iPhone 4 not charging to 100%

[OrangeCuse44]

I originally thought this was a battery calibration issue when I first got my iP4, so I drained the battery completely and charged for 8 hours. My nightly charge routine is sync, turn off while still docked to Mac, then either close the lid to the Macbook or leave it open. Sometimes I'll wake up to 100% charged, other times it could be 80%. Is the iP4 not designed to charge when turned off and docked to a computer or is there another issue?

 

[celticpride678]

The last 20% of the charge takes the longest. Could that be it?

 

[OrangeCuse44]

The last 20% of the charge takes the longest. Could that be it?

Don't think so. Its plugged in for 7-8 hours. I used 80% as a general number. Last night for example, I plugged it in at 40% and awoke to it only being at 68%.