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DisplayMate: Your New iPad Might Not Be Fully Charged at 100%

Typically, a 100% figure on your battery indicator means it's time to pull the plug. But this may not be true for your new iPad, according to new research by Dr. Raymond Soneira of DisplayMate Technologies.

According to Dr. Soneira, all mobile devices use a certain mathematical model for their charge indicators, which is based on charge rates, discharge rates and recent discharge history of the battery. Using these numbers, it calculates and estimates how much running time your gadget has left -- which is actually pretty difficult to do since most batteries degrade slowly as they discharge, then will typically surprise the user with a quick drop-off toward the end.

Dr. Soneira says that on the new iPad, this mathematical model isn't quite working correctly. "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," he wrote to us in an email. "Otherwise the user will not get the maximum running time that the iPad is capable of delivering."

 Soneira says that he measured the power drawn by the AC Adapter and found that the new iPad continues to charge for up to one hour after it reads 100%. He claims that it's not only your iPad that does this -- other tablets and smartphones also lie about their charging status. So if you're particularly scrupulous about fully charging your gadgets, you may want to leave them suckling on a source of juice for at least an hour after your indicator says 100%.

While we haven't verified these results ourselves, Soneira's article on the topic is pretty thorough. You can head over to Displaymate to read his full analysis yourself.