Originally Posted by Many Hats
Too many responses about adding other components, but like the OP, Iím about to install a 100w panel and controller on my ďNew to MeĒ boat. It has 2 batteries and a 1-B-2-Off switch.
I will look at the wiring tomorrow, but if the leads are split to 1&2, should I connect to just 1 battery or (+) of one and (-) of the other, and how would I charge both?
Well..... The 'official' answer is that with one (presumably single-bank) charge controller, one panel and two banks there is no 'proper' way to charge both banks at the same time. However, assuming one of those banks is a starting bank and the other is for house loads it's perfectly doable. Wire your controller to the house bankand charge it exclusively most of the time. Do you have a multimeter? Or even a panel voltage display? Every now and then, once your house bank is fully charged, parallel the banks (turn the switch to 'all') and monitor
the voltage on the starting bank. Once it reaches absorption voltage let it sit there for about four hours and then switch back to house only. It's not perfect but it will work
without having to buy any more stuff. The house bank should be heavy-duty enough that it won't suffer from the slight overcharge and the starting bank will stay topped up.
Of course, if you want to buy all sorts of new stuff there are many, many different options. :-)