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DisplayMate: New iPad Lies About Charging Status

The new iPad is displaying a 100% charge when it still has two hours to go. But that's par for the course with tablets, DisplayMate Technologies says.

March 23, 2012

Updated 1:00 PM ET with new data from DisplayMate.

The new Apple iPad keeps charging for more than two hours after it says it has a full battery, Dr. Raymond Soneira of DisplayMate Technologies said after testing the new tablet's display. 

"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," Soneira said in an email to PCMag.com.

The iPad isn't alone in this. "Other tablets and smartphones also lie about their charging status," Soneira said in another email.

The problem is an inaccurate battery-charge display algorithm, Soneira says.

"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. ... So there is something wrong with the battery charge mathematical model on the iPad," he said in his e-mail.

Soneira, a leading display analyst, has worked with PCMag.com before in helping to analyze monitors, TVs and portable displays.

As the new 2048-by-1536 display's backlight takes 7 watts of power compared to the iPad 2's 2.7-2.8 watts, according to Soneira's full report, the new iPad requires a much bigger battery.

But the new iPad uses the same power adapter and internal charging circuitry as the old one, with a 10-watt power adapter. That means the bigger battery takes longer to charge.

In our tests, we found that the new iPad took about seven hours to show a 100% charge, while the previous iPad 2 took about four hours. Soneira now says to add two hours to be sure.

According to Soneira's other tests, most other 10-inch tablets - including the Motorola Xoom, Asus Transformer TF101 and Acer Iconia A500 - have about the same screen power draw as the iPad 2. The Samsung Galaxy Tab is between the iPad 2 and new iPad, at 3.3-4.7 watts.

None of those tablets have anything close to the new iPad's 2048-by-1536 resolution, though. The first Android-powered tablets to approach that resolution will probably be the upcoming Asus Infinity TF700 and Acer Iconia A700, with 1900-by-1200 screens. Those tablets are tipped to be coming out sometime later this spring.