well, i'm not an expert in battery backup systems, and i'm of the opinion that any serious setup actually only uses them to stay up until the diesel generators (2+) kick in to maintain power because the whole density and safety problem is solved with diesel

so probably, my guess is, these days with a diesel genny and a small Li battery bank you got it sorted

i think the subject though is about people with solar/wind/battery based setups and not mains connected?

no, i looked back, it's just for coping with up to a day of bullshit from the mains provider

diesel generator is the main thing, the batteries are just there to keep it live until the generator gets to the needed voltage