I found a good deal on used lithium batteries. They are Valence 137 ah that are said to have 300 cycles on them. I found them on Ebay. I bought 12 for 5040.00 . I did a lot of reading and they are very high end with nothing but high end parts on them. I chose 2 at random charged each full with bench charger. Then drained each , one at a time with an inverter with a amp clamp on meter and timed the discharge till the low voltage shut off stopped the discharge . The tests both showed 132.5 ah. So that comes to 1590 ah battery bank. Do your checking . There are videos and speck sheets on line.