20 - 30 minutos
My iPhone was shutting down randomly, even though the battery was charged. The problem appeared most of the time when I was using the phone (making calls, Internet, SMS, ...). The battery was 2 years old.
I ordered the battery replacement kit from ifixit and I received very quickly (I live in Europe and the kit arrived in 10 days!). The repair went very well without any particular problem. Since then, I haven't had any unexpected shutdown and the problem is completely fixed! Thanks!
Be careful when you open the device with the suction cup as you can broke the cables of the display.
Don't buy cheap battery from chinese dealer (most of the time they don't work).