Keeping batteries healthy over winter - how?

I have recently bought a 2005 Abbey GTS but was told that the battery was worn out (I am sure that this was a genuine wear and tear matter).  I want to get another battery but apart from having to move the van a few times with the power mover while the drive is tarmaced, it is unlikely to be used until early spring.  I can't move it without the mover so what is the best way to keep a new battery healthy when not in use?

Many thanks

Paul