Your iPhone battery degrades over time, and you'll notice it through slower performance, unexpected shutdowns, or a battery health reading below 80 percent

iPhones use lithium-ion batteries that lose capacity with every charge cycle. After about 500 full charge cycles—roughly one to two years of normal use—most iPhone batteries drop to 80 percent of their original capacity. You don't have to wait for catastrophic failure. Replacing a battery before it becomes unreliable is cheaper and less disruptive than dealing with a phone that shuts down mid-call or won't hold a charge through the morning.

The clearest signal is checking your battery health directly in Settings. On any iPhone running iOS 16.1 or later, go to Settings > Battery > Battery Health & Charging and look at the "Maximum Capacity" percentage. If it reads below 80 percent, your battery is genuinely worn. If it reads 80 percent or higher but your phone still drains fast or shuts down unexpectedly, the battery may still be the culprit—battery health doesn't always predict real-world performance.

Key Takeaways

  • Check your actual battery health in Settings > Battery > Battery Health & Charging; anything below 80 percent capacity means the battery is degraded and worth replacing.
  • Unexpected shutdowns, rapid drain even after a full charge, and slow performance under load are all signs a replacement will help, even if health reads higher than 80 percent.
  • Apple's battery replacement costs between $69 and $99 depending on your model, and takes one to two hours at an Apple Store or authorized repair shop.
  • Third-party repair shops often charge less but may use non-Apple batteries, which carry different warranties and may not integrate fully with iOS battery reporting.
  • If your phone is under warranty or covered by AppleCare+, battery replacement is free if health has dropped below 80 percent.

How to read your battery health number

The Battery Health & Charging screen shows two pieces of information: Maximum Capacity and Peak Performance Capability. Maximum Capacity is the one that matters for deciding whether to replace. It tells you what percentage of the battery's original charge it can still hold. A reading of 85 percent means the battery can now store 85 percent of what it could when new.

Peak Performance Capability describes whether iOS is throttling your processor to protect the battery. If it says "Normal," your phone is running at full speed. If it says "Reduced" or mentions "performance management," iOS has slowed your processor because the battery can no longer deliver the power the phone needs at full speed. This slowdown is temporary—it lifts once you replace the battery.

A battery at 79 percent capacity is worn enough that Apple will replace it for free if you have AppleCare+, or at the standard service price if you don't. A battery at 85 percent is still under the threshold Apple considers "degraded," but if your phone is shutting down or draining visibly faster than it did six months ago, the battery is likely the cause even if the percentage is higher.

Physical signs that replacement is overdue

Unexpected shutdowns are the most urgent signal. If your iPhone powers off at 20 percent battery, 40 percent, or even higher, the battery can no longer deliver the current the phone demands. This is a safety feature—the phone shuts down rather than risk damage. It means the battery is failing faster than the health percentage suggests, and replacement will restore normal operation.

Rapid drain is another clear sign. If your phone loses 20 percent battery in an hour of light use, or won't make it through a full day on a single charge when it used to, the battery is losing capacity. This is different from a software bug draining power—if drain is consistent across different apps and usage patterns, the battery itself is the problem.

Slow performance under load—lag when opening apps, stuttering video, or the phone getting warm during normal use—can also point to battery age. When a battery weakens, iOS throttles the processor to keep power draw stable. You'll notice this most when doing demanding tasks like gaming, video recording, or running multiple apps at once.

Apple Store replacement versus third-party repair

Apple charges $69 for an iPhone 15 or 16 battery, $79 for an iPhone 13 or 14, and $99 for older models like the iPhone 12 or earlier. The price depends on the model, not the condition of your current battery. Replacement takes one to two hours at an Apple Store or Apple Authorized Service Provider. You can book an appointment online or walk in, though walk-ins may have longer wait times.

Apple uses genuine Apple batteries and replaces them under a 90-day limited warranty. The replacement battery itself is not covered by AppleCare+ (the service is, but not the part), so you pay the full price unless your phone is still under the original one-year limited warranty and the battery has dropped below 80 percent capacity.

