Apple does suggest that if you don't use your iPad regularly, you should make sure to charge it fully and then drain it completely at least once a month for maximum battery health. And even if you use your iPad regularly, that same complete charging cycle will ensure "proper reporting of the battery's state of charge." Calibrating the battery once a month is essentially feeding the software accurate data about battery life to influence its calculations.
That means you can safely plug in your iPad at bedtime; even if the battery meter hits 100 percent at midnight, it's no problem for your tablet to keep on charging until the rooster crows. The new iPad boasts the same 10-hour battery life that the previous two iPads claimed, though it needs a bigger battery to pull that off--specifically, a 42.5 watt-hour battery, compared to the iPad 2's 25 watt-hour model. That larger battery unsurprisingly takes longer to charge completely than the iPad 2's.
Macworld Lab is currently running some battery tests on the new iPad, and we'll post a story when they're completed.
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