SMA Sunny Boy capabilities

[bteigrob]

This could be a little bit of a long backstory, so skip to the number points if you want.

OK, so my solar story began in June 2021. We were just done building our new place and we installed panels above the garage and got a SMA Sunny Boy 7.7 installed. The country I live in does not recognize power fed into the grid. You can feed into the grid, but their meters turn forward, no matter the direction of the current, so you end up paying for your extra kW that you feed back. Not a good idea, especially given the price of hydro here. So the installer knew how to configure the SB to read for back feed and throttle down production to prevent any current back feeding. Very nice!

So after a year of usage, we have generated about 6,500 kW and purchased 5,000 kW from the grid. We were pretty happy with these results (remember, the Sunny Boy only makes power if we demand power and if the sun is out). Me and the wife have had to adjust our routine a bit to maximize the returns. Heavy power demands (e.g. laundry and AC) can only be run during they day.

Now we were looking at adding some storage for a couple of reasons:

1) Back up power for when grid is down
2) Supply intermittent power for when clouds pass overhead
3) Also provide power for the house in the evening (as much as the batteries can)

Is the Sunny Boy Storage a good option for this setup? Right now, if the house demands more than the Sunny Boy can supply, it easily just takes from the grid (in cases where the dryer and water heater are on), but can the SB and SBS be linked up where the SB will take what the SBS can supply, and if more is still needed, take from the grid? Can it be connected to the house so that power is always on, even if the grid goes down? I would be totally ok with large loads like dryer and water heater going down if the grid goes down, but can some circuits be always on, so they wouldn't even notice the grid down? Also, I would still need zero grid feed with all this because I still don't want to pay for my extra solar power that I would export to the grid.

I have asked my installer if this is possible. He is very familiar with the POCO policies on solar here (heads, power company wins; tails, solar user loses) and is looking into it to see if it can be done. I figured I would just ask the community here if this is a good idea. I hear rumors that the POCO will implement some sort of solar buy back program, but it won't be favorable. They will implement TOU rates (higher rates just outside the window of solar supply) and pay you pennies on the dollar for any power exported to the grid.

I know the forum is "DIY Solar Power Forum", but I am not very DIY. I can understand the logistics of it, but when it comes to actually wiring and configuring, I am best off if I contract that out. The SBS with BYD HV batteries has been mentioned in this forum before, but I understood that HV batteries were not a good option. Is this because of price? Or are they lacking performance?

Sorry again for the long winded post, if something needs more explanation, please let me know and I will do my best. Thanks again!

 

[Hedges]

Sunny Boy Storage uses a 400V battery. Actually, lower voltage battery with bidirectional converter. The battery price probably makes it uneconomical. Calculate expected cost per kWh over its cycle life, compare to utility rates.

Perhaps the premium is worthwhile for backup when grid is down. But your Sunny Boy also has "Secure Power", AC output from PV without grid. (Maybe only US model, producing 120Vrms, not rest of world model.)

I would recommend Sunny Island. It uses 48V lead-acid battery or a lithium battery with compatible BMS. (Possible to use without BMS communication as well.) Sunny Island has better surge current, and up to 4x can be connected together.

Sunny Boy Storage is especially for peak shaving, time shifting, storing power which would otherwise be curtailed for zero-export. A separate box is required for grid-backup operation.

Sunny Island doesn't do time shifting, at least not US model. New European model may or may not. It can connect/disconnect from grid and cycle its batteries.

 

[ArtDeco]

Hello. I am also considering a sunny boy with battery backup (in the Usa) to replace my 10 yo system that was destroyed in a fire.
Did you implement such a system yet?

 

[bteigrob]

No I have not implemented it yet. It looks like my seamless changeover is not possible yet because protecting the line men is the first priority. So SMA inverters have to power down with the grid is out, and power back up in island mode. So I haven't done anything just yet.

 

[Hedges]

It should be close to seamless. When grid is lost, relay opens and Sunny Island or Sunny Boy Storage forms island grid for house. How close depends on how sharply grid goes away; may be in brownout condition longer compared to a dropout (which equipment ought to ride through.)

Any UL listed (or equivalent outside US) equipment should be sufficient protection against backfeed into grid down, for lineman safety.
Separate requirement for newer NEC is Rapid Shutdown, a switch to segment PV array to low voltage individual panels, for fireman safety. There is also AC fed to house wiring by battery inverter. Grid AC, inverter AC, PV are three separate sources that might need to be shut off. A single switch would be ideal but I haven't seen that.

So the installer knew how to configure the SB to read for back feed and throttle down production to prevent any current back feeding. Very nice!

I'm not clear on how Sunny Boys are configured for zero export. It appears to be a 3rd party meter with current transformers measuring grid connection, and networked system using Speedwire (Ethernet) commanding Sunny Boy. Possibly even going through internet to a server somewhere. I would be interested in stand-alone control, fast enough to keep peak and not just average at zero or target value export, in the event NEM-3.0 does second by second measurement of import/export.

Can you give details on your zero-backfeed configuration? Maybe what boxes are installed and what wiring between them?

Can it be connected to the house so that power is always on, even if the grid goes down? I would be totally ok with large loads like dryer and water heater going down if the grid goes down, but can some circuits be always on, so they wouldn't even notice the grid down?

You can have Sunny Island with critical loads and Sunny Boys on its output, so others go down with the grid but selected ones stay powered. Same with Sunny Boy Storage and its external transfer switch.

Once this switching to island grid occurs, you could manually restore power to main panel by switching interlocked breakers, which enable closing a backfed "Generator" breaker if main breaker is opened, so critical loads panel now feeds main panel. If Sunny Island is fed from main panel, turn that breaker off so it doesn't see its own output as grid power restored.

