20 - 30 minuten
I use my iPhone a lot and its 3 years old. The charge time began to shorten considerably. When it got to 50% charge it would die without the normal 20, 10, 5% warning. Eventually it would die out at 70 - 80% charge indication. I knew that this was a battery issue and feel that it lasted quite well considering the heavy use for 3 years. So its time for a new battery.
The replacement process went well. I am retired from an electronics career and so this was a fairly familiar task for me. However, this shouldn't discourage one with a little dexterity and patience from replacing their battery. I am thorough with my work so in addition to iFixit's video, I watched a number of different versions of the procedure before I opened the case. It did take me a lot longer than the 20 minutes one of the videos mentioned that it took. I think that varies from phone to phone. Depending on how cured the mounting glue on the old battery is and connector #3, it could take longer. For me taking a little more time in order to do it right and have success with it is preferable. My battery was P/N 616-0435. The one that I received with the spudger and screwdriver tools was P/N 616-0434. I understood that any of 3 P/N's 616-0433, 0434, and 0435 would work. The -0434 worked fine. The new battery has brought the phone back to its original performance. Thanks ifixit for the great product and support.
Key thing is to take your time, have patience, and be gentle with the flat cables and their connectors when disconnecting and reconnecting them. Do apply sufficient pressure to the connectors to insure that they are connected well. I didn't get connector #2 completely secured. As a result when I booted the phone up, the left side of my multi-touch screen had intermittent response to my inputs. It was hard getting the "slide to shutdown" to work so that I could open it back up and address the problem. It took several attempts of swiping it really fast. Sure enough when I did get it powered down and opened up, I looked in from a side view and #2 was slightly up on one end. Applying a little pressure secured it, and its worked fine since then. Also, be sure to flip up the little black connector release on #3 connector before pulling out #3 connector. Use the spudger tool to coax the #3 flat cable out toward the top of the phone. When reassembling, flip it back down after reinstalling #3 connector. This is not shown with enough detail in your ifixit video. Hope this helps those that are contemplating doing this.