20 - 30 minutos
The Iphone had a strange behaviour, it suddenly shuts down with black screen, even at 90% of battery charge... After that I had to plug it to the charger...
Perfectly, the guide is reliable.
I first bought a battery from ebay, at ridiculous price, near 3/4 euros. Well, it was a very bad idea, it even couldn't full charge and then it broke. So I wanted a replace more solid, and found Ifixit. Problem solved!