SMA Sunny boy 7.7

[Johneb]

I have the opportunity to purchase a Sunny Boy 7.7 for $700. It is a couple of years old. The upside is that I can run the whole house off of this one inverter no problem once I put panels in. The downside that I see is that to have energy storage I have to either purchase a very expensive specialized battery for it or purchase a Sunny Island and the then batteries. Both options are not cheap, maybe even about the same price. Question 1. Is this a good price and would you purchase it. Question 2. Are the batteries for this readily available at decent pricing or would I have to purchase a Sunny Island and batteries to be able to store energy? I know they are quality inverters I am just debating whether this is worth purchasing.

 

[OzSolar]

I have the opportunity to purchase a Sunny Boy 7.7 for $700. It is a couple of years old. The upside is that I can run the whole house off of this one inverter no problem once I put panels in. The downside that I see is that to have energy storage I have to either purchase a very expensive specialized battery for it or purchase a Sunny Island and the then batteries. Both options are not cheap, maybe even about the same price. Question 1. Is this a good price and would you purchase it. Question 2. Are the batteries for this readily available at decent pricing or would I have to purchase a Sunny Island and batteries to be able to store energy? I know they are quality inverters I am just debating whether this is worth purchasing.

Terrible deal. What's the guy's number? Just being silly.

So that inverter can be bought new for ~$1700 and the 10 year warranty still be fully intact. $700 is probably about right for a used one assuming it works. That's a great inverter for batteryless grid tied and if that's all you ever want to do then go for it.

IMHO you probably should first design the system that you want then look for components. I'd hate to lock myself into a system that cost a lot more money and/or might not do what I wanted because of good(ish) deal.

FYI, SMA support has gone from nearly worst in the industry to setting never before though unachievable records for being awful so we only spec them as a last result now a days. (stay away from SMA is what I'm trying to say)

 

[Johneb]

Thanx OzSolar. I'll try the design the system first idea.

 

[OzSolar]

Thanx OzSolar. I'll try the design the system first idea.

You were wise to ask.

 

[Hedges]

The downside that I see is that to have energy storage I have to either purchase a very expensive specialized battery for it or purchase a Sunny Island and the then batteries. Both options are not cheap, maybe even about the same price.

No battery is available for Sunny Boy 7.7

(expensive) Batteries are available for Sunny Boy Storage.
Sunny Island has a larger range of battery options.

Sunny Island should work well with Sunny Boy, but you would need two Sunny Island, or else a transformer and program 6.7kW limit on Sunny Boy (and you would likely exceed allowed PV breaker size in panel.)

Sunny Boy 7.7 should be good for a house with 200A main breaker. (40A breaker complies with 120% rule, carries 32A continuous through two poles at 240V)
$1/watt is a reasonable price.

You may have to put RSD boxes on your panels if they are mounted on the roof.
The Sunny Boy has "Secure Power", AC output direct from PV without batteries while grid is down (120V, 2000W). I think they have a kludge to make it work even if RSD is installed. (Everything will be simpler & better if you ground mount the panels instead.)

Design your whole system, including PV panels and any battery storage, before purchasing it.
Battery storage is usually an expensive luxury, so if you are doing this for the money consider no batteries.

 

[Johneb]

Thanks Hedges. We do have a 200 amp main. I think unless I am blessed with finding two Inexpensive sunny islands to work with it I am going to pass. Thanks for the advice.

 

[Hedges]

Sometimes 200A main breaker, but panel and busbars are rated 225A. That would allow 70A PV breaker.
When you install a battery backup system, that same 120% rule limits breaker size feeding your loads, even if PV is sized to not exceed 32A continuous.
More ideal is 200A main breaker at meter, and separate breaker panel. Then you can branch off 200A for your PV system and 200A for main panel.

If you want inexpensive, there are all in ones priced much less than Sunny Island + Sunny Boy. Look for something that supports split-phase natively; don't buy a European 220V model.

You can find Sunny Island on eBay for $2500 each. Not a bad price, but two of them would be best utilized with 13kW of GT PV for on-grid use or 24kW for off-grid.

If you don't build a battery backup system (batteries are the most expensive part), the Sunny Boy's "Secure Power" feature would be a convenient.
But an alternative is a batteries-optional all-in-one that could keep powering the fridge each day without manual intervention.

 

[Sanwizard]

Sometimes 200A main breaker, but panel and busbars are rated 225A. That would allow 70A PV breaker.
When you install a battery backup system, that same 120% rule limits breaker size feeding your loads, even if PV is sized to not exceed 32A continuous.
More ideal is 200A main breaker at meter, and separate breaker panel. Then you can branch off 200A for your PV system and 200A for main panel.

If you want inexpensive, there are all in ones priced much less than Sunny Island + Sunny Boy. Look for something that supports split-phase natively; don't buy a European 220V model.

