Preview at WWDC likely in June, followed by September launch.
Photos of 'iPad Mini' Battery Reveal 16.7 Watt-Hour Capacity
While we can not confirm the authenticity of the part, the markings are consistent with those seen on batteries from other Apple products. The battery's proportions also seem to fit fairly well with what is expected for the iPad mini, although the exact dimensions of the part are unknown.
The 16.7 watt-hour capacity for the iPad mini battery unsurprisingly places the device between the iPhone 5 at 5.45 watt-hours and the third-generation full-size iPad at 42.5 watt-hours. Given that the iPad mini has been said to be based more on the iPad 2 and lack a Retina display, the iPad mini's battery may be more appropriately compared to the 25 watt-hour battery of the iPad 2.
The battery is clearly not yet an official part ready for shipping, as it contains placeholders for several portions of regulatory text and blank rectangular placeholders for a number of regulatory logos. It seems likely, however, that this is the final design simply awaiting final certification.
Apple is expected to introduce the iPad mini at a media event all but confirmed to be scheduled for October 23.