My iPhone 3GS of 2 1/2 years decided to start shutting off whenever I would try to use an app, search the web or anything that seemed to need any processing power. I had no problems as long as it was plugged in to a charging jack. I tried resetting, restoring and reinstalling the OS and iTunes. No luck and a big waste of time. I went to my service provider to see if they had any advise, they just wanted to sell me a new phone. Told me that these phones only work for 2 years or so and I was lucky it had been ok so far. After looking at a friends 4S and not being impressed by the new features other than the display I decided to wait for the iPhone 5 (or whatever their going to call it) or see if I could get it fixed. I started searching for repair options. After a few hours of searching the web and looking at videos I decided to give it a shot myself. Twenty bucks didn't seem to be too much of risk and I figured it had to be the battery. I placed my order with iFixit at 11 p.m on 3/28 and received it on 3/31. The new battery (with a pry tool and small screw driver), the Spudger and the suction cup came well packaged and in perfect condition. Total cost $30.85.
I could not believe how easy Apple has made these things to replace parts. Other than the "Do Not Remove" sticker hiding one of the main board screws a first timer with no instructions and a little knowledge of zif (zero insertion force) connectors could do this easily. Total time was about 30 minutes including a little clean up from 2 1/2 years of pocket lint around the dock connector and front panel seal. The battery is identical to the original and fit perfectly!
iFixit: Put a smaller screw driver in with the battery!
The one that came with the battery did not fit the screws on my phone and could easily have stripped them. I had another set so it was not a problem for my repair.
User: Order the Spudger (makes life easy) and the Suction cup if you dont have one! DO NOT BREAK YOUR DISPLAY TRYING TO PRY IT OUT AS SEEN ON OTHER VIDEOS AROUND THE NET! Prepare a flat work surface and lay out a light colored dish cloth to work on. The screws are very small and the light color makes it easy to see them and lay out in a pattern the way they are removed. Also have a wet nap handy for clean-up. I used a coffee filter and a little denatured alcohol. Take your time removing the battery! Pry on it gently from several areas a little at a time. I broke the little pry tool trying to get mine out. It was really stuck! When your ready to replace the front cover, gentle staighten out the #3 ribbon cable by running it between your fingers and just let it gently find its way in (the lock must be in the up position!) to its slot. ZIF connectors should require "Zero Force" I actually will be removing the front display from now on to replace screen protectors. It makes easy work of getting them on perfectly.
I am happy to say this repair fixed my problem and it was easy and inexpensive. My iPhone 3GS is working perfectly again and I am sure it will last until the new iPhone is released. You have restored my faith in Apple and my investment in such an expensive device.
Thank you iFixit!!!