I have had a few issues with starting my 02 600cc Fazer the last few weeks.

The battery is fully charged using an oxford maximizer 360T charger one day, use the bike that day, stored in shed overnight and next day there is not enough power to start the bike.
I have checked the altenator which seems to be returning current to the battery OK.
The battery was new beginning of last year, it should still be ok I think

The only other thing I can think may have something to do with the problem is that I have a Meta m357 alarm installed, could it be draining the battery?
I have been leaving the bike outside the kitchen window(its covered with a stormex cover) the last few weeks so I can charge it over night, but with the amount of bikes being nicked at the moment worries me.
Any help or suggestion on what to do are welcome.
Cheers