If you have had an iDevice for some time, then you may have noticed that when the battery says it is 100% charged, the battery icon still tells us that it is charging. Only when a cable appears instead of the lightning can you disconnect the device from the power supply because theoretically only then the battery is 100% charged. This is how Apple thought of the charging system for iDevices, but it seems that it is not perfect because the devices continues to take power from the charger even after they say they are fully charged.
I 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%. This affects the battery run time if you stop charging when it says 100%. If getting maximum battery runtime out of your device is crucial, people need to keep recharging their new iPad for longer than iOS claims. So if you're charging your new iPad for eight hours every night, time to start charging it to 9 if you really want a full charge for the day ahead.
The statement comes from the president of the Display Mate company who claims that the iPad 3 tablet charges for another hour after the iOS says that the battery is fully charged. He checked the current drawn by the iDevice through the power supply and noticed that although the iOS says that the device has been charged, it still draws current through the power supply as if it were charging. Until now, the president of Display Mate was right in everything he said and if you have the opportunity, leave the iDevices a little longer to charge to have a better autonomy.
This theory is several years old, but at regular periods of time it is brought back into discussion.
