Nish4

I have 2 x 5kW Sunsynk, initially I had 1 x 15kWh BSL...but that got hit by a lightning strike along with both inverters.
I now have 2 x 5kW Sunsynk inverters, with 2 x 10kWh Dyness batteries.

The system caters for 2 x households, so everything is x2 basically. 2 x geysers (3kw and 4kw), multiple TV's, fridges, washing machines, dishwasher network equipment, borehole pump, booster pump etc. everything except the 2 x ovens are on the system.

Zero issues experienced across both setups, with a single battery or multiple batteries. System just works.

Depending on your budget maybe aim for another 5kW inverter and more panels...

Am running 2x 5kW Sunsynks with 6x Pylontech - and am generally happy with my system.
Yes, I do have a small issue with my system in that my slave has a higher battery draw when the system is connected to the grid. But I would call it more annoyance than issue. I have raised it with Sunsynk and they want me to send in both inverters to be able to replicate the issue - and to me that has not been worth it. The issue only presents when connected to the grid, and I am manually disconnected from the grid 95% of the time - so it is not bothering me really.
Other than than, the system is rock solid and absolutely stable.
I would recommend 2x 5kW over 1x 8kW/10kW to get the additional MPPTs for greater flexibility as well as redundancy in case there is a fault on one inverter.
Batteries and both inverters connected to a common bus bar
From what I understand, it is best to split PV strings across both inverters - e.g., rather have 1 string on each inverter instead of 2 strings on a single inverter and nothing on the other
I would probably go with 1 battery and additional panels. I think you will otherwise struggle to get you batteries charged
Your sparky will need to check. But if you install a 2nd inverter, then your initial inverter connection should be fine

Thank you Carl, Ideally I would like to end up with a system like yours with total 20kWh batteries and additional panels (totally off grid). Looks like the additional 5kW inverter is making more sense. I know I will lose if I try and sell the 5kW inverter as second hand to purchase one single unit.