We placed the iPad 2 and the new iPad next to each other after removing their LCD panels and compared them. There was a clear difference between them. While there was a long and narrow space to the left of the iPad 2's main board, this space was narrower in the new iPad. And the rechargeable battery of the new iPad was wider than that of the iPad 2.
"Its inside is almost filled with the battery," a squad member said.
There was another clear difference. In the iPad 2, there was a coaxial cable running from side to side as if it traversed the battery. And it connected the main board and a sub PCB (printed-circuit board). On the sub PCB, there were a rear camera module, acceleration sensor, angular velocity sensor, etc (See related article).
On the other hand, the rear camera of the new iPad was connected by using a flexible cable located in the upper area, like other parts including the front camera. Therefore, the coaxial cable running between batteries was eliminated. This is clearly a more rational design.
The capacity of the iPad 2's rechargeable battery is 25Wh. Because its voltage is 3.8V, the capacity is about 6,580mAh in terms of current. On the other hand, the new iPad's battery is printed with characters "3.7V, 43.0Whr, 11560mAh," meaning that battery capacity increased by about 76%. Because the iPad 2 and the new iPad have almost the same battery life, the power consumption of the new iPad is probably much higher.
To compare the batteries of the iPads, we took them out from the cases. In the iPad 2 and the new iPad, their batteries were firmly attached to the bottom halves of their cases with very adhesive tapes.
It is dangerous to heat a lithium-ion rechargeable battery with a heat gun. Therefore, we used only the spatula. We tried to carefully peel off the tapes so that the batteries were not damaged. Still, we often had to rely on sheer force.
After placing the batteries next to each other, we found that the battery of the new iPad was clearly longer than that of the iPad 2. Also, the new iPad's battery had a larger area and thickness.
Then, we moved on to compare their main boards. Though their sizes were almost the same, their shapes were slightly different. And, after taking them out, we found a larger difference.