I have a iPhone 4s that had not been fully charging when left on the charger over night. Majority of the time it will be at 100% when I take it off in the morning and depending on its use, and if it has had a full discharge recently, it seems to keep a charge somedays better then others. My issue is maybe once a week, every 10 days, it will not be at 100% when I go to take it off the charger. Last night it was around 60% when I put it on the charger for the night and this morning it was at just 92% in 6 hours of charging. Any one else having this issue? solutions?