Your iPhone battery needs replacement when it no longer holds a charge through a normal day, not when it gets old

Apple designs iPhone batteries to retain 80 percent of their original capacity after 500 full charge cycles. A charge cycle means draining the battery from 100 percent to zero and back to 100 percent — not necessarily in one day. If you charge your phone to 50 percent, use it, then charge it again, that counts as half a cycle.

The real signal to replace your battery is not age but behavior: your phone shuts down unexpectedly at 20 or 30 percent charge, or it cannot make it through your normal day without a charge. If your iPhone still lasts a full day and does not shut down early, the battery is working as designed, even if it is three years old.

You can check your battery's actual health in Settings > Battery > Battery Health & Charging. Look at the "Maximum Capacity" number. If it shows 80 percent or higher and your phone lasts a full day, you do not need to replace it yet. If it shows 50 percent or lower, or if your phone shuts down without warning, replacement will restore normal performance.

Key Takeaways

  • Check your battery's maximum capacity in Settings > Battery > Battery Health & Charging — this number tells you how much charge it can hold compared to when it was new.
  • Replace your battery when your phone shuts down unexpectedly at 20 or 30 percent charge, or when it cannot last a full day of normal use.
  • Battery age alone does not determine replacement — a three-year-old battery that lasts all day is fine, but a one-year-old battery at 50 percent capacity should be replaced.
  • Apple's mail-in battery service costs between $69 and $99 depending on your model, and takes five to seven business days plus shipping time.
  • Third-party repair shops often charge $30 to $60 and can complete the work the same day, but quality varies and you lose water resistance if the seal is not properly resealed.

What happens inside your battery as it ages

iPhone batteries use lithium-ion chemistry. Each time you charge and discharge, the chemical compounds inside degrade slightly. After hundreds of cycles, the battery cannot hold as much charge. This is not a defect — it is how the chemistry works, and every rechargeable battery does this.

Apple built a safety feature called battery health management into iOS 13 and later. When your battery's health drops below a certain point, iOS slows down your processor to reduce power demand and prevent unexpected shutdowns. This slowdown is why an old iPhone feels sluggish. You can turn off this feature in Settings > Battery > Battery Health & Charging, but doing so means your phone will shut down without warning when the battery cannot deliver the power the processor needs.

The slowdown is temporary — replacing the battery restores full speed because the new battery can deliver the power your processor demands.

Signs your battery needs replacement now

Unexpected shutdowns are the clearest signal. If your iPhone turns off at 20 or 30 percent charge and then turns back on when you plug it in, the battery cannot deliver the current your phone needs, even though it still has charge stored. This will get worse over time.

A battery that drains visibly while you watch — losing 5 or 10 percent per hour while the phone is in your pocket — also signals replacement time. Normal drain is 1 to 3 percent per hour depending on what apps are running in the background.

Swelling is rare but serious. If your iPhone feels thicker, the screen is lifting away from the body, or the back is bulging, the battery is swelling and can damage other components or catch fire. Stop using the phone and take it to Apple or a repair shop when ready. Do not try to replace it yourself.

Apple's battery replacement service

Apple replaces batteries at Apple Stores and through mail-in service. The cost is $69 for iPhone 14 and earlier models, and $99 for iPhone 15 and later. The price does not change based on how old your phone is or how degraded the battery is.

At an Apple Store, the process takes about an hour if you have an appointment, or longer if you walk in. Apple will run diagnostics to confirm the battery is the problem, replace it, and test the phone before you leave. Your phone keeps its original serial number and water resistance rating.

Mail-in service works through Apple's website. You start a service request, print a shipping label, and send your phone to Apple. The turnaround is usually five to seven business days, not counting shipping time. You lose access to your phone during this period, so back up your data first.

Third-party repair shops and their trade-offs

Independent repair shops and chains like iFixit, Best Buy's Geek Squad, and local phone repair stores typically charge $30 to $60 for battery replacement and can often do it the same day or next day. The lower cost and faster turnaround appeal to many people.

The main trade-off is water resistance. iPhones are sealed with adhesive around the battery compartment. When a third-party shop opens the phone, they remove this seal. If they do not reapply it correctly, water can seep into the phone later. Some shops use new adhesive; others reuse the old seal. Ask before you hand over your phone.

Quality also varies. A shop that has replaced hundreds of batteries will do the work carefully. A shop that does it once a month may damage the display connector or other components while opening the phone. Check reviews on Google Maps or Yelp for that specific location, not the chain as a whole.

How to extend your current battery's life

Keep your phone between 20 and 80 percent charge when possible. Charging from 0 to 100 percent every day stresses the battery more than smaller, partial charges. If you charge overnight, enable Optimized Battery Charging in Settings > Battery > Battery Health & Charging. This feature learns your charging patterns and slows charging to 80 percent until you need the phone, then finishes the last 20 percent closer to when you wake up.

Avoid heat. Batteries degrade faster at high temperatures. Do not leave your phone in a hot car, in direct sun, or in a pocket against your body for hours. A cool environment extends battery life.

Turn off background app refresh for apps you do not need constant updates from. Go to Settings > General > Background App Refresh and toggle off apps that drain power without adding value to your day.

These steps slow battery aging but do not stop it. You will still need replacement eventually — they just buy you more time.

Deciding between Apple and a third-party shop

Choose Apple if you want a may provide that the water seal will be reapplied correctly, if you do not mind waiting a week, or if you want the work documented in your phone's service history. The higher cost buys you certainty.

Choose a third-party shop if you need the work done quickly, if cost matters more than speed, and if you can find a shop with strong reviews for battery replacement specifically. Ask them directly whether they reapply the water-resistant adhesive and what brand they use.

Do not use a shop that cannot answer these questions or that seems rushed. A battery replacement takes 30 to 45 minutes if done carefully. If a shop promises 15 minutes, they are cutting corners.

Frequently Asked Questions

Can I replace my iPhone battery myself?

Technically yes, but it is difficult and risky. You need a heat gun or hair dryer to soften the adhesive, special tools to pry open the phone without damaging the screen, and a steady hand. If you slip, you can break the display connector or puncture the battery, which can catch fire. Unless you have done this before, a professional replacement is safer and not much more expensive than the tools.

Will replacing the battery fix my slow iPhone?

If your slowness is caused by battery health management — which you can check in Settings > Battery > Battery Health & Charging — then yes, a new battery will restore full speed. If your phone is slow for other reasons (too many apps, old iOS version, storage full), the battery replacement will not help. Check your battery health first.

How long does a replacement battery last?

A new battery will retain 80 percent capacity after 500 charge cycles, just like the original. If you charge your phone once a day, that is roughly 18 months. If you charge it twice a day, it is about nine months. The actual lifespan depends on how you use and charge your phone, not on the replacement itself.

Does Apple charge different prices for different iPhone models?

Yes. iPhone 14 and earlier models cost $69. iPhone 15 and iPhone 15 Pro cost $99. iPhone 15 Pro Max costs $99. Prices may vary slightly by region. Check Apple's website for your specific model before you book an appointment.

What should I do if my battery is swelling?

Stop using the phone when ready and take it to Apple or a repair shop the same day. A swelling battery can damage the display, the logic board, or catch fire. Do not try to replace it yourself or wait for an appointment. Call ahead so they know you are coming with a potentially hazardous device.