iPod Touch 3g Battery
Is the battery plugged in or soldered?
It is soldered to the board, as seen in the picture on step 12. Also, the battery uses a thin ribbon cable whose solder points are essentially holes through the ribbon cable itself, so it is difficult to solder but definitely possible (I've done it before).
I just joined this forum and did this myself on my 2nd gen iPod touch and it is my believe that one of the three battery connection or solder points, specifically the middle one, does not have a solder plate or line underneath it like the other two, which were very easy to solder back on, but the middle one gave me the impression I overheated and removed it, but there are no traces of a plate in the middle, not even at the old battery's middle connection point.
The three points all have metal connection which need solder!! if you over heat the board its hard but if you roll the solder directly below to the gold point you will return the connection!! you can also slip the lifted pad back in place and solder the two outside points down then solder the middle one last and this will actually hold it down and keep connection as well.