I currently have a 3 bank that needs to be replaced. I cant decide if i want a 4 bank so the cranking battery can stay topped off or just get another 3 bank.

What do you use?

4 bank and glad I have a four instead of a three.  Keeps the cranking battery topped off.

All of your accessories (lights, pumps, electronics, radio, blender, etc.) will run off your starting battery. You absolutely, positively need a bank for all four batteries IMHO.

4 bank .....

thanks guys.

looks like i'll dig a little deeper and get the 4 bank.

For about 60 you can get a Combiner100 to connect between the starting battery and a house battery that is on the charger.  That way the starting battery will get topped off with the existing charger.

You have the added benefit that when the engine is running the alternator will maintain charge on the house battery since the Combiner100 is bi-directional