Replace your iPhone battery when it drops below 80% health, or sooner if you notice your phone shutting down unexpectedly

Apple's battery health system shows you a percentage that tells you how much capacity your battery retains compared to when it was new. At 80% health, your battery still holds a decent charge, but Apple considers this the threshold where a battery replacement becomes worthwhile. Below 80%, your phone will drain faster, may struggle to power demanding apps, and could shut itself down even when the battery percentage display shows 20% or 30% remaining. That unexpected shutdown is the real problem—it means your battery can no longer deliver the power your phone needs, even though it still holds some charge.

You do not have to wait until 80% to replace the battery. If your phone is shutting down unexpectedly, draining in a few hours, or struggling to run apps you use every day, a replacement at 85% or 90% health makes sense. Battery health is one measure; how the battery behaves in your actual life is another.

Key Takeaways

  • Check your battery health percentage in Settings > Battery > Battery Health & Charging on any iPhone running iOS 16 or later.
  • Apple considers 80% health the point where replacement becomes practical, though you can replace sooner if your phone shuts down unexpectedly.
  • Unexpected shutdowns, rapid drain, or apps crashing are signs your battery cannot deliver power even if the percentage display shows charge remaining.
  • Battery health drops faster if you regularly charge to 100%, leave your phone in hot environments, or use it heavily while charging.

How to check your iPhone battery health percentage

Open Settings, tap Battery, then tap Battery Health & Charging. You will see a percentage labeled "Maximum Capacity"—that is your battery health. This number tells you what fraction of the battery's original capacity remains. A battery at 85% health holds 85% of the charge it held when new.

This feature is available on iPhone 6 and later running iOS 11.3 or newer. If you have an older iPhone or an older iOS version, you cannot see the percentage in Settings, but you can still have the battery replaced at an Apple Store or authorized repair shop.

Why 80% is Apple's replacement threshold

At 80% health, a battery has lost enough capacity that most people notice a real difference in daily use. Your phone drains noticeably faster, and if you use it heavily, you may not make it through a full day without charging. More importantly, the battery's ability to deliver power in short bursts—the power needed to run the camera, process photos, or handle a sudden spike in processor demand—starts to fail.

This is why iPhones sometimes shut down at 20% or 30% battery. The battery cannot push enough power to the phone's components all at once, even though it still holds charge. Apple set 80% as the point where this becomes a common problem for most users, not a rare edge case.

Signs your battery needs replacement before it reaches 80%

Unexpected shutdowns are the clearest sign. If your iPhone powers off when the battery shows 25% or higher, the battery is failing and should be replaced regardless of the health percentage. This shutdown protects the phone's components from damage, but it also makes the phone unusable.

Rapid drain is another signal. If your battery goes from 50% to 0% in two or three hours of normal use, or if a full charge only lasts a few hours, replacement may help. Keep in mind that background app refresh, location services, and screen brightness all affect drain, so compare your drain to how you used the phone when the battery was new.

Apps crashing or freezing during heavy use—gaming, video recording, or photo editing—can also point to a failing battery. These tasks demand a lot of power, and a weak battery cannot deliver it consistently.

What causes battery health to drop faster

Charging to 100% regularly wears the battery faster than charging to 80%. If you charge your phone every night and leave it plugged in, you are exposing the battery to stress. iPhones running iOS 15.1 or later have an Optimized Battery Charging feature that slows charging to 80% and waits to finish the last 20% until you typically wake up. Turning this on in Settings > Battery > Battery Health & Charging extends battery lifespan.

Heat is another major factor. Leaving your iPhone in a hot car, using it in direct sunlight for long periods, or using it while it charges all generate heat that degrades the battery faster. Lithium batteries lose capacity permanently when exposed to high temperatures.

Heavy use while charging—streaming video, gaming, or video calling while plugged in—combines heat and stress and wears the battery quickly. If you need to use your phone while charging, try to keep it in a cool environment.

Battery replacement costs and where to go

Apple charges a flat fee for out-of-warranty battery replacement. The cost varies by iPhone model but typically ranges from $50 to $70. If your iPhone is still under the one-year limited warranty or covered by AppleCare+, battery replacement is free if the health has dropped due to a manufacturing defect (not normal wear).

You can replace the battery at an Apple Store, an Apple Authorized Service Provider, or certain third-party repair shops. Apple Stores and Authorized Service Providers use genuine Apple batteries and offer a warranty on the replacement. Third-party shops may charge less but may not use genuine parts or offer the same warranty. Check the repair shop's reviews and ask whether they use genuine batteries before you commit.

Replacement usually takes one to three hours if you drop the phone off, or same-day if you make an appointment and wait. Some locations offer mail-in service if no store is nearby.

How to extend battery health and delay replacement

Enable Optimized Battery Charging in Settings > Battery > Battery Health & Charging. This feature learns when you typically charge your phone and slows charging to 80% until shortly before you wake up, reducing stress on the battery.

Keep your iPhone cool. Avoid leaving it in hot cars, direct sunlight, or enclosed spaces. If your phone gets warm during use, close apps and let it cool before charging.

Avoid letting the battery drain completely. Charging from 20% to 80% is easier on the battery than charging from 0% to 100%. If you can, charge more often and to a lower percentage.

Turn off background app refresh for apps you do not need to update constantly. Go to Settings > General > Background App Refresh and toggle off apps that drain the battery without adding value to your daily use.

Frequently Asked Questions

Is it safe to keep using my iPhone if the battery health is below 80%?

Yes, it is safe to use. The phone will not be damaged. However, you will notice faster drain and may experience unexpected shutdowns. If shutdowns are happening, replacement becomes practical rather than optional.

Will replacing the battery make my iPhone feel like new?

A new battery will restore charging speed and eliminate unexpected shutdowns, but it will not speed up the processor or improve performance in other ways. If your phone feels slow for reasons other than battery drain, the battery replacement alone will not fix that.

Can I replace the battery myself?

iPhones are difficult to open without damaging the screen or other components. Unless you have experience with phone repair, a professional replacement is safer and comes with a warranty. DIY replacement voids any remaining warranty and risks breaking the phone.

Does AppleCare+ cover battery replacement?

AppleCare+ covers battery replacement at no cost if the battery health drops due to a defect. Normal wear and tear—battery health dropping from regular use—is not covered, but you still get the standard out-of-warranty replacement fee instead of a higher accidental damage fee.

How long does a new iPhone battery last before it needs replacement again?

Apple designs batteries to retain 80% health after about 500 full charge cycles. A charge cycle is draining the battery from 100% to 0%, or the equivalent spread across multiple days. For most people, this means two to three years before the battery drops to 80% health, depending on how heavily you use the phone and how you charge it.