I have a Samsung Google Nexus S I9020A which showed fully charged @ 92%. 100% charging doesn't seem possible. What is the reason?
A Google engineer said (on Google+, I think) that Nexus phones are designed to not charge the battery to 100 %, as it is stressful for the battery. Even when a phone shows 100% and charged, the circuitry actually charges and discharges the battery, always keeping it under 100% (and above 92%, I think).
I tried to find the source, but Google search hasn't turned anything up yet. Will add it here if I find it later.
So when your device does not show 100%, do not panic. That's by design.