Best source of straightforward, but very detailed information I have found is:
One Key page is this:
http://www.solar-electric.com/deep_cycl ... ry_faq.htm
Which has really good info on the following topics:
You can also download a version of the above page as a PDF:What is a Battery?
Types of Batteries
Starting, Marine, or Deep Cycle?
Deep Cycle Battery as a Starting Battery?
What Batteries are made of
Industrial Batteries (fork lift type)
Battery Size Codes
Gel Cells (and why we don't like them)
AGM Batteries (and why we do like them)
Cycles vs Lifespan
Amp Hours - what are they?
Battery Charging (Here is where we get into the real meat)
Charge Controllers (for wind/solar)
Mini Factoids - Some small facts about batteries
There ia also some good battery information here: