Hey All,
 The thing about batteries on the concrete...just a wives tale...Comes from the early days of batteries...No disrespect fm63....Cool is better, slows the electrolysis down....Trickle charge will ensure a good battery however I leave the batteries in my boat fully charged and disconnected. They always work the following year. If it doesn't start in the spring, I would have had to replace them anyway.....and usually at the worst possible moment in the summer. Most boatyards in the Northeast do the same. They have too many batteries to store separately. Look at this link:
http://www.inct.net/~autotips/battmyth.htm
Also:  
http://www.inct.net/~autotips/battstor.htm