How to replace the battery in an iPhone 5 (plus 5C or 5S)
Step 1. Turn off your phone by holding down the power button, then sliding the on-screen button to the right.
Step 2. Use your Pentalobe screwdriver to remove the two screws on the bottom edge of your iPhone. Keep all screws somewhere safe, as they're extremely easy to lose if left loose on your work area.
Step 3. Using the suction cup, apply strong (but not sudden) force just above the home button, or to either side of it. You need to open up a small gap so you can begin to pry the screen open. NOTE: if you have an iPhone 5S be extremely careful at this stage. The TouchID cable connects to the bottom half of the phone and is easily damaged if you pull the screen up too far.
Step 4. Using the pry tool, work your way from the bottom more info to the middle of each side to release the clips holding the screen to the phone.
Step 5: You can replace the battery without disconnecting the screen from the phone, but you'll have to hold it carefully at 90 degrees throughout. If you do want to remove the screen, use your Philips 00 screwdriver to remove the metal plate securing the screen's cables to the phone. Then, carefully pry up each connector and remove the screen.
Step 6: Remove the two screws from the metal plate which secures the battery contacts to the motherboard. Each model differs slightly, but they are in the same positions as shown on our iPhone 5 here. The plate remained stuck to the battery connector when we swapped our battery, but it's easy to pry off.
Step 7: Try pulling on the plastic battery release tab to unstick the battery from the case. Usually this will not work as the glue is too sticky. Again, constant pressure is the key, and you should hear the battery slowly unsticking. Our preferred method is to use the pry tool very carefully against the motherboard to ease it up, but there is a risk you could damage a component on the board, so don't apply too much pressure.