Potterton EP2000 Battery?

Hi, My rather old Potterton EP2000 heating programmer seems to be playing up. The fuse has blown twice, located near the box, not the main fuse. I have noticed that the internal battery of the control box has leaked and is now defunct. Would the battery being of no use cause the fuse to blow? I thought the battery was only for backup in case of powercuts etc. Or do I need to buy a new frontage namely the Potterton EP2002 which I believe just pops over the wiring where the old frontage was.

Any help would be greatly appreciated.

Thank you.

Tony