My newly purchased boat has 5 batteries; (4) T105's and (1) 12v starting battery. The T105's are broken out into two banks on a 1/2/both switch and the starting battery is on its own on/off switch.

After readling the Link 2000 discussion below I realize I need some sort of battery monitoring system as all that exists now is a simple analog volt meter on the electrical panel. My question is why would the house batteries be broken into two banks? I don't see any specific reason for this. Any thoughts?

Thanks,