Stephen Trapani wrote:
So my AC charger is a West Marine 5 amp. Alternator is a 60a which puts
out 35a. I (will) have two 6V T105s in series on BANK2 and a Kirkland
900cca starting battery on BANK1. I connect both charging sources to
BANK2 either on the battery switcher BANK2 post or right on the BANK2
batteries.

Remember that there is a connection between the alternator and the
starting motor on your Yanmar (I assuming that's what you have - I
don't know why). I'm guessing you want the alternator only on bank 2
and the starter only on bank 1.


I can charge both banks at the same time by putting the switch on BOTH
and don't have to worry about the starting battery getting overcharged
because even if it is mostly charged and BANK2 is almost dead, both
banks will only get what charge they need on the BOTH setting?

It could overcharge, but probably won't be that bad except in extreme
cases. The worst case is that your cheap Kirkland will only last 2 or
3 years. If you want to prevent this, you have to invest in something
like an EchoCharge, which is idiot proof, or figure out a fancier
switch setup, and remember to always do it right. When I was using a
combiner (which essentially sets it to "Both" when charging) the
starter bats still lasted 4 or 5 years. When I replaced them with
AGMs I added the EchoCharge.

Actually, your bigger problem may be that the stock Yanmar (Hitachi)
alternator won't do a great job of charging the house bank, so it
could end up chronically undercharged. I wouldn't worry now, but its
something to watch when you have it running.