I am trying to find out whether it is possible to add additional batteries to this system, can anyone help please?
All In One - GIV-A10-AC-13.5 kWH
As I understand things you can Parallel AIO's together.
Not sure if that feature is working yet as it is labelled as "Coming soon" (so probably 2025).

Not quite 2025, but parallel AIO will give you double power and double capacity
TheDragon (GivEnergy) doesn’t really answer the question about whether additional batteries can be added.

There’s a space in the gateway - 2 large terminal blocks - for the parallel connection.
How that actually works with another potential 5x AIO is unknown. Presumably there’s some magic self limiting & protection involved as setting all 6 on charge is 36kW of demand.
Tim no, additional batteries can't be added.
But you can* add another AIO (so another inverter and battery - technically four battery trays inside I believe, so many batteries!).
( * ) in the near future. Maybe 2024.
In the data sheet it states 18.4 kW so I would guess at 3 direct and 3 more daisychained as dumb batteries from the first 3.
But that’s the end game not the now.

kram I think that's because the house load breaker in the gateway is 80A / 18.4kW.
I don't think there is a second power outlet on the AIO itself for any chaining locally (although I don't have one so only what I've seen from snippets) nor any exposed battery terminals to do it that way.
I think I guessed previously that to chain them you'd probably bring the extra ones into their own seperate distribution board first and then take a supply from that to the parallel connection in the gateway. Can't see how else you'd bring 5 more sets of cables in realistically.
@hoggy Aye, a banks of 3/6 batteries with their own breakers in a DP which then connects into the gateway would make sense.
Sorry for the potentially stupid question but does this mean a 2xAIO install will be able to provide 12kW peak output as well as doubling the battery capacity? If so that's pretty cool as it would presumably allow an EV charger to be inverter side rather than grid side.

DJBenson That is the plan, upto 6 Max.
TheDragon (GivEnergy) I really wish you had a more concrete answer on when this is likely to happen - I'm having my AIO installed in the next few weeks and I really want two installing but I'm reluctant to do it in case the parallel feature never materialises which means additional cost for a return visit to install a second AIO 🙁