Sunny Island Questions

cal23cal23 Registered Users Posts: 2

Sunny Island Questions.

 The goal is to be able to use the power that our 12kw array produces during the day when the power company has a wild fire emergency power shut off. Now, when the grid goes down the PV production stops.

 Looking to get a 2 Sunny Island system for 240V/60hz. Already have SB5.0US from 2013 and a SB7.7US from 2018 on 12kw array (6kw panels on each inverter- both produce 5kw max). SB's are 300 feet from where the SI's and battery will be. The SB5.0 is connected via RS485 to a Sunny Data Control PLUS. The SB7.7 is connected via 4 cables in a 4 pair (8 wire) shielded ehternet cable and switch to the LAN. SB 7.7 is accessed through Sunny Explorer software on the LAN. SB 5.0 is accessed through the SBC+ and on a computer and the Sunny Data Controll program. The RS485 cables ends about 40 away from where the SI's will be, but it is next to the LAN switch.


 Since the SI frequency shift starts at 61.5hz and ends at 62.0 hz, how do you tell the SB's to reduce power? Both of the SB's disconnect when they see a frequency > 60.5hz. I.e.they are already off when the SI tells them to reduce power when the battery is full and loads lower than PV production.


Does the SI master need to be connected to one or both inverters with a 300'+ ethernet cable and RS485 boards? (SI and SB's are 300' apart).


A SMA article talks about "Backup Mode parameter installed to the “On_all” setting" is on set to on by default as of 05-2014. So the 7.7 from 2018 have this on already? The 5.0US from 2013 needs to have it changed? How to change it? Where to change it?


The SI manual says the wires all need to be the same ga and length in parallel setups. What is the reason that wires need to be the same length exactly? How much leeway is there? +/- a few mm? cm? inches? feet? In a split phase 240V system the AC1 lines can be different lengths? i.e. master AC1 7' long, slave AC1 10' long (as an example)?


The SI manual also says you have to connect the master to L1 and slave to L2. How do you know which line is L1 and L2? is is a random assignment? L1 is always on the "left" side of the breaker and L2 is on the "right" side? Do you just connect the master to "one of the 2 HOT wires" and the slave to "the other hot wire"? with the voltage between the 2 HOT wires = 240V? I know that L1 and L2 are the 2 hot wires in the system that make the 240v, but I have never seen anything that specifically designates a connection to "L1" and "L2"


PG 69 of the manual describes the "External power supply" =

PvOnly, Gen, Grid, GenGrid. What does each parameter mean? What is the difference between  them? When would you want to set it for one or the others? For our system it would be one of the last 2 options?


The goal is to use the DC inverter(s) (Sunny Islands) to create the grid so that the Sunny Boys (7.7 & 5.0) can supply the big loads during the day when the grid is down. When the Sunny Boy's are producing power (about 20 amps max each, 40A total), we will turn on the big loads (water pumps, AC, etc) during the day and try to balance the consumption with the production as best as possible. The goal is to minimize, charge or avoid the use of the battery during the day. Then, at night, when the Sunny Boy's are not producing power, we will not run any of the big loads and just run normal small loads (fridge, lights, small water pump) that the battery can supply through the 2 Sunny Island inverters. If necessary, we can run a generator for some time at night or the day to charge the battery. The next morning, the Sunny Boy's can start by recharging the batteries and later, when there is more power available, we can start to run the big loads again.  Is this possible with what we have and 2 Sunny Islands?

Can the Sunny Island charge the battery at the same time as providing the rest of the AC power while the Sunny Boys provide power?

By the way, we are not looking to store 100% of the power we produce during a day when the grid is out either. We are looking to have just enough battery power to last the night with fridges, lights, etc. Of course the main objective it to be able to use the power we produce during the day when the grid is down.

Our Sunny Boys are about 300' away from where the DC inverters and battery will be. Does the Sunny Island need to communicate with the Sunny Boys? From reading the manual, it seems that the Sunny Island can regulate the power output of the SB's by just by changing the AC frequency (so no ethernet connection is needed). The SI's start to reduce power at 61? and at 62? hz the Sunny Boy's shut off entirely. Is that correct? At 61.5Hz, they will only put out 50% of their power, for example? It is not just a simple turning "on and off" of the Sunny Boys? Or put another way, the output of the Sunny Boys is infinitely adjustable by the Sunny island from 100%  to 0% by adjusting of the frequency between 61 and 62 hz?

Does the Sunny Island have some sort of program like the "Sunny Explorer" for the Sunny Boys? Can the Sunny Explorer communicate with the Sunny Islands via local ethernet or wireless connection? It seems like there is no ethernet or wireless connection on the Sunny Island.

If we have 2 Sunny Islands, do both charge 1 battery? Max current is 130A ?or (130A x2 inverters) = 260Amps?

Can you use a marine battery disconnect? (48V 300Amps) like a Perko switch? Do you  need to disconnect both the + and the - or is disconnecting 1 sufficient? Since the batteries are on a forklift (555Ah at 20 hr rate), they already have an Anderson plug where they can be connected and disconnected for charging, etc. Can the Anderson plug be the battery disconnect?

What size fuse would you need for this?

I was reading that the SI adjusts the SB's power by adjusting the frequency. It starts lowering the output at 60.5hz and at 61 it shuts the inverter(s) off. Now I was looking in the SB7.7 and 5.0 manuals and they actually shut off when the grid frequency is 60.5hz.

I also read:

where is says that newer inverters have the "Backup Mode parameter installed to the “On_all” setting."

So the 7.7 we got last year should have this on already? How do you change it in the SB 5.0US that we have? I have not seen anything in either manual that discusses it.

Lots of questions. Trying to see if the SI’s we do what we want.


  • bill von novakbill von novak Solar Expert Posts: 891 ✭✭✭✭
    As far as I know, the SMAs will not allow linear control by changing frequency.  For that to work you need Sunny Boy microinverters.  You would have to do a "conventional" AC coupled system, which will disconnect one or both SMA inverters when the Sunny Island batteries are close to fully charged.  Note that the power rating of the Sunny Island must be significantly higher than the power rating of any inverter you have on the system.
  • cal23cal23 Registered Users Posts: 2
    Pg 127 of the SI manual says:
    "If the battery is fully charged, the frequency limits the power output of the AC feed‑in generators
    (Sunny Boy). If the generator is now manually started, for example, the frequency would be lowered,
    if required, as the Sunny Island synchronizes with the generator. The AC feeding‑in generators (Sunny
    Boys) would then feed additional energy into the system and possibly overload the batteries. In order
    to prevent this, in this case the stand‑alone grid frequency is temporarily increased, in line with the
    synchronization, until the AC feed‑in generators (Sunny Boy) are disconnected from the stand‑alone
    grid system as a result of the grid limits being exceeded."

    Pg 151 also describes it.
    "To prevent the excess energy from overcharging the battery, the Sunny Island 4548-US/6048-US
    recognizes this situation and changes the frequency at the AC output. This frequency adjustment is
    analyzed by the Sunny Boy. As soon as the power frequency increases beyond the value specified
    by "fAC Start Delta" the Sunny Boy limits its power accordingly."

    One of the issues is that the FSPC (Frequency Shift Power Control) starts at 61 hz and the SB will shut off at 60.5 hz as I understand it.

    Somehow you have to set the SB's so they do not shut off when the hz is >60.5 when the grid is down.

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