iPhone 4 Battery Replacement

To start the repair, ensure the iPhone's battery is depleted to less than 25% capacity; a fully charged lithium-ion battery poses a fire or explosion risk if damaged.
To prevent electrical hazards and potential damage, ensure the iPhone is completely de-energized prior to starting the repair process.
Determine if your iPhone 4's back cover secures with two #000 Phillips screws or Apple's 5-Point 'Pentalobe' screws, referencing the second image for identification. Use the corresponding screwdriver to successfully remove the screws.
Using either a Pentalobe or Phillips #000 screwdriver, detach the two screws measuring 3.6 mm located adjacent to the dock connector.
To prevent damage, ensure the Pentalobe driver is fully engaged before turning when removing the screws.

Applying gentle pressure, slide the rear panel upwards against the iPhone's upper border.
Expect the panel to shift approximately 2 millimeters.

To detach the rear panel, either gently raise it by applying upward pressure with your fingers or secure a Small Suction Cup to the panel and lift.
Exercise caution to prevent harm to the plastic clips affixed to the rear panel.
Before attaching a replacement rear panel, peel away the adhesive backing from the protective plastic covering the camera lens’s interior surface, and also remove the sticker adhered to the large black area located adjacent to the lens.

Using a Phillips screwdriver, detach the battery connector from the logic board by unscrewing the single 2.5 mm screw that holds it in place.
Certain models incorporate a second screw; this secures the contact pad situated directly above the screw highlighted in red within the accompanying image.

Carefully lift the battery connector away from its connection on the logic board, utilizing a plastic opening tool to avoid damage.
To avoid connector damage, release the bracket by gently separating it from above and below, as side access is limited.
Exercise extreme caution when releasing the battery connector, ensuring you apply force only to the connector itself, as applying pressure to the logic board socket risks irreparable damage.
Carefully detach the metal clip, which secures the antenna connector.

1. Carefully extract the battery from the iPhone by utilizing the provided transparent plastic tab for a gentle upward motion.
   Should the battery retaining tab fracture prior to separation, introduce a small quantity of isopropyl alcohol with a concentration exceeding 90% beneath the battery's edge. Allow approximately one minute for the alcohol to dissolve the adhesive bond. Then, gently insert a spudger beneath the battery tab to detach the adhesive.
   To avoid damage, do not attempt to force the battery free; instead, if the adhesive remains strong, add additional drops of alcohol to soften it. Ensure the pry tool does not puncture or bend the battery during removal.
2. To prevent damage, ensure any residual alcohol solution is completely removed by wiping or by letting it evaporate fully prior to battery installation.
   Carefully detach the protective plastic packaging from the new battery by gently separating it from the ribbon cable.
3. Ensure the red contact clip is correctly situated adjacent to the battery connector prior to reattaching the battery connector.
4. To prevent wireless interference, use a de-greaser like Windex to thoroughly clean all metal surfaces that will be in contact during reassembly, as oils from handling can create problems.
5. Following reassembly, execute a complete system reset to mitigate potential problems and streamline any subsequent diagnostic procedures.