20 - 30 Minuten
My original iPhone 3gs battery went out and I had it replaced at a local repair shop. After the battery was replaced I tried to restore my phone in iTunes. This was unsuccessful and I kept getting the message 'error code 29'. After reading several forums it was evident the battery was the issue.
Ordered the recommended iPhone 3gs battery from ifixit and followed their instructions on how to install. This solved my issue. I was able to restore the phone with no error codes.
The only tricky part of the install was getting the logic board back to its original position so that the sim card would slide back into place and ribbon #7 was not the easiest to reattach.