Third-party repair shops—independent technicians or chains like uBreakiFix—often charge $40 to $60 for the same service. They may use non-Apple batteries, which are cheaper but may not report battery health to iOS, and may not carry the same warranty. Some third-party batteries work flawlessly; others fail within months. The trade-off is lower upfront cost against less certainty about longevity and full integration with your phone's software.

What happens if you ignore a failing battery

A degraded battery won't suddenly explode or catch fire under normal use. Lithium-ion batteries are designed to fail safely. What will happen is increasing inconvenience: more frequent unexpected shutdowns, shorter time between charges, and performance slowdowns that make the phone feel sluggish. You'll also notice the battery percentage jumping erratically—it might show 30 percent, then drop to 5 percent a moment later, because the battery can no longer accurately report its charge level.

If the battery fails completely, your phone won't turn on at all until you plug it in, and it may not hold a charge even while plugged in. At that point, replacement becomes urgent rather than preventive. Waiting until that happens doesn't save money—you still pay the same service fee, but you've lost access to your phone for a day or two while waiting for the appointment.

AppleCare+ and warranty coverage

If you have AppleCare+ on your iPhone, battery replacement is free as long as the battery health has dropped below 80 percent capacity. You don't pay the $69 to $99 service fee. AppleCare+ also covers accidental damage, hardware failures, and theft, so if you're already paying for it, battery replacement is one of the benefits included.

If you don't have AppleCare+ and your phone is still within the original one-year limited warranty, Apple will replace the battery at no charge only if it has degraded below 80 percent capacity. Once the one-year warranty expires, you pay the standard service fee regardless of battery health.

Check your coverage status in Settings > General > About, or by visiting Apple's coverage checker at support.apple.com. Enter your serial number or IMEI to see whether your phone is still under warranty or covered by AppleCare+.

Preparing for your replacement appointment

Back up your iPhone before you go in. Apple doesn't erase your phone during a battery replacement, but it's standard practice to have a backup in case something unexpected happens. Use iCloud or a computer with Finder (on Mac) or iTunes (on Windows) to create a full backup.

Bring your phone and a form of ID. If you're using AppleCare+ or a warranty, bring proof—your receipt, AppleCare+ documentation, or the email confirmation from your Apple account. If you're paying out of pocket, bring a payment method. The appointment usually takes one to two hours, though it can be longer if the store is busy.

You don't need to erase your phone or sign out of your Apple ID before the appointment. The technician will handle the battery swap without touching your data. Your phone will be exactly as you left it when you pick it up.

Frequently Asked Questions

Can I replace my iPhone battery myself?

You can, but it's not straightforward. iPhones are glued together, and opening one requires heat, prying tools, and patience. If you slip, you can damage the screen, logic board, or other components. Apple and most repair shops recommend professional replacement. If you want to try it yourself, watch a full teardown video for your specific model first—the process varies significantly between models.

Will a new battery make my old iPhone feel fast again?

Yes, if your slowness is caused by battery degradation. iOS throttles the processor when the battery is weak, so replacing the battery removes that throttle and restores full speed. If your slowness is caused by storage being full or too many background apps, a new battery won't fix it.

How long does a replacement battery last?

A new Apple battery should last 500 to 1,000 charge cycles before dropping below 80 percent capacity again. That's typically two to three years of normal daily use. The exact lifespan depends on how often you charge, whether you let the battery drain completely, and how hot your phone gets during use.

What if my iPhone is too old to find a battery for?

Apple carries batteries for iPhones back to the iPhone 6s. For older models, third-party repair shops may still have batteries in stock, though availability varies. If no battery is available, replacement isn't an option, and you'd need to consider upgrading to a newer phone.

Does cold weather affect battery health readings?

Yes. Battery health readings are most accurate when your phone is at room temperature. Cold weather temporarily reduces battery capacity and can make the health percentage read lower than it actually is. If you check your battery health in a cold environment, wait for your phone to warm up and check again before deciding to replace it.