A report from Nikkei business Publication show us that battery on iPhone G3 is not replacable. It was a Li-polymer secondary battery, like the one equipped in “iPhone 2G”. The battery supply voltage of +3.7V, but the volume of the battery, etc were not printed on it.
The main board was removed from the lower part of the chassis. A Li-polymer secondary battery, which covers a large area of the chassis, appeared. It seemed to be made in China. Looking carefully at the battery, we found that it was connected to the main board by using a dedicated terminal, like the batteries in Japanese mobile phones. In the iPhone 2G, its main board and Li-polymer secondary battery were soldered.