I store the boat at the river, about a four hour drive. I always bring the batteries home. The heat out there in the summer can be well over 110 degrees for many, many days. A real battery killer.
The way my storage yard works is I drive through the gate and drop it. Steve - who runs the yard - will come along at some point and put her away. So solar doesn't work for me since the boat could be put inside any one of a number of buildings.
It's become reflex now so it's no big deal. I've been able to maximize the life of my batteries compared to my friends who also store their boats there. One of them has gone through numerous batteries over the same time for various reasons. Neglect is the most obvious.
I always check the battery with a hydrometer and a load tester about a week or so before we go out just in case age has reared it's ugly head and I need to buy a new one.
Between the boat, the toyhauler (two banks, 4 batteries) 5 cars and trucks, 4 motorcycles w/batteries and the RZR, I have a lot of batteries to look after.
I did forget to bring the battery out once (maybe twice) and Steve just gives me one. So I'm always covered.
So, if you plan on leaving your battery in the boat, make sure you take the time to charge it fully before you put it away. You might consider adding a Priority Start disconnect switch:
http://www.batterystuff.com/battery-products/PS12VMarine.html so you don't get caught with a dead battery and no way to get the boat started.
ON/Off switches only work when you remember to use them. On/Off/All or multi-position switches should be avoided in my opinion. We call them idiot switches because you end up calling yourself that for forgetting which battery you drained or you drained all instead of one, etc. I prefer On/Off for each bank or battery.
Ideally you want it on a smart charger that will recharge it and go to a float stage and maintain it. If going solar, use a controller as David mentioned.
If you are going to add a bitchin' stereo and amps and lights and other cool stuff then you will need a bigger battery and perhaps a second, third, etc. depending on your set-up. Don't throw good money after bad by leaving a good charger out of the equation.
*all the above is just this guys opinion. What I do works for me. What you do hits your wallet, not mine.
