Help Weird battery usage graph. 69% by 'Android OS'

[fudashiii]

Hey,
My Galaxy S2 battery is usually pretty good. But the last two days it has been awful with no change in usage. Take a look at the graph below, the discharge rate starts a pretty normal rate, then suddenly it gets much steeper after about an hour and continues like that all day. Nothing changed in my usage to cause the dramatic increase in discharge rate... any ideas?

Yesterdays graph looked virtually identical too.

Oh and also, 69% of the usage is from 'Android OS'?!

Thanks a lot.

 

[KTP]

its a common issue for the S2, if you check the stats and Android OS is showing high usage, the easiest thing is to reboot the phone.
it should start behaving and be less of a drain.
not sure if any of the updates fixed this or not, i'm using a custom rom and dont seem to suffer from it anymore but it used to annoy me.