Replace your iPhone battery when it no longer holds a full day of normal use, when the phone shuts down unexpectedly at 20–30% charge, or when the battery health drops below 80%

Your iPhone battery degrades over time because lithium-ion cells lose capacity with every charge cycle. A new iPhone battery is rated for about 500 full charge cycles before it reaches 80% of its original capacity. After that point, the battery still works, but it holds less charge and drains faster. You can check your battery's current health in Settings > Battery > Battery Health & Charging, where Apple shows you the maximum capacity as a percentage.

The most practical sign you need a replacement is when your phone no longer lasts through a normal day of use. If you're charging twice a day when you used to charge once, or if the phone dies before evening, that's a clear signal. Some people notice the phone feels sluggish at the same time—that's because iOS automatically reduces performance on degraded batteries to prevent unexpected shutdowns, a feature Apple calls performance management.

Key Takeaways

  • Check your battery health percentage in Settings > Battery > Battery Health & Charging; anything below 80% means the battery is aging normally and may soon need replacement.
  • Unexpected shutdowns at 20–30% charge, even when the phone shows battery remaining, are a sign the battery can no longer deliver the power your phone needs.
  • If your iPhone no longer lasts a full day of normal use, battery replacement will restore the phone to near-original performance and lifespan.
  • Apple's official 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 can affect warranty coverage and long-term reliability.

Battery Health Below 80% Means Replacement Is Coming Soon

When your battery health drops to 80%, Apple considers it officially degraded. At this point, the battery still works for most people, but you're entering the zone where replacement becomes a reasonable choice. Battery health between 80% and 70% is the sweet spot for deciding: the battery is noticeably weaker, but you still have time before it becomes frustrating.

Below 70% health, most people notice a real difference in daily use. The phone may not last through a full workday, and you'll find yourself hunting for a charger more often. At 50% health or lower, replacement is usually urgent—the battery can't reliably power the phone through normal activities.

Keep in mind that battery health percentage doesn't tell the whole story. A battery at 85% health might still feel fine if you use your phone lightly, while one at 75% health might feel weak if you use it heavily. The percentage is a guide, not a rule.

Unexpected Shutdowns at High Battery Percentage

If your iPhone shuts down suddenly when the battery shows 20%, 30%, or even 40% remaining, the battery is failing. This happens because the battery can no longer deliver the power surge your phone needs during peak use—like opening a camera app or running a game. The phone's safety system shuts it down rather than risk damage.

This is different from normal battery drain. Normal drain means the percentage slowly ticks down. Unexpected shutdowns mean the battery voltage has dropped so far that the phone can't operate, even though chemical energy remains in the cell. Restarting the phone usually works because the restart uses less power, but the problem will return.

Unexpected shutdowns are the most urgent sign that you need a replacement. They make the phone unreliable for calls, navigation, or any task where you can't afford a sudden restart.

Performance Slowdown Tied to Battery Age

If your iPhone feels noticeably slower than it used to, and the battery health is below 80%, the slowdown is likely intentional. Apple's performance management feature reduces CPU speed on older batteries to prevent unexpected shutdowns. This is a safety feature, not a bug, but it makes the phone feel sluggish.

You can check whether performance management is active in Settings > Battery > Battery Health & Charging. If you see a message saying "Peak Performance Capability," it means the feature is on. Replacing the battery will restore the phone's full speed because the new battery can deliver the power the processor needs.

Some people disable performance management to get speed back, but this increases the risk of unexpected shutdowns. Battery replacement is the proper fix.

How Long an iPhone Battery Typically Lasts

Most iPhone batteries reach 80% health after about two to three years of normal use. This timeline varies based on how you charge and use the phone. Frequent fast charging, leaving the phone plugged in overnight, and using it in hot environments all speed up degradation. Lighter use and cooler storage slow it down.

If you replace your battery at 80% health, you're looking at another two to three years before the new battery reaches the same point. This means a battery replacement can extend your phone's useful life by several years without buying a new device.

iPhones older than four years almost always have batteries below 80% health. If you're still using an older model and haven't replaced the battery, replacement is worth considering even if the phone otherwise works fine.

Apple Store Versus Third-Party Repair Shops

Apple's official battery replacement costs $69 for iPhone 15 and newer models, and up to $99 for older models. The service takes one to two hours at an Apple Store or Apple Authorized Service Provider. Apple uses genuine batteries and maintains your warranty coverage.

Third-party repair shops often charge $30 to $60 for the same service. The trade-off is that they may use non-Apple batteries, which can affect long-term reliability and may void your warranty if you have AppleCare+. Some third-party shops use quality aftermarket batteries; others use cheaper ones that degrade faster.

If your phone is still under warranty or you have AppleCare+, Apple's service is usually the safer choice. If your phone is older and out of warranty, a reputable third-party shop can save money without much risk. Check reviews and ask whether they use Apple-certified batteries before you commit.

What to Do Before Your Battery Fails Completely

Don't wait until your phone shuts down unexpectedly to schedule a replacement. Check your battery health now—it takes 30 seconds. If it's below 80%, you have time to plan the replacement without urgency.

Back up your phone before you take it in for service. Most battery replacements don't touