multiple inverter and battery bank system

[daklein]

        Anyone running a system with multiple battery banks and / or inverters, coordinated together somehow?  See below for my crazy ideas.

        I have been setting up the components from a DC solar trailer (2x SMA SI6048 and 1080Ah forklift FLA @ 48v) in the garage as a battery backup and grid defection system.  Net metering is going away for our existing GT solar system, and I'll use keep most power on site.  Just about complete, still doing some wiring in the house to move circuits over behind the SMA inverters.   many pictures:     https://photos.app.goo.gl/q1euFhioH266nPvW9
        I can generally run the house continuously on a normal sunny day basis, the battery bank generally moves between 80-95%.   The additional solar from the trailer and previous microinverter rooftop solar is plenty even on cloudy days.  On a sunny day, running the house AC is fine, the microinverter output goes straight to the loads, still a little to float the FLA even.  On a sunny day, it can also charge our Leaf at 4kw, and have a little left to charge the house FLA.   All that, still staying above 80% SOC. 

         The issue is maybe obvious, it's not always sunny.  Need to be able to go a few days, and still don't want to take the FLA below 80%.   The kwhr used for the house loads is on the order of 10-20 kwhr each day.      The 1080Ah FLA @ 48v, at the generally low discharge rate it's used at, is on the order of 62 kwhr, but you want to only use the top 10-20% of that.
         Another concern is energy lost to charging the FLA in the top SOC range, that's where it loses the most energy in charging, gassing & bubbling.
        These both lead to lithium, pun intended.   Lithium is happy to have a wider SOC range, and is happier when not full.    I would like to have the FLA to handle the large power surges for the inverters, but keep them basically floating all the time without much energy throughput.   Let the lithium bank supply the average load over time, generally just 200-1000 watts.

        I have a 24 kwhr Leaf pack in great condition to be turned into an ~48v bank, and I have piles of working but lower output enphase microinverters.   About 20 m210s handle up to 58v DC input, with output of 140-180watts each   I'm thinking about using the microinverters to discharge the Leaf bank, turning on individual microinverters to match the recent average load, via relays on each micro, run by some tbd diy control.   The control could talk with the SMAs on CAN, or surmise the present target voltage of the FLA pack by watching for the AC frequency adjustment, and watching the FLA pack shunt voltage.   The microinverters would be AC coupled behind the SMAs, and their output would go straight to house loads, should be efficient.
        To charge the lithium pack,  I could use one or several 48v dcdc converters from the FLA / SMA 48v bus to the lithium pack.   Obviously a BMS, and a system controller to run the dcdc converter.     I may also add another PV array with a Classic CC to the lithium.   When the sun is out, the existing arrays put out ~6 kw on AC, so I'll want to take most of that via AC to the lithium.   The SMAs already have plenty of capacity (and efficiency) to take that to DC @48v.
        There are a couple of loads in the house that I will automate first, to use more available AC, instead of letting the SMAs throttle down the microinverters; the EV charger, heat pump water heater.

        My wife wants a big red Scram button on all of it too.

        So how's that for crazy?  Any better or worse ideas?  Thanks!!