Battery 1 is connected to the motor and the mounted charger.
Battery 2 is connected to cabin items and the mounted charger
I'm wondering if I use the suggestion of getting a solar panel with a regulator then attach the regulator to the female end of a two outlet extension cord(cut) and then two male ends, one to each battery I can just plug in one or both batteries as needed. Simple that when one is plugged in not worries. But can I plug in both batteries at the same time with out damage.
I believe a good charger will isolate both batteries and charge both when plugged in. Kind of like 2 chargers in one unit.
Do NOT use a male plug on the batteries. The two posts could short or touch something and short and cause a problem. They should also be fused close to the battery no matter what.
The other danger with household plugs is confusion and someone plugging them into AC power. If you do this, label them big and obvious. (12V ONLY!!!!) and use female to the battery.
The motor should keep the starter battery topped off. There is little drain starting and 5-15 minutes of run time should replenish what it takes to start. I would let the motor handle keeping that battery charged.
It's your house battery that has most draining loads (Radio, lights, pumps, fridge). This is where the solar panel comes in.
IF your starting battery is going down, something is wrong. It's either time to replace or something is connected and draining it (maybe your battery charger isn't isolating batteries). Starting batt should not ever go down unless you haven't run your motor in months (6+)
I've been running 2 batteries for 8 years. 1) Starting 1) House and have never had the starter battery go down. I do keep a small jumper pack on board for emergencies, but have never used it.
If you charge (via solar panel) the house battery, your battery will charge unattended when away. I have this combiner that when the house battery is at 13.8V (charging) will combine the starting batt and charge it. Conversely, when the starting batt is at 13.8 (charging from motor) it will combine and charge the house batt.
http://www.defender.com/product3.jsp?pa ... &id=750182
As Willy stated, combining is not ideal full time, but it is foolproof. My last boat had an AB/both switch that I often left in the wrong position. The combiner is brainless. It just works.
If my house batt drains, I always have a starting battery.
When motor is running, it will combine and charge both.
When solar is charging, it will combine and charge both.
When idle, batteries are isolated.