5 - 30 minuten
My iPhone 4 was not charging like it should. While plugged into the wall charger the battery level wouldn't go past 30%. After trying several different chargers, it eventually began charging normally and it charged back up to 100%. About a week later the problem returned and it eventually died. I decided to replace the battery because it's an easy fix since I'd already replaced the original battery.
This time wasn't as easy as the first time. The battery I was replacing had gotten hot enough that it actually melted the connection to the phone. I had to pry off that portion of the power strip. Then I realized my iPhone model requires a #000 Phillips bit to remove the screw that holds the antenna in place. Apparently I had used the #00 Phillips to remove it the last time I replaced the battery, but this time when I tried I just stripped out the Phillips slot on the screw head. So I decided to use a Dremel tool to cut a slot in the #000 screw and use a small flat head to remove it. My thinking was worst case scenario, I would destroy the phone and replace it with an iPhone 5. But the Dremel tool worked and I was able to replace the battery once more.
Make sure you have all the correct size screwdriver bits before you start your repair.