Ok if you would have checked forum before posting this thread I just put a thread up about this same issue... This is my second morning now of removing the phone off the charger from charging it overnight and it saying fully charged 100% and then within like 5 mins or so it drops to like 89% without me barely doing anything and then I look at battery usage and it shows Android system at 57%. I don't know what to do, I have done the task killer and stuff, for the most part the rest of the day its fine, but why is it dropping so fast to start with? I'm wondering if its because once the battery is fully charged its stops charging, but i don't know any help would be appreciated!
Someone responded in other thread saying It's a software thing. When the battery is fully charged, the system is only interpreting it at 90%. As long as it doesn't drop to 80% in 5 more minutes, it's normal for the time being.
I don't know if thats right as it seems weird but maybe and I am glad to see its not only me seeing this. And people I know how to turn things off and I have them off that is not the problem.