Because solar energy is variable in its input parameters (clouds, night, etc), your batteries will probably not be topped off constantly.  There are systems out there that convert 120-volt AC power to the lower voltage DC power your batteries want; this lets you bank power from your utility company for later use, and helps cut down on the wear and tear of your battery array, and can even recondition some types of batteries.  When looking at battery chargers, talk to the manufacturer of the batteries you're using for their recommendations on charging voltage.