My iPhone was dying when it was cold outside, and it would just randomly die when it said it was around 50%.
I had to take the phone apart three times. First, to replace the battery as instructed. Secondly, to connect wires which I hadn't properly reconnected. Third, my home button was not working properly, so I had to modify a copper wire to make it work. It definitely took some work and some innovation, but I figured it out (with your help!) and my phone doesn't die when I walk outside now! Also, I learned a lot about my phone as a result of the repair process. Thank you!
Read the instructions all the way through before proceeding with the repair! I tore one of the adhesive strips and tried prying the battery up far enough to reach the remainder of the strips, which bent the old battery and was probably not safe. I didn't realize that there was a safer way to proceed once that happened although the instructions were right in front of me. However, that could have been avoided if I had read ahead first.
Also, when the instructions say pull the adhesive tabs slowly, they mean SLOWLY. Go slow and save yourself some trouble.