I have a big very heavy Sears Marine deep cycle 12 volt battery (like
the kind used in motorhomes and such like) I bought at the local Sears
store about six years ago.Those kinds of batteries (deep cycle
batteries) shouldn't be drawn down to more than about half capacity,or
so I once read in an article.With proper care and maintnance,deep cycle
marine grade batteries should last ten to twelve years or more.
cuhulin