March 30, 2012, 9:17 AM — You can't talk battery life without running battery tests. So that's what Macworld Lab has been busy doing the past few days. Our results: The third-generation iPad lives up to Apple's promise of a 10-hour battery life in some cases. But the iPad 2 outperformed the new tablet in our testing.
That's a bit of surprise. When it unveiled the new iPad earlier this month, Apple said that battery life of the new model and its predecessor would be similar.
To test the iPad's battery life, we took a fully charged iPad, connected it to our local Wi-Fi network and played back a movie in full screen mode until the battery died. We did this with two different brightness settings—full brightness and at a measured brightness of 150 cd/m^2. (That's candela per square meter—a measurement of luminance.)
Battery tests take a long time and having to manually restart a movie each time it finishes can be a hassle. Luckily, 1963's Cleopatra has a running time of over 4 hours and is available on iTunes, so I don't have to watch over the iPad constantly while testing. (I will, however, take this opportunity to publicly request that Apple include a looping feature in the next version of iOS similar to that found in the company's QuickTime player for OS X. Can't hurt to ask, right?)
There's been some debate lately over when a fully charged iPad is really a fully charged iPad. We'll leave that issue for the folks at DisplayMate to grapple with. Our tests with a power meter showed the new iPad to start dropping its power draw when its battery life indicator got to 90%. It started dropping a little quicker between 95% and 100%, at which time our meter showed the iPad drawing 4 Watts and continuing to drop. Thirty-five minutes after hitting 100%, the iPad stopped drawing power.
To be on the safe side, we ran our battery tests after the iPad's indicator stood at 100% for at least an hour.
An iPad 2 with its screen at the brightest setting and with automatic brightness turned off and that's also connected to a Wi-Fi network can play a movie at full screen for around 8 hours 30 minutes. The new iPad, using the same settings, stops after about 5 hours 40 minutes. That's a pretty big difference for devices that are supposed to perform similarly.
One thing causing that difference in battery life is the difference in each device's maximum screen brightness. Using a light meter, we found the max brightness on the iPad 2 to be 400 cd/m^2, compared to the new iPad's 434 cd/m^2 measurement. The new iPad having four times more pixels than the iPad 2 would come into play here, too, of course.