Having resoldered the 4 battery connector pins (1 using a jump wire because the soldering pad got off when the connector detached from the board), I got the phone to turn on but the battery wouldn't charge either.
I finally seem to have solved the problem, which for me seem to have been that the 2nd connector was grounded due to the small prong connecting the back case: i inserted a plastic sheet in between to prevent contact and seemed to have done the trick =) also be careful that the metal plate covering the battery side connector doesn't come in contact with any of the newly soldered contacts.