Generator Settings on the Sunny Island for Off-Grid Systems

From Anwar Mahmood (guest post) on September 30, 2016 in Category Service with 16 Comments

The SMA Sunny Island is a grid-forming battery inverter that can be used for the construction of stand-alone power supply systems. The Sunny Island inverters are capable of forming an AC grid, this sine wave can be used as an interface for PV inverters to synchronize and feed power into the system which is used for supplying loads and recharging batteries.

Off-grid systems can be designed for supplying the complete load, but in order to do so, maximum load and unfavorable weather conditions are to be considered. When designing under these circumstances, the necessary PV system and battery capacity becomes very large which can result in a significant investment.

For the purpose of keeping the system size smaller and therefore reducing the necessary investment, an external AC power source such as a diesel generator set can be used, so that the system can make use of it during periods in which available power is not sufficient for feeding the loads. The generator is also used to supply power to charge the batteries in the case the battery State of Charge (SOC) drops too low.

Here we will be discussing how a generator can be connected to the Sunny Island, the parameters and the settings available for the generator.


Download the white paper for free

Download the white paper for free

Generator and Wiring Requirements:

The generator used must be able to provide a stable grid; typical nominal values are 230V at 50Hz. For a three phase Sunny Island system, a three phase generator will be required. When wiring the generator connections, please ensure that the installation complies with local codes and regulations.

For more details regarding generator compatibility, please refer to the Sunny Island Generator – White Paper, which can be downloaded here.


Connecting the generator to a Single Phase System

The generator must be connected to the AC2 terminal block. In the wiring diagram below, the L, N, and PE are used. The NTT is not used here in the AC2 terminal for an off-grid system.

Circuitry Overview: Single System

Circuitry Overview: Single System


Connecting the generator to a Single Phase Single Cluster System

In a single phase operation with multiple Sunny Islands i.e. one, two or three phase setup, the generator connections need to be paralleled to the second and third Sunny Island in order to get power from the generator of approximately 11.5kW per Sunny Island. In single—phase single-cluster systems, the Sunny Island inverters must be of device type SI6.0H-11 or SI8.0H-11.

Circuitry Overview: Single-phase Single-cluster System

Circuitry Overview: Single-phase Single-cluster System


Connecting the generator to a Three Phase System

For the three phase setup, each phase is connected directly to the corresponding Sunny Island, where phase 1 is connected to the master unit, phase 2 is connected to slave 1 and phase 3 is connected to slave 2.

Circuitry Overview: Three-phase Single-cluster System

Circuitry Overview: Three-phase Single-cluster System


Generator Auto Start Function

The Sunny Island can request the generator to automatically use the built-in relay. To use this function, the generator must support the automatic startup functions. The two signal wires from the generator are connected directly to the built-in relay of the Sunny Island. An example of this wiring is given below.

Generator Auto Start Function 


Setup during commissioning

During the Quick Configuration process done through the Sunny Remote Control (SRC-20), the external source must be set to “Gen”.

The system at this stage should be operational without any further settings and will work based on the default parameters (generator nominal current greater than 16A or approximately 4KVA **). However, some useful settings can be used to fine tune the system.


Settings and Parameters for Installers and Expert Users:

Although the default settings should be enough to run the system, fine tuning the generator parameters will ensure that the system utilizes the generator more efficiently when required. The Sunny Island may need to be in standby mode while this process is being administered and Expert access will be required to access certain parameters. The following settings below can be used to fine tune the generator parameters:


  • Relay Settings

The relay 1 and 2 of the Sunny Island can be used for the generator request. Generally, relay 1 is used for the generator control, and the second relay can be used for the other features and controls such as load shedding functions etc.

By default the relay 1 in set to “AutoGn”.


  • #234 Gen Control

The settings of the generator can be found in ‘#234 Gen Control.’ The voltage and frequency operating range can be set under these settings. Current drawn from the generator is another major factor, by default the max generator current is set to 16A per Sunny Island. The value can be changed based on the generator rating up to 50A per Sunny Island inverter.

**If the generator’s nominal output current is less than 16A, this parameter must be changed to match the generator’s nominal current to prevent overloading the generator.

Generator warm up time can also be changed. By default it is set at 60s. Please check the generator’s manufacturer recommendations to adjust this timer if required.

One other important parameter is the generator reverse power. The generator manufacturer will provide the maximum reverse current that the generator can handle and the time it is able to withstand the reverse power. By default it is set to 100Watts for 30 sec.


  • #235 Gen Start

The setting under this menu determines the conditions to start/stop the generator by the Sunny Island.

The most common settings will be the SOC (State Of Charge) values for generator request. By default the lower SOC is 40% and the higher SOC is 80%. What it means is that the Sunny Island will call the generator by activating the relay once the SOC drops to 40%, and will start charging the batteries from the generator power. The cycle completes by stopping the generator once the SOC reaches 80%.

There is also an option for a time dependent generator request with different SOC values for a 24 hour period in this menu.

Another option is the load dependent generator request. This setting can be used to call the generator when the load consumption exceeds the power rating of the Sunny Island. Setting this feature will ensure that the system will be able to function normally even if there is some unexpected load in the system especially at night time.



Once all the settings and parameters are set, under menu #540, the option can be used to turn on the generator manually by setting the parameter to “Start”. Once the relay activates, the generator will start, and once it is able to form a stable grid, the Sunny Island will then be able to sync to it and start drawing power from the generator.
After the test is completed, the parameter must be set to “Auto” for the automatic generator request feature.



