Battery would show 100% and as soon as I would go on the Internet it would drop to 2% and the phone would turn off. My battery was clearly done.
Very easy instruction manual. Had some issues putting it back together as I kept having trouble with getting the SIM card holder to align... until I figured out that the connectors would keep getting underneath the battery. Once that was resolved the whole process was a breeze. Would do it in a few minutes now and my phone is better than new!!! Can't remember my battery lasting for so long before.
Make sure to put your screws in a safe place. I managed to loose one by shuffling paper on the table... they're so tiny. Also remember that connectors 1 to 3 stay with the cover of the phone. I forgot and had to redo the whole process twice because I thought they were hidden under the battery... my mistake.