here is an article by Nigel Calder, who is without a doubt the best writer on yacht systems alive on the planet, has written this intro on the newest AGM technology from the original developer of absorbed glass mat batteries.
Odyssey. The 4 page piece is titled 'Charging Into the Future.'
google> Charging into the Future
sailmagazine.com/boatworks/.../charging_into_the_future/ -
http://74.125.155.132/search?q=cache...J:sailmagazine....
[Did not type in what reproduces here in blue...]
These essentially drycell batteries sound fabulous.
A Group 31 (75#) will set you back a paltry $300. BUT........