I have a small boat and the main deep cycle battery is located just under a "shelf" like thing near the transom that acts as a cover for the gas tank and battery. On one side, it is completely open (the bow facing side), but its essentially otherwise enclosed. The battery is held in place with a plastic battery tray that is secured to the deck, and the battery is held down with a nylon trap and a buckle clip.
In the past, I've always released the buckle clip, maneuvered the battery out of the tray (there's NOT much room to work with, so its quite a hassle) and out from under the shelf in order to charge it. Now, though, I'm thinking of getting an onboard charger that would have the leads attached to the battery permanently, and when returning home, I would leave the battery in place and just plug the charger into the AC outlet in my garage. I know that ventilation is generally important when charging a battery, but my question is - is it safe for me to leave the battery in its tray under the shelf while charging? Again, one side of the "compartment" the battery is in is completely open, but the "shelf" is directly over top of it (maybe two inches of clearance)..
I love the idea of the onboard charger that I would leave plugged in to charge the battery and then maintain it until next usage, but I don't want to do anything unsafe.