This expensive accessory is badly constructed in that the micro-USB charging connector is so tight that unplugging the 3-foot long charging cable can destroy the socket. This has happened to me twice. The Apple store, to its credit, replaced the device free both times, but to avoid this happening again I have to keep the cable permanently plugged in to the device - to the detriment of its portability.
A related design weakness is the need to carry a SECOND cable - a standard 3-foot Apple cable - to actually charge ones iPhone/Iphone.
At the very best you will get a 25 percent charge for a third generation iPad. There are much better batteries available at this very high price.
This is not a worthwhile purchase and Apple should not be selling this inferior product