sudden iphone battery drain
i just had the weirdest thing happen to me today. i've had my iphone 4 for exactly 2 years now. i left it last night with 80% battery, slept for 8 hours, woke up to find it at 35%. wifi was off, no programs were running except for: calendar, messages, settings, skype. there were no notifications at all.
my normal battery drain during night time is between 5% and 7%. i have never had a 50% drop! but i usually don't leave skype running. the phone is running the latest ios (which i think is 6.1)
this happened to me once only on ios 5, but i had left the phone for 6 hours in a poor reception area. however last night it was at home, which is normally a good reception area.
my question is: could this have been skype running, or is it possible that i had lost signal at some point and the phone was searching all night? and if so, should this drain 50%?
is there a solution or a way of finding out what's wrong?