And put something "fresh" in this topic.....
I broke down and bought a "battery tender" type devise - partly for my own convenience and partly to ease the worries of a certain Mod (who knows a lot about batteries and the proper care thereof)

I found this at Autozone for $26.99 and it seems to do about everything a person might want.
It says it automatically compensates for temperature and also senses if the battery is "sulfated" and attends to that.
Here is my battery setup, which I referenced in another post
I installed a master disconnct switch on top of the battery box to completely kill all 12v. power to the camper, while not in use.
As an added bonus, for reading this post, I'll throw in a couple of my favorite camping goodies
This is a Stanley tripod LED flashlight - which the legs fold up, so it can be held like a regular flashlight, too. I use it very frequently when dry camping...even using it for general lighting by just setting it on the table or countertop and pointing it up. It is so bright that the reflected light is plenty enough for me for general lighting. I liked it so much, I bought another one for use around the house. I seem to remember paying around $10-15 each and they are usually on sale during the Christmas season.
These can be bought at Walmart and beats the heck out of rubbing two sticks together! They are sawdust and wax "bricks" and, unless the wood is wet, I only need 1/2 "brick" to start the campfire. One box will last several seasons.