You can find Sunny Island on eBay for $2500 each. Not a bad price, but two of them would be best utilized with 13kW of GT PV for on-grid use or 24kW for off-grid.

If you don't build a battery backup system (batteries are the most expensive part), the Sunny Boy's "Secure Power" feature would be a convenient.
But an alternative is a batteries-optional all-in-one that could keep powering the fridge each day without manual intervention.

Hey, Hedges, happy new year buddy! Quick question. I currently have two Sunny Boys connected directly to the main 225amp panel on my new (but real old) home backfeeding the grid via a single 240V 50 amp breaker in the main panel. I was just reading the Sunny Island manual, and on page 18, its showing the AC1 connection to the Sunny Boys and loads, and the AC2 connection to Gen amd Grid. Does this mean when using Sunny Islands, I need to move the sunny boys BEHIND the sunny islands, so the Islands are Grid tied, and the boys are in a micro grid with the islands?
I was hoping to use the sunny boys to charge the batteries on the sunny islands via the existing grid connection, as the boys have the PV connection, but it seems they cannot share the same main panel where the loads are. Is that right?
I am a newb at AC coupling. Any tips or drawings appreciated!

 

[Hedges]

A 2-pole 50A breaker on 120/240V split-phase service, at 80% continuous load, is sufficient for 9.6kW

A Sunny Island can pass up to 56A in either direction through its relay connecting AC1 and AC2.
A 70A thermal-magnetic breaker seems appropriate, with 6 awg or 4 awg wire (hot location 4 awg for 70A, although we never expect that much current.)
For some reason manual says max 56A breaker on AC1.

I'm now using 60A Midnight/CBI magnetic/hydraulic breaker, guaranteed no-trip below 63A. Also have Carlingtech 70A guaranteed no-trip below 70A.

If you connect SI AC2 to grid, battery will charge whenever grid is up. After a glitch following power failure it will supply AC1 from battery.

If you want PV to keep SI and its battery operating during an extended power failure, yes you want Sunny Boys on AC1 island side.
If you have 2x SI in a 120/240V system, 56A current limit means 13.4kW maximum PV for grid-tied. (Off-grid, up to twice SI rating so about 24kW).
If you had two SB 7.7, with enough PV to possibly exceed 13.4kW, I would suggest putting one behind SI and keeping other on main panel. Use manual interlocked breakers to feed main panel from SI during extended grid outage.

If using SB with SI, it should be set to UL-1741-SA (Rule-21), or "backup" with RS-485 interface for older models. "off-grid" works great, but is not correct and safe according to documentation (SI appears to provide utility worker protection because it performs anti-islanding and can isolate from grid, but relays can weld closed.)

Diagram:

https://files.sma.de/downloads/SI6048US-DS-en-28.pdf

An interlocked breaker panel for "load" is useful to bypass SI if it fails.
A load-shed relay is useful to disconnect excessive loads so SI keeps operating until sun comes up and SB can again produce.

 

[Sanwizard]

A 2-pole 50A breaker on 120/240V split-phase service, at 80% continuous load, is sufficient for 9.6kW

A Sunny Island can pass up to 56A in either direction through its relay connecting AC1 and AC2.
A 70A thermal-magnetic breaker seems appropriate, with 6 awg or 4 awg wire (hot location 4 awg for 70A, although we never expect that much current.)
For some reason manual says max 56A breaker on AC1.

I'm now using 60A Midnight/CBI magnetic/hydraulic breaker, guaranteed no-trip below 63A. Also have Carlingtech 70A guaranteed no-trip below 70A.

If you connect SI AC2 to grid, battery will charge whenever grid is up. After a glitch following power failure it will supply AC1 from battery.

If you want PV to keep SI and its battery operating during an extended power failure, yes you want Sunny Boys on AC1 island side.
If you have 2x SI in a 120/240V system, 56A current limit means 13.4kW maximum PV for grid-tied. (Off-grid, up to twice SI rating so about 24kW).
If you had two SB 7.7, with enough PV to possibly exceed 13.4kW, I would suggest putting one behind SI and keeping other on main panel. Use manual interlocked breakers to feed main panel from SI during extended grid outage.

If using SB with SI, it should be set to UL-1741-SA (Rule-21), or "backup" with RS-485 interface for older models. "off-grid" works great, but is not correct and safe according to documentation (SI appears to provide utility worker protection because it performs anti-islanding and can isolate from grid, but relays can weld closed.)

Diagram:

https://files.sma.de/downloads/SI6048US-DS-en-28.pdf

An interlocked breaker panel for "load" is useful to bypass SI if it fails.
A load-shed relay is useful to disconnect excessive loads so SI keeps operating until sun comes up and SB can again produce.

Awesome reply. Thank you!