Early yesterday Macrumors reported that the iPad 3 battery continues charging -- even after the menu bar icon reports that it's "100%" full.
Ray Soneira, President of DisplayMate Technologies Corporation, took a deeper dive and discovered that the iPad 3 battery isn't fully charged until 2 hours and 10 minutes after it says so.
The charge indicator on all mobile devices is based on a mathematical model of the charge rates, discharge rates, and recent discharge history of the battery. It uses this information to estimate how much running time is left. It's actually rather difficult to do because most batteries degrade slowly as they discharge and then tend to surprise with a precipitous decline near the end.
So there is something wrong with the battery charge mathematical model on the iPad. It should not say 100% until it stops recharging and goes from the full recharging rate of about 10 watts to a trickle charging rate of about 1 watt. Otherwise the user will not get the maximum running time that the iPad is capable of delivering, which is listed in my iPad shootout article.
Soneira's final results:
At 2:00 hours after reporting 100% charge the new iPad hardware started to reduce the charging power. At 2:10 the recharging cycle fully terminated with a sharp decrease in power.
The new iPad battery is truly fully recharged 2 hours and 10 minutes after prematurely reporting on screen that it was fully charged.
I'm guessing that Apple will fix this in iOS 5.1.1?