5 - 30 minutos
My 20 month old iPhone 4 lost about half the charge capacity. Rather than upgrading, I decided to try a replacement battery.
The disassembly and battery replacement was fast and relatively smooth. Only had to be careful about the battery removal. There was a lot of adhesive underneath the original battery which took some time to convince to let go. Otherwise smooth sailing.
Well worth the time and effort. My battery capacity is back to that of a new phone.