You would manually manage loads such as dryer/heater/air conditioner to avoid excess power draw. Sunny Island has two SoC based relays. I use one to close a power relay, connecting/shedding entire house while keeping Sunny Boys on line. This avoids drained battery and need to do a black start. A second SoC based relay could interrupt HVAC thermostat or control another power relay to shed loads such as dryer. This way, even heavy loads can operate from PV/battery but only when plenty of power is available.

I haven't looked into what similar load management is available using Sunny Boy Storage.
I see info on networked systems, but can't find reference to control of appliances:

Store solar power and use it flexibly » Home | SMA Solar

Store solar power and use it flexibly ☀Maintain your solar energy supply—even when the sun is not shining ✓With SMA Energy Systems ►Discover more now.

www.sma-america.com

 

[ArtDeco]

Thanks for your quick response. I had two sunny boy inverters for years (no battery)and only had to use secure power once during a multiple day blackout. Definitely not seamless, took me all day to get it switched over to run my freezer and lights. Sounds like you have a good installer, a rare thing around here.

 

[Hedges]

If you can handle house wiring, you should be able to DIY and self-educate, skipping the installer.
You may be able to go with old models rather than newer, when replacing equipment installed under an earlier connection agreement.
Sometimes new old stock inverters are available. I got Sunny Boys for $0.10/W. You may find used ones even lower.
Sunny Islands have been on eBay for $2900 recently ($0.50/W)

 

[ArtDeco]

Thanks. In theory I can handle house wiring, but in practice I will pay an electrician b/c I don't trust my own work. Especially after my house burned down from an electrical fire, I am a bit gun shy.

BTW the fire had nothing to do with my solar system.

But using a used inverter sounds very doable...is there a best practice to tell if an inverter is still OK ? We salvaged 18 out of 24 panels from my roof that tested at 36v.

 

[Hedges]

eBay sellers generally say "working" or "for parts or repair", some "untested".
If not as described, then returnable.
Just hook up to panels and power (I've used a dryer cord to test them on 240V outlet) and see if they work.

 

[MrDan]

Sunny Island doesn't do time shifting, at least not US model. New European model may or may not. It can connect/disconnect from grid and cycle its batteries.

Hedges, do you know if the SMA Data Manager M could facilitate time shifting if used with the Sunny Islands?

 

[Hedges]

I don't know.
It has the connectivity to do so, but I haven't seen such details described:

https://files.sma.de/downloads/EDMM-10-DS-en-36.pdf

 

[MrDan]

I just noticed this, it’s kind of vague:

The Sunny Island can be operated in a time-controlled manner using a timer function (like a clock timer), supplying power at a planned point in time. This function must be activated by using the parameter "510.02 InvTmOpEna".

 

[Hedges]

I think that is programmed to sleep and wake up when the alarm sounds.
Something similar used if battery low, wake up when sun is likely to be shining.

Obviously what we'd like is to be able to program timed import/export from grid. Shouldn't be difficult, but don't think it is in firmware of these Sunny Islands. It likely is in Sunny Boy Storage and maybe the European SI 8.0H
Perhaps Data Manager supports that, maybe by changing target battery voltage. But I think we'd want to set a target discharge rate, not have it do maximum.

 

[ArtDeco]

I am still looking at a sunny boy storage inverter ... there are some 5k or 6k models shown on the net now ... maybe buy a half dozen more old 250w panels to add to my array .
No clue about using the battery backup so far, it seems to only charge via grid not via pv which seems wrong ?

 

[ArtDeco]

It appears that all the SMA inverters can be mounted outside. I am probably going to build a carport or ground mount over a patio rather than a full garage (due to lack of money mostly). It would be great to have the inverter and battery out of the house in a cabinet.

Temperatures here run from low teens to high nineties Fahrenheit And there is usually a (occasionally strong) wind from the west . Array faces south and gets heavy snow coverage least once or twice a year .

 

[Hedges]

US model Sunny Island 6048US is not rain proof because it has a breaker and SD card slot on the front.
Mine are outside but under an awning. I also taped a plastic cover over the front panel.
The rest can all be mounted outside.

Sunny Boy Storage, look up the list of compatible high voltage batteries, determine price and availability. It will only work with one of those.

It can charge by PV, be programmed to take power as part of zero-export, to shift times of export and import from grid.

For backup, you also need ABU, Automatic Backup Unit. That is an autotransformer and transfer switch.

Only one Sunny Boy Storage can be used in a backup system, at least for now. Surge capability 9kW.
(In comparison, up to 4x Sunny Island, 11kW each so up to 44kW surge.)

 

[ArtDeco]

If all it takes is a rainproof cabinet for a sunny island, thats pretty easy. I thought the sunny islands had to be in a climate controlled area. Apparently I am wrong again, and will recheck, maybe the batteries only need climate control...

 

[Hedges]

"Operating temperature range -25 °C … +60 °C / -13 °F … +140 °F"
Output power is derated at elevated temperature, but at least they document what it is.
Used with Sunny Boys, those take the load during the day when weather is hottest.

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

"Temperature range: operating / non-operating –25°C …+60°C / –40°C …+60°C"
Sunny Boy same range. I don't think it is even derated; if so, not by much.

https://files.sma.de/downloads/SBxx-US-DS-en-41.pdf

 

[ArtDeco]

I looked at the recommended battery for a sunny boy with storage. Looks like I'm looking for a sunny island instead.

 

[Calvin98]

I am also wondering how you can set a Sunny Boy to do 0 export to grid. How did your installer do it?
Maybe in the Sunny Explorer Settings -> System and Device Control -> Grid as below?


Will setting one of these to 0% make the SB not feed the grid at all?
There are probably several hundred settings you can change with the Explorer. I counted at least 70 just in this Device Control section.