The battery was no longer holding a consistent charge. The meter showed near full, but phone would power off.
The phone would drop calls. Not good. iPhone 4S $400+, not good.
iPhone 3GS battery replacement. Successful.
Go slow. Have a pill case to hold your screws while working on the phone. The video was a great help but next time please zoom in tight when showing how to work with those ribbon cables. Thought I broke the ribbon the first time I detached from the main board.
All is well, my old 3GS buddy is hanging in there and is good as new! Thanks for a great product at a great price.