Running Sunnyboy SB4000TL-20

Off-grid systems are not connected to the electricity grid

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Running Sunnyboy SB4000TL-20

Postby technoware » 29.08.2015, 01:15


Just need some help, I will be grateful if you can give some advice please. I have SMA SB4000tl-20 inverter and 16 panels of 250Watts. Estimated output will be around 3500 Watts AC 220Volts 50Hz
In Pakistan, where I intend to install this inverter and solar panels, the tie grid system is not permitted. Therefore I want to isolate the solar system. I have got the password from SMA to convert in to off grid mode. I also have a UPS which is connected to a big lead acid battery, which can give power of around 1200 Watts. If I connect the output of that UPS into the input of this inverter, the inverter should start to produce power and will give output. Will this system work? What will happen if the battery is fully charged, I mean will the inverter keep on giving 3500 watts output and destroy the battery or the UPS or will the inverter only produce the power in watts which is being consumed?
Basically, I want to run the whole load during the day time without feeding the grid and do not want to rely on batteries and any other expensive equipment.
Or is there any circuit, which can be made easily and cheap, which takes most power from the inverter and any surplus required power can be pulled from the grid? Sorry, I do not know German Language :(

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Re: Running Sunnyboy SB4000TL-20

Postby Retrerni » 03.10.2015, 03:28

There is much more to do than just hook those two systems together.
Usually, the island inverter should be at least the same size than the PV inverter, so that the pv inverter could run at full load while the island inverter is e.g. only charging it's batterys from it.
Please tell us the exact manufactuerer and type of module you have. It might make much more sense to get an MPPT battery loading module for you and let the UPS do the rest. But using a UPS usually is not the same than an island inverter...
If you use a PV inverter and do an ac coupling as you suggestet, than you must set the PV inverter to do power limitation over frequency (so that it will derate it's output power when the frequency goes up to protect the island inverter from being overloaded.
What kinds of load do you want to connect, what load do they draw and how long do you want to power them?


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