I ended up with 200 Ah cause I was planning on using 1200 Ah for the main bank when I found the starting bank died. So I salvaged a few cells to replace a 4D with LiPO4 cells for about the same Ah. My gen set also starts from the same bank. While the Yanmar
starts instantly, the Northernlights gen set takes a bit of cranking.
The 200 Ah I installed takes about these same pace as the 195Ah AGM
it replaced. I had to move the Hitachi 55Amp alt off this bank cause it was trying to overcharge the bank. Now I have both the 100 Amp and 55 Amp alt on the house bank and connect the two banks with the switch while charing, only when the starting bank needs a boost.
My only caution with smaller banks, I had my internally regulated Hitachi overcharging my 200 Ah bank. You many have to adjust your alt if it is dedicated to the engine bank.