In situations when the PV output power is not sufficient to support the loads or there is a low SOC on the batteries, connecting the generator to the Sunny Island will ensure that the extra power is available to fulfill the consumption/demand. Fine tuning the generator will make the off-grid system more robust and will ensure a smooth transition to the generator grid when extra power is required.


4.00 avg. rating (80% score) - 13 votes

The Author

Anwar Mahmood (guest author)

Anwar is a Service Engineer at SMA Australia.


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  • avatar

    Muhammad Arok

    March 19, 2017 at 14:34

    Hi, I am Muhammad Arok. Our company is Carpediem Elektrikal Nusantara, from Indonesia. I would like to know how to integrate our Stirling Engine with three phase three wire system with Sunny Island with neutral side utilized. Do we need to have delta wye transformer to get the neutral connected to Sunny Island? Thanks and best regards

    Reply »
    • avatar

      Christian Höhle

      March 20, 2017 at 14:53

      Dear Muhammad,

      the SI produces a WYE 230V/400V grid. If the Stirling Engine do not have neutral and PE and you connect it to the AC1 as a grid tied energy source, you do not need any transformer. If this is a grid forming energy source, we would connect it to the AC2 entrance of the Sunny Island and we need the transformer.

      Sunny regards,

      Reply »
  • avatar

    Gene Maxwell

    March 2, 2017 at 15:52

    I have a 10Kva generator linked to a Sunny Island 8.0H. It automatically calls the generator – except late evening/overnight, when it allows the battery bank to discharge without calling for the generator. Is this related to the 233 Menu settings ? How can I ensure the system calls for the generator at any time of day ?


    Reply »
  • avatar


    January 12, 2017 at 20:39

    I want to add a generator to my grid-tied battery back up system. I have the SB3000TL-US-22, SI 6048, Midnite solar E-Panel & Midnite solar Autoformer. Can I add a generator to this setup? If so, Do I tie the generator power into the E-panel? The SI has only one AC1 and one AC2, so I don’t know haave I would tie the generator into the system.

    Reply »
    • avatar

      Shi Huan

      February 14, 2017 at 08:27


      I have two question for pass testing. For SOC control, Why is it not able to stop the generator when the cycle is met?

      Is it possible to have all three SOC, time and load control to be done together?

      Shi Huan

      Reply »
  • avatar

    Ockert van Schalkwyk

    January 10, 2017 at 13:08

    Hi. Like Manfred, I also want to know whether the generator input of the Sunny Island can be connected to the Mains Grid. In this setup, when the battery is low, the Sunny Island can fall back on mains electricity as a last resort.

    Reply »
  • avatar


    December 20, 2016 at 21:20

    We are just installing the Sunny Island 6.0H inverter on an off-grid solar system and would value any advice on recommended backup generator (make and capacity) which is known to work well with your system.
    Many thanks

    Reply »
  • avatar

    Brian J

    December 2, 2016 at 16:44

    My batteries are discarded just below 20%. I have a grid tied SB3000TL-US-22 and a SI6048. the LBM keeps coming on because the SOC is 19.9% and the Battery voltage is 41 volts. Can I change the SOC % some where below the 20%? If so, how would I do that?
    The batteries are NiFe were shipped to around 33 Volts (for the entire battery bank). I just need to get them charged and I believe SI will work normally. Please advise. Thank You.

    Reply »
  • avatar

    Alain Mugnier

    October 28, 2016 at 07:44

    Can you confirm as to whether SMA Off-Grid Configurator 400 software has been discontinued ?

    I seem to remember reading a while back that it was.

    Numerous problems when entering client data where reported but no further correspondence regarding the matters have been received.

    One being entering of custom generator data because common specs on the Kubota series for example is not in the default drop-down selection menus.

    Upon entering the data it would not save often it would just vanish the moment you changed tabs.

    Have such issues been patched as this proved most annoying for the amount paid ?

    Also license key authentication was a major setback.

    Reply »
  • avatar


    October 25, 2016 at 05:42

    Hi dear friend
    I need price about SUNNY BOY SMA SB 1.5-1VL-40, and why sale me this equipment in Argentina. On E-mail, please.
    Thank you very much

    Reply »
  • avatar


    October 17, 2016 at 03:56

    Good stuff. Keep it up 👍

    Reply »
  • avatar


    October 12, 2016 at 15:18

    Hi dear friend how are you.

    I was already on a subject related to the inverter by on grid but have no network connection correspondence.
    Your advice was:

    My question is:
    Is the solution offered on the site the inverter SUNNY BOY 2.5 and SUNNY BOY STORAGE 2.5 can be used to replace the inverters(SUNNY ISLAND and SUNNY BOY TL)?

    Reply »
    • avatar

      Annika Linke

      October 17, 2016 at 14:36

      Hi Ehsan,
      at this moment it is not possible to replace the Sunny Island System with Sunny Boy Storage 2.5 and Sunny Boy 2.5.
      The Sunny Island System has got special technical features wich you need for an off grid system. The two other inverters do not have this technical features.
      Regards, Annika

      Reply »
      • avatar

        Manfred Hinsch

        October 28, 2016 at 13:01

        In an “off-grid” installed sunny island & sunny boy, is it possible to use the grid to simulate a generator? i.e. Make the sunny island think that the grid is actually a generator and use the 234 / 235 parameters instead of the 233 parameters?
        Regards, Manfred

      • avatar

        Lucas Unbehaun

        October 31, 2016 at 11:02

        Hello Manfred,

        Please dial +49 561 9522-2499 to contact our service line directly. The colleagues over there will be happy to assist you.

        Kind regards, Lucas

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