Agree with Matt. Check the batteries, look inside the cells, fill any that are low with distilled water.
Buy a meter. You can get a decent digital volt ohm meter at any hardware store or home center for less than 30 dollars, worth every penny.
Clean out your battery bay. nothing to lose, right?
sprinkle baking soda all over the batteries and the place they sit (if you feel really adventurous, pull all the batteries first. take pictures before you disconnect anything to make sure you can get it all hooked back up, it's really not a bad project. Baking soda followed by a good hosing will have your batteries and battery bay looking like new.
While you are in there, clean all the connections. use a small wire brush, and get everything clean and shiny.