I have a 2 bank system in my NA23 with 2 OPTIMA Blue Top Deep Cycle D31M batteries. I just redid this battery setup cause I had to move it over to to Port side of the boat. It was on the same side as the engine & the boat was leaning just a bit low on the starboard side as a result. This made it difficult to load on to the trailer at the ramp cause the keel was way over to the port side underwater. It ended up on top of the guide rails of the trailer a few times till I figured out what was happening. Duhhh
If your going to have only one bank, I have a three stage sealed charger for sale for $60. that I was using with my old system, it works great. It's worth $120 new.