As pointed out by Ars Technica, a report on the iPad by Dr. Raymond M. Soneira of DisplayMate suggests the tablet device is not fully charged even when the on-screen meter says 100 percent. Dr. Soneira told Ars that he "measured the power actually drawn by the AC Adapter and found that the new iPad continues to charge for up to 1 hour after it claims to reach 100 percent." He added that "other tablets and smartphones also lie about their charging status," too.
For folks who want to get the maximum juice out of their battery, Dr. Soneira suggests letting your iPad sit in its charging station for longer than the screen recommends. The new iPad takes over five hours to charge from a zero percent state, so you may want to plan your charging sessions appropriately.