|Installing iPhone 4 Battery|
Step 1 — Battery
Push the rear panel toward the top edge of the iPhone.
The panel will move about 2 mm.
Remove the rear panel from the iPhone.
Remove the single 2.5 mm Phillips screw securing the battery connector to the logic board.
Use an iPod opening tool to carefully pry the battery connector up from the ends closest to the top and bottom edges of the iPhone.
Do not pry against the pressure contact.
Remove the pressure contact from the iPhone.
Use the clear plastic pull tab to gently lift the battery out of the iPhone.
Be careful when removing the battery with the plastic pull tab. On some units, Apple uses an excessive amount of glue, making it virtually impossible to remove the battery in this fashion (with the tab possibly tearing due to excessive force).
For batteries that "stick", you could use the iPod opening tool to assist (take extra care whilst doing so).
Remove the battery.
Before reconnecting the battery connector, be sure the pressure contact (shown in red) is properly positioned next to the battery connector.
Before reassembly, be sure to clean all metal-to-metal contact points on the pressure contact as well as its contact point on the rear panel with a de-greaser such as windex. The oils on your fingers have the potential to cause wireless interference issues.