Desert Steve wrote:
I leave the shore power connected and the charger switch 'on' when I am away from the boat but turn the battery switch to 'off'. Battery 1 is still very low when I return - it does not have enough charge to turn over the motor. I turned the switch to battery 2 and started the motor. I left the switch on battery 2 when running the motor. After some time running the motor with the switch in the battery 2 position, I turned off the motor and turned the switch to position 1 and the battery did not have sufficient charge to turn the motor so I turned the switch to position 2 and started the motor.
The black wire from the charger (a Guest brand) goes directly to the terminal on the battery, and the two batteries are connected by a jumper wire. However, the red wires appear to go the terminals on the battery switch. It seems to me that the batteries will not be charged if the battery switch is in the 'off' position. However, I confess to not being a genius when it comes to 12 volt electricity.
Ok, two things come to mind. The alternator charging the batteries is different than the AC charger. I believe the battery switch only affects how the alternator charges the batteries. I believe the AC charger is separate and is not affected by the switch. I could be wrong.
It's typical to have the negative side of the batteries wired together. This is usually the black colored wire. The red wires (positive) are not.
It's also possible for a battery to be bad. Either through defect, normal wear or improper charging. If the batteries have it, pop open the lids and check their water levels. If they get too low they won't work. They can get too low from over charging them.
It's possible for a charger to be defective too, the first one in my 348 cooked all three batteries but that was before I took delivery of it. I believe it was a Guest unit and they replaced it with a Charles. Not saying one brand is any better or worse though. Just that it's possible for one to be bad.
And it's also possible for the wiring to be bad. Usually due to corroded or loose terminals. Sometimes it's possible for a wire itself to be bad due to corrosion getting into it. Start by removing the wires from the battery terminals (using great care to avoid shorting anything), clean up the contacts and reattach them. Check that all the wires are clean and tight, this includes the ones going up to the alternators, starters and charger.
Oh, and some boats (typically two engine ones) come with a cross-over sort of switch that allows combining the batteries for starting. This allows tying both batteries together to get either engine started. It's usually a switch on the helm and it only operates in a push-button momentary fashion (as in, you have to hold it pressed).