they can ring your bell continuously for 25 years or so

Nah ... those are tiny.

What you want are Exide OPzS flooded cells - available up to 2V @ 12,000Ah
I'm sure there are bigger on the market, but that's as big as I've worked
on.



Though I now work for a different industrial battery manufacturer...I used
to work for Exide...
but never worked with cells larger than 1700 AH. I think the largest cell I
could carry into my basement
would be about 300AH