We lift up the LCD to reveal the battery.

The battery is labeled with the same model number (A1389) as in the last round, so it's no surprise that it's another 3.7 V, 43 Whr package.

Like the iPad 3, the battery is adhered very securely to the rear case. Since batteries are consumables that wear out, the trend of glued-in, hard-to-access batteries in iPads and other Apple devices is unfortunate.