New battery goes flat FZ1n

[sidewaysid]

I put a new battery on my bike FZ1 every year, and if I don't keep it on the optimiser, it flattens within a week, it is now un rideable really for fear of getting caught out. I think there is a bad earth or a leak to earth, but recently I have seen a lot of stuff with the Alternator/generator falling to bits, does anyone have a clue as to what it might be. Thanks guys