What is AC-Coupled Storage?
AC coupled storage is the connection of a battery energy storage system to a solar system via AC (alternating current) electricity. Energy from a solar system is generated in the form of DC (direct current) electricity which is then turned into AC by the solar inverter. A battery inverter connected to the same electrical network via AC then converts any spare energy not used by the home back into DC so it can be stored in a battery. By contrast DC coupled storage uses what is commonly referred to as a hybrid inverter, where both the solar and battery are connected to the same inverter. However, as we’ll see below there are many reasons why AC-coupled storage using high voltage (HV) batteries offers a number of advantages in terms of cost, flexibility and risk compared to DC coupling. - https://tinyurl.com/ycjxop4c

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Note added at 37 mins (2020-07-08 10:41:26 GMT)
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z instrukcji obsługi „inwerterów solarnych” Growatt


System inwertera działa jedynie, kiedy jest prawidłowo podłączony do prądu zmiennego w sieci energetycznej. - http://growatt.pl/wp-content/uploads/2020/01/Growatt-instruk... - z instu inwertery solarne