iFixit

We get a good look at the battery, and find ourselves scratching our heads a bit.

This is a 3.72 V, 16.5 Whr, 4440 mAh battery.

Or maybe it's a 3.78 V, 16.9 Whr, 4400 mAh battery?

Or maybe it's a 3.72 V, 4400 mAh battery?

Or maybe, according to Apple's tech specs, it's only 16.3 Whr.

Whatever the capacity, it's decidedly mini when compared to the massive 43 Whr battery in the iPad 3. Even the venerable iPad 2 sports a 25 Whr package, 50% more than the iPad Mini.