pimpackukas

This is exactly what I have done with some other inverters:
It works well and is the best solution in my opinion. It disconnects AC Input to inverter so no chance of some kind of backfeed, and allows RCD to be used at output of inverter. Just remember that the N-G bond on the output needs to be before the output RCD (if you choose to install one on the output).

Since its LiFePO4, I'd say don't worry, but if you *really* want a lower SOC and treat the battery with kid gloves, then don't use inverter to batttery comms, set up the battery as user defined and since I'm guessing its a 16S battery, let's then set the bulk and absorbption Voltages to 3.45V, instead of the presumably 3.6V per cell. Thus 16 X 3.45V for bulk and absorption, which is 55.2V this will not quite get you to the 80% you're looking for, with LiFePO4's, I think it may be next to impossible to get there, unless you have a BMS which does coulomb counting and will let you, based on this count, limit the charge into the cells...

set the bulk and absorbption Voltages to 3.45V, instead of the presumably 3.6V per cell. Thus 16 X 3.45V for bulk and absorption, which is 55.2V this will not quite get you to the 80% you're looking for, with LiFePO4's, I think it may be next to impossible to get there, unless you have a BMS which does coulomb counting and will let you, based on this count, limit the charge into the cells...
3.45V will still get you to 100% it will just take longer. The problem is balancing might not take place depending on the BMS fitted.

When? off solar? I don't think you can limit the solar charge to battery when excess solar is available... if your battery is LiFePO4 chemistry, then you should not worry too much, if you are using Cobalt base NMC Lithium or NCA Lithium, then the only suggestion I'd have is to set the battery to user defined and lower the Voltages and thus the SOC % level...