
Whatever you get, make sure it is a Sealed AGM design. If it comes with acid it isn't AGM. AGM, Absorbed Glass Mat. The acid on these batteries is injected under vacuum so that only a certain amount of acid goes in the battery. It is then sealed.
AGM batteries can be deep cycled, charge 50% faster than flooded wet cell bateries and are much more resistant to vibration.
Here is the link for more reading. Good Luck!!
http://www.thesamba.com/vw/forum/viewto ... ht=battery