for cheap, and would prefer that over a 6k Li battery.

Here's a partial list of hybrids, most of them will work with any battery of any chemistry.

...3. Number of MPPT ports, The SunnyBoy 7.0 has three MPPT ports rated at 600V/ 700V max but I haven't found any Hybrid Inverter that is comparable.

The Sol-Ark handles 6 500V strings (2 strings per MPPT).
It's good to have more MPPT ports as each port will optimize the panels fed into it. If there is no shade and they all have the same angle, it's not that a big of a deal. If you have an east and west facing panels, you'd definitely want at least two. BTW, if you have a lot of shade think about microinverters since you ruled out SolarEdge. Enphase has their own their own AC battery, but other vendor's batteries will work (e.g., Tesla) will work with it, or you can use an AC coupling solution.

 

[secondhandluck]

Hegdes and Svetz, thank you. I'm learning as I go here.
I didn't realize that the majority of the hybrid inverters required separate charge controllers; I assumed (ass-umed) that they were similar to string inverters and would allow direct connections to the solar array. I first looked at the Solaredge Storedge which is appears to be a true string/ hybrid inverter, that couples to the LG li battery, and assumed that most hybrids were set up this way. Last night after reading for hours I realized that different manufacturers have different hardware. I saw that the Schneider Conex needs their Conext MPPT controllers (150v 60A or 600v 80A) to work. SMA has the SunnyBoy Storage, which appears to let the string inverter handle the grid tie function, and it only handles the battery charge/ back up functions.
My array has 2 strings mounted on one barn roof face, and 1 string mounted above on another, so I need 2 MPPT at least. The Sol-Ark is a but more $$ than the others, but it does seem to do everything I want in one package. I have to look at the Schneider 80A charge controller again, to see if I can determine how many MPPT/ strings can be connected. This poses a related question, why don't manufacturers publish the # of MPPT and voltage limits per clearly?
As I have the system designed now, 3 strings of 8 panels wired in series. The high voltage limits my wire loss as the panels will be mounted 150' from the inverter.
Again, thanks. SD

 

[Hedges]

Sunny Boy Storage is an AC coupled battery inverter for use with select 400V Li batteries having a communication protocol it understand. It can perform peak-shaving and store PV production for later in the day, but it does not function as a battery backup system by itself. A separate transfer switch is required, e.g. the SMA ABU (automatic Backup Unit)

https://files.sma.de/downloads/SBSABU-DUS185117.pdf

Sunny Island is a 48V battery inverter with built-in transfer switch. It supports lead-acid and NiCd, also select Li with supported protocol. It is 120V (for US market) so either 120/240V transformer or else two inverters are required to get the 240V of grid-tie PV inverters it plays with. Alternatively, add a shunt for current measurement and you can use any brand PV to battery charge controller.

https://files.sma.de/downloads/SUNNYIS4548_6048US-DUS161422W.pdf

If you want both grid and generator input on Sunny Island you need an external transfer switch.

Multiple MPPT - need to check current limits as well. One string per MPPT should work fine with that particular Sunny Boy. I was considering using it and over-paneling, with two orientations. To fit all limits I was going to put two strings of 8, 327W panels into each MPPT (total about 15 kW PV). To do that I would need the two strings to have different orientations; each MPPT would get one SW facing string and one SE. Two strings of the same orientation would have Imp too high for one MPPT. Isc was OK, however.

Think about how much power you need and when. AC coupled SMA system lets you get battery inverter plus PV inverter watts added together, at least while battery and sun hold out. DC charge controller means only the battery inverter is available for all AC power draw. See how much continuous AC power it can provide at the ambient temperature you're going to have.

Batteries cost more than everything else. If you can use power as you make it and draw almost nothing at night, you can undersize the battery. A backup generator for occasional cloudy days is cheaper than batteries. If some loads can be controlled according to battery charge state, e.g. pump well water only when batteries are near fully charged, then batteries can be smaller.

With PV panels in the $0.25 to $0.35/watt range, over-paneling and wasting unused production can be the way to go, rather than right-sizing the system and using batteries to level it.

What is your price range? Shopping new eBay listings for Sunny Island, get two for $2500 each. Sunny Boy, one for $1500. I bought SunXtender AGM batteries, $5000 for 20 kWh (14 kWh usable at 70% DOD). Mine is grid-backup not entirely off-grid so I expect 10 year battery life with only occasional cycling.

To use a single Sunny Island with Sunny Boy you need a 120V/240V transformer.
Or have a single Sunny Island with two 80A charge controllers. That gives you two MPPT. Multiple PV strings in parallel so use a fuse per string.

