Fuzzy Math: The New iPad’s Battery Keeps Drawing Power Past 100%

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The new iPad’s been in the media crosshairs all week for alleged battery-related problems. First, we heard the system was notably toastier than its predecessor — a problem naturally exacerbated by using it while the battery charged. Then we heard from Consumer Reports that the new iPad’s battery drains while playing certain games, despite being plugged in (my colleague Jared Newman, along with several others, have been unable to replicate this “issue”). And now Dr. Raymond Soneira, president of DisplayMate Technologies, is claiming in a detailed review of the new iPad that Apple’s tablet isn’t being entirely honest with us when its battery charge display shows “100%.”

“Note that the batteries do not actually reach full charge when 100% is shown and need up to an extra hour before the charging actually stops,” writes Soneira in his review. Note that the new iPad’s battery is considerably larger than the older iPad 2’s: 42.5-watt versus 25-watt.

(MORE: Consumer Reports‘ iPad Battery Claims Don’t Check Out with Us)

According to iLounge, which exchanged emails with Soneira, the iPad “continued to draw 10W” of power for “up to an hour” after iOS indicated the battery was full. That partly jibes with iLounge’s own experience with the device:

In iLounge’s testing, the new iPad switches from a lightning bolt (“still charging”) to plug (“done charging”) battery icon 5 to 10 minutes after reaching 100%; Soneira confirmed that the iPad still charges even when it claims to have been filled.

That’s not all: iLounge says it found “unusual, non-linear reported battery drain during our numerous battery tests, with the third-generation iPad sometimes reporting a battery loss of just two percent over the first hour of testing, then averaging 10% of loss each hour afterwards while performing the same tasks.” So either the battery itself is flawed, iOS is interfacing improperly (or inconsistently) with the battery cell and misreporting, or there’s something arbitrary going on in the background during these tests that hasn’t yet been accounted for.

Okay, there’s a fourth possibility, though it sounds a trifle conspiratorial: iLounge wonders whether Apple may have “taken certain liberties when reporting battery levels to give the impression of faster charging and slower loss.”

While there’s nothing you can do about the alleged battery charge readout issues, Soneira offers some helpful advice on squeezing more time overall out of a charge. Running the backlight at maximum brightness, DisplayMate’s tests clocked just under six hours of use. But if you drop the slider to “Middle” brightness, Soneira found the run time leapt to 11.6 hours, “almost identical to the iPad 2.”

MORE: The New iPad Is Out. What Now, Everybody Else?