How do I replace the battery in the iPhone 4 and iPhone 4S?

Like all previous iPhone models, the battery in the iPhone 4 models -- the iPhone 4 (GSM) and iPhone 4 (CDMA) -- as well as the iPhone 4S models -- the iPhone 4S and iPhone 4S (China Unicom) -- are not intended to be replaced by an end-user.

When the battery reaches the end of its useful life, Apple intends for one to return the entire mobile to the company to have the battery replaced for a cost of US$79 plus US$6.95 shipping (and applicable sales tax). Apple reports that this service takes three to five business days.

However, more affordable -- and often substantially quicker -- third-party services also are available.

For those with modest technical skills, patience, and a steady hand, battery self-replacement is possible, although professional installation is strongly recommended.

Identification Help

If you are not certain which iPhone model you have, each iPhone can be externally identified by a unique Model Number listed on the back of the phone toward the bottom.

The iPhone 4 (GSM) -- originally intended for use on AT&T in the US -- and the subsequently released iPhone 4 (CDMA) -- originally intended for use on Verizon or Sprint in the US -- are model numbers A1332 and A1349, respectively. The standard iPhone 4S is model number A1387 whereas the iPhone 4S (China Unicom) is A1431.

The iPhone 4 and iPhone 4S models also can be differentiated by the Serial Number with EveryiPhone.com's Ultimate iLookup. The serial number is not externally listed, but it is available when plugged into a computer on the "Summary" tab in iTunes, within the iOS (Settings > General > About), and in the Micro SIM card tray.

In addition to its serial number, EveryiPhone.com's Ultimate iLookup feature can identify iPhone models by EMC Number and Order Number (referred to as "Model" from within the iOS), as well.

Different Batteries

Although the process to replace the battery in the iPhone 4 and the iPhone 4S is quite similar (but not identical), the batteries themselves are different.

Consequently, if you have decided to replace the battery yourself, be sure to purchase a battery for your specific iPhone. In addition, make certain that you purchase your battery from a company with a reputation for selling quality parts. A low quality battery may not hold a charge for as long as a quality one, but it also may leak or even cause a fire.

Battery Replacement Procedure

The battery in the iPhone 4 and iPhone 4S models is attached with adhesive like earlier iPhone models. However, unlike the original iPhone the battery is not soldered and unlike the iPhone 3G and iPhone 3GS it does not involve delicately disconnecting the display (or removing the logic board, thankfully).

It is a bit of a nightmare to replace the iPhone 4 and iPhone 4S displays, but replacing the battery in the iPhone 4 and iPhone 4S is much simpler than earlier models.

Based on hands-on experience and the video below, the procedure effectively is:

1. Turn off the iPhone and confirm it is off.
2. Unscrew two screws on the bottom of the iPhone. These screws could be either Phillips or Five-Point Torx (Pentalobe).
3. Slide the glass back up carefully. Do not remove the back until you hear the "clips" disengage.
4. Be careful to make a note of the grounding clip under the screw or screws that attach the battery to the board and how it is connected to the board for reinstallation before disconnecting the battery. Orientation needs to be exactly the same as originally installed.
5. Unscrew the single Phillips screw that connects the battery to the board for the iPhone 4 or the two Phillips screws that connect the iPhone 4S battery to the board.
6. Disconnect the battery using a nylon pry tool.
7. Gingerly remove the glued battery by carefully pulling the plastic tab or gently using a nylon pry tool on the battery. Depending on the amount of adhesive, this may be slow. Be patient. Do not use a screwdriver or other metal tool.
8. Reassemble the iPhone.

Watch the video below for a demonstration and refer to the potential problems, too.

Battery Replacement Video Instructions

This video from iCracked shows the battery replacement process for both of the iPhone 4 models as well as the iPhone 4S in the hands of a skilled technician:

Potential Battery Replacement Problems

Based on hands-on experience, reports from readers, and Internet comments, these are the difficulties that are most likely to be encountered:

1. Stripped screws. Make sure that you have a screwdriver that is the correct size and head type to use with your iPhone 4 or iPhone 4S. In particular, the bottom screws are tiny and easy to strip.
2. Broken clips. Slide the back glass cover up until you either hear or feel the clips disengage. The distance that the cover moves is tiny, but there should not be resistance when you try to remove the cover. If there is resistance, try to slide the cover up further. These clips are plastic and trying to remove the cover before the clips have disengaged can break a clip. If a clip breaks, you likely would need to purchase a new back for reinstallation.
3. Battery socket issues. Be careful to only pry on the battery connector and not the battery connector socket on the board. There will be some resistance when disconnecting the battery, but not a great deal. Be delicate.
4. Grounding clip issues. On the iPhone 4 (GSM) and iPhone 4S models make sure that the metal portion of the clip is oriented correctly (so that the metal portion will touch the back cover when the cover is back in place). This is the most difficult part of the repair. Pay careful attention.
5. Screw issues. On the iPhone 4S models, the bottom screw connecting the battery to the board is longer than the top one. Make sure you use the correct screws for reinstallation.
6. Plastic tab issues. Do not remove the plastic tab that goes under the original battery when installing the new battery.
7. Electrical shorts. Do not use a metal tool (like a screwdriver) to pry on the battery. Only use a plastic or nylon tool or it can cause electrical problems. Even with a plastic or nylon tool, be very careful to not puncture the battery. Puncturing the battery could cause a fire or injury.

From reviewing the step-by-step instructions, watching the video, and reading the potential problems, you should be able to determine whether or not you feel comfortable replacing the battery yourself or if you would instead prefer to hire a professional. Hiring a professional not only prevents potential problems, but saves a great deal of time as well.

Be sure to purchase your repair service or parts from a trusted company with extensive experience repairing iPhone devices.

Also see:

• How do I replace the battery in the original iPhone (2G)?
• How do I replace the battery in the iPhone 3G and 3GS?
• How do I replace the battery in the iPhone 5?