 

[svetz]

...I didn't realize that the majority of the hybrid inverters required separate charge controllers

"All-in-One" systems (like Sol-Ark) have everything (e.g., the MPPT) built in. Some like Enphase's microinverters are small units that sit under the panel and make AC directly... it just needs to be plumbed into the house (i.e., the MPPT is built in) and therefore there are no "strings" (which elinates shade issues and makes scaling up later super easy).

... why don't manufacturers publish the # of MPPT and voltage limits per clearly?

If you can't find those on the datasheet run away from them.

If you do decide to go with a string inverter, these might help you out some:

• What does it mean to have solar panels in parallel and series?
• Figuring out how many panels in series and parallel based on your MPPT

 

[Ampster]

The StorEdge is a DC coupled battery so it is not analogous to other hybrids. The SolArk is a versatile system. The Outback Skybox is less expensive but you would need two of them for your capacity.

 

[secondhandluck]

After a lot more reading, I’m liking the Sol-Ark 8k a lot. The dual MPPT each support 2 500V strings each, and you can program it to use any size and type 48V battery bank.
Svetz: the link for series and parallel MPPT info cleared up a few things, thanks.

The downside: I’m not sure I can afford the So-Ark and batteries right now. Maybe, have to see how work goes as we creep out of the Covid19 shutdown. If I don’t do the Sol-Ark, I will run a SMA SunnyBoy7 and make sure the string/array design will work with the Sol-Ark, so I can upgrade later with minimal hassle.
Thanks. SD

 

[svetz]

...The downside: I’m not sure I can afford the Sol-Ark and batteries right now.

I believe the Sol-Ark will work without batteries as a grid-tied inverter, that allows you to add them later. But call and verify if it's not in the brochure.
One big upside to that is that battery prices are still falling. So holding off a year (or starting small) would probably save you a bit anyway.

 

[Ampster]

Yes, the two hybrids I am familiar with are the Sol Ark and Outback Skybox and the both can work without batteries.

 

[agarg]

Sunny Boy Storage is an AC coupled battery inverter for use with select 400V Li batteries having a communication protocol it understand. It can perform peak-shaving and store PV production for later in the day, but it does not function as a battery backup system by itself. A separate transfer switch is required, e.g. the SMA ABU (automatic Backup Unit)

https://files.sma.de/downloads/SBSABU-DUS185117.pdf

Sunny Island is a 48V battery inverter with built-in transfer switch. It supports lead-acid and NiCd, also select Li with supported protocol. It is 120V (for US market) so either 120/240V transformer or else two inverters are required to get the 240V of grid-tie PV inverters it plays with. Alternatively, add a shunt for current measurement and you can use any brand PV to battery charge controller.

https://files.sma.de/downloads/SUNNYIS4548_6048US-DUS161422W.pdf

If you want both grid and generator input on Sunny Island you need an external transfer switch.

Multiple MPPT - need to check current limits as well. One string per MPPT should work fine with that particular Sunny Boy. I was considering using it and over-paneling, with two orientations. To fit all limits I was going to put two strings of 8, 327W panels into each MPPT (total about 15 kW PV). To do that I would need the two strings to have different orientations; each MPPT would get one SW facing string and one SE. Two strings of the same orientation would have Imp too high for one MPPT. Isc was OK, however.

Think about how much power you need and when. AC coupled SMA system lets you get battery inverter plus PV inverter watts added together, at least while battery and sun hold out. DC charge controller means only the battery inverter is available for all AC power draw. See how much continuous AC power it can provide at the ambient temperature you're going to have.

Batteries cost more than everything else. If you can use power as you make it and draw almost nothing at night, you can undersize the battery. A backup generator for occasional cloudy days is cheaper than batteries. If some loads can be controlled according to battery charge state, e.g. pump well water only when batteries are near fully charged, then batteries can be smaller.

With PV panels in the $0.25 to $0.35/watt range, over-paneling and wasting unused production can be the way to go, rather than right-sizing the system and using batteries to level it.

What is your price range? Shopping new eBay listings for Sunny Island, get two for $2500 each. Sunny Boy, one for $1500. I bought SunXtender AGM batteries, $5000 for 20 kWh (14 kWh usable at 70% DOD). Mine is grid-backup not entirely off-grid so I expect 10 year battery life with only occasional cycling.

To use a single Sunny Island with Sunny Boy you need a 120V/240V transformer.
Or have a single Sunny Island with two 80A charge controllers. That gives you two MPPT. Multiple PV strings in parallel so use a use per string.

Wow. what a comprehensive response. I am just reading and learning. ... Little late to the party.