We have a number of donated 6v and 12v batteries of various size, capacity and condition. These are a valuable source of offline power and temporary power storage. They are simple beasts but there is a lot to know about the various charging and discharging characteristics and techniques depending on your application.
When dealing with mains charging it's worth knowing about how this is done in the industry. This video of Dave taking us through the typical UPS configurations
EEVblog #504 - UPS Tutorial & Teardown http://www.youtube.com/watch?v=Fj7e3WGUKO8