There are several things that can cause battery post corrosion (fluffy deposits). If the deposits are only around the post, most likely, there is a gas leak (charging generates hydrogen gas) between the post and the battery housing. A good gob of Vaseline or dielectric grease under and on top of the battery terminal will act as a seal.
Second, despite what is "advertised", lead acid battery do NOT like to be continuously trickle charged/"maintained". It will shorten their life. If the battery is in storage, a few hours per day is adequate.
FYI - Two 6v golf cart batteries will likely cost less and last longer. Of course the would have to be wired in SERIES !
