Adding battery backup to existing PV system; inverter recommendation?

[apctjb]

Would like to add whole house battery backup to my existing system. I have 5KW on my house with an SMA grid tie inverter, and 6KW on my barn with a Growatt grid tie inverter. I plan on adding an additional 10KW of PV on my garage with hybrid inverter & battery to supply backup power during power outages to all three buildings. So I am looking for an AC coupled system where the hybrid inverter is able to disconnect from the grid during power outages supply power from battery, and throttle the existing grid tie inverters according to the system loads . Simple schematic below.

Curious to get recommendation's on what inverters to consider and gotchas' to look out for.

Note: connecting the existing PV arrays on house and barn directly to the hybrid inverter and eliminating the existing grid tie inverters is not an option. They are all going to have to work together.

 

[Hedges]

Sunny Island would be my first choice for AC coupling to Sunny Boy.
Which model Sunny Boy? couple different ways to make them work.

But your selection of battery inverter and battery should go hand in hand.

There are HF inverters like SolArk which also AC couple, but recommendations are:
1) Connect GT PV inverter to "Gen" input (so it can be shed by relay), not to loads output.
2) Have more DC coupled PV than AC coupled.

With Sunny Island, need to avoid draining battery to the point of shutdown, which requires a work-around for "black start". I use a load-shed relay to avoid that.
Sunny Island doesn't have peak shave and time shift features, which newer inverters probably do.

Midnight Rosie is new, supposed to support AC coupling soon if not already.

Schneider does support AC coupling, but some issues forum members see regarding when it decides to charge batteries from it.