10 - 30 minuten
Live in Chicago, left my phone in the car overnight in sub-zero temperatures. Ever since then, battery life has been about 2 hours.
The instructions were good except for a couple minor points that were a little unclear, and a HUGE point which wasn't mentioned and made the repair a little challenging. The unclear points came at the step of removing the little piece that actually connects to the battery. The pictures are so zoomed in, that it's a little hard to tell where you are in the phone. It would be nice to have the bird's eye view first, then a little circle that points to a blown-up section. It also wasn't mentioned that there is a super tiny piece, which is a little black right angled thingy with a little copper piece that apparently makes contact with the rear panel of the case. Maybe it's a ground? my description would be "super tiny telegraph key." Anyways, that piece isn't connected to anything, except the screws you have to remove to take the battery retainer off. So the tiny telegraph key immediately falls off, and is 2 mm wide and seems important not to lose. But more important is that no one mentioned that every darn thing in the phone is MAGNETIZED and the super tiny ridiculous screws are MAGNETIC. Whose genius idea was that, I wonder. So in the next-to-last step when you are all finished replacing the battery and you have managed to put tiny telegraph key back in place for the 16th time, and are ready to screw in the super tiny screws, every time you get within an inch of the phone, the screws jump off the end of the screwdriver and stick to the hard drive. This was the single most challenging part of replacing the battery, and wasn't even mentioned in the guide. Of course, half the times the screws fell down into the circuit boards and I had turn the phone over and shake then out, which was difficult since they were held in place by the magnets. Took maybe 10 tries to finally shove the screws in the holes with my fat fingers since I don't have a pair of 6 mm long miniature tweezers. On one try, though, a screw fell out onto the floor, and I had to sweep my office with a strong magnet for about 15 minutes before I found it.
One simple piece of advice to Apple: use non-magnetic screws. for the sake of all of us.
To the ifixit staff: thanks for your helpful guide and for existing to allow techy-people like myself the ability to void our warranties and do what we want with our own belongings.