In addition to Calder's Boatowner's Manual, the Ample Power Primer (www.amplepower.com) [click on Technical Documents] and Jack Rabbit Marine (make it one word between www & .com), I have come across the following link to very good information about battery maintenance:
http://www.batteryfaq.org/index.htm
Just click on the "FAQ 5.2" hyperlink below the battery picture to get to the juicy text.