20 - 30 minutos
My iPhone 3GS is now 3.5 years old. The running time of my battery was very low with a standby time of only a few hours. I had to charge it several times a day, and sometimes, when the charge was below 50%, my iPhone shut down when I used it. So I decided to replace my battery.
I replaced my battery yesterday. It took around 50 minutes to change my iPhone battery, but it was not very difficult. The main difficult task was the correct replacement of the logic board.
After the operation, when I turned on my iPhone, it was blocked after I entered the PIN code and did not managed to unblock the SIM card. I was a bit afraid: did I damaged my SIM card or the SIM card slot during the operation? Finally, I put the SIM card of a friend in my iPhone and it worked. After this test, I put my SIM card in my iPhone and it worked correctly. The problem was maybe due to dust on my SIM card or on the SIM card slot.
My iPhone is now working correctly with its new battery.
The Ifixit guide for the battery replacement is very clear, so I have no technical advice to add.
The only advice I can give is: when you do it, do not drink coffee before, stay calm and take your time during the operation!