Let’s assume we have a fully operational, 3-phase ESS with 3x multiplus II 48/10000 (system 1). System is Up and running and charged by 2x smart mppt rs 450/200.
Now let’s assume one wants to Set Up a second ESS (system 2), still connected to the grid however.
Here comes the clue: the second ESS shall be ‘charged’ by the excess Power of system 1, using the multiplus II AC-OUT 2, configured If system 1 SoC > 90%, send whatever is left from the MPPT RS to AC Out 2.
According to my Research system 2 could use a Quattro and have AC Out 2 from system 1 connected to AC IN 1. System 2 needs to be fully functional (from grid) even If system 1 fails (i.e. AC Out 2 deactivated).
The systems shall intentionally Not ‘know of each other’ besides the fact system 1 sees a Power consumer in AC Out 2 and system 2 sees some variable Power source on AC IN 1.
Can we do this? Has anyone ever done Something Like this before?
Yes. We have a customer that has two buildings on his property, each serviced by its own utility connection. The rear building has 4 Quattro 48/5000 120V inverters in parallel/split-phase, three MPPT 450/200, a bunch of Pytes batteries, and about 16kWp PV.
The front building is the same but with fewer batteries. There is no suitable ground space in the front for PV. The front is first serviced by excess power from the rear building and if necessary, turns on the utility input if the batteries get too low. This is rare. The farmer will likely disconnect the utility from the front.
This is in the USA so pardon me while I use our stupid imperial measurements
The two buildings have a three conductor 2AWG cable running 400 feet between the two buildings. Also in that trench was some old CAT5 cabling the farmer dropped in there two decades ago when we he built the rear barn.
Victron does not provide grid codes for the USA and so ESS can’t be (legally) used here. It really sucks. But, since he had the CAT5 in the ground we used it along with relays and assistants in the front & back to control ignore AC where needed to make this happen.
Another approach could be to use NodeRed if you have a reliable network connection between both installations.
