Well, after rather a few years of abuse my storage batteries are showing their age, and I'm considering replacing the whole set up (I'm extremely frustrated with the list to port of the oem installation - two 27Ds placed high and outboard to port, along with everything else heavy, resulting in about 3 deg of "heel".)
Anyway, I'm doing research for best options, and learning a lot as I go. My priorities are driven less by cost than by convenience and longevity, and possibly height as I consider opening up under the quarter berth. I've preferred wet cells for their longevity, but they do require more maintenance and I've occasionally fallen down on that job.
What are you using? How do you like it?
What were they thinking when they put the batteries there???
I am currently using two Trojan T-105 6VDC golf cart batteries as my house bank. I am going to be adding two more, to give me 450 Amp-hours in the house bank. They are fairly decent performance at a fairly decent price. However, a single battery failure is more problematic than if I were using two 12VDC batteries, as currently, there is no redundancy.
What I would like to do is replace the entire bank with a set of four or five AGM batteries (http://www.batteriesplus.com/p-32636-wka12-80c/fr-werker-12v-80ah-agm-battery-with-female-m6-terminal.aspx?CJPID=1531824). AGM batteries are maintenance free and can be placed in more places, due to the lack of a liquid electrolyte. They also have a far higher charge acceptance rate than do wet cells, so can be recharged, at least during the bulk phase, much more quickly.
Amgine -
I was "gifted" a couple of AGM batteries from a boat I worked on this spring, and they have been working well, with no effort from me at all, for ~3-4 months so far.
As Dan points out, there are more mounting options for AGM's, and I do like the fact that they wouldn't be harmed if the boat rolled, and/or they were flooded with seawater.
The darn things are expensive, though, and the capacity is not as great as a wet cell battery IIRC.
Don Casey's "Sailboat Electrics Simplified" has a pretty good write-up on the differences and +/-'s of the various battery types.