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More LEDs in new iPad can mean less battery life

More LEDs in the new iPad means Apple has maintained a high level of brightness but not battery life necessarily.

Brooke Crothers Former CNET contributor
Brooke Crothers writes about mobile computer systems, including laptops, tablets, smartphones: how they define the computing experience and the hardware that makes them tick. He has served as an editor at large at CNET News and a contributing reporter to The New York Times' Bits and Technology sections. His interest in things small began when living in Tokyo in a very small apartment for a very long time.
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Brooke Crothers
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The new iPad's Retina display (R) compared to the iPad 2.
The new iPad's Retina display (R) compared to the iPad 2. Apple

By doubling the number of LEDs in the new iPad, Apple cut somewhat into battery life--particularly when used at full brightness--something you won't find on Apple's tech spec page.

Though the new iPad's battery is 1.7 times larger than the iPad 2's, all of those extra LEDs still take a toll on battery life at full brightness--as Raymond Soneira, president of DisplayMate Technologies, told CNET in a phone interview yesterday.

"The [power consumption of the] LEDs is 2.5X compared to the iPad 2, and the battery is 1.7X [larger]...so what happens is that if you run your new iPad at full brightness, the battery run time is less because you only put in 70 percent more battery but you're using 150 percent more power," Soneira said. (See chart below.)

The new iPad at maximum brightness has about 20 percent less battery life than that of the iPad 2. At middle brightness battery life is pretty much the same. Note that in DisplayMate Technologies' testing the iPad is in Airplane Mode with no running applications
The new iPad at maximum brightness has about 20 percent less battery life than that of the iPad 2. At middle brightness battery life is pretty much the same. Note that in DisplayMate Technologies' testing the iPad is in airplane mode with no running applications. DisplayMate Technologies

While full brightness battery life went south, lower settings are pretty much the same. "So, at full brightness the new iPad lasts 20 percent less than the iPad 2. But in the middle range, the new iPad runs essentially at the same running time as the iPad 2. And, in fact, that's the way Apple delivers it and that's probably the typical setting," he said.

More specifically, that's the brightness slider set at 36 percent, Soneira said today in a follow-up interview. He described this as more or less as the default setting on the iPad.

Still, there are plenty of people--just check out the Apple Support Community forums--who insist on using the iPad at full brightness.

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It all comes down to LEDs. The number of backlight LEDs has roughly doubled from 36 to an estimated 72 to 82, according to Soneira. "Since the display normally consumes about 50 to 60 percent of the total tablet power, the new iPad needs at least a 50 percent larger battery," he said in report, echoing what he told CNET above.

Soniera's analysis meshes more less with a test CNET's Eric Franklin conducted on the iPad over the weekend. He evaluated the battery life by continually running a movie file on the iPad until its battery dies. The new iPad drained in 12.8 hours, faster than the iPad 2's drainage rate of 14.2 hours. But Franklin points out that 12.8 hours of battery life "is still the second-highest result we've seen on a tablet using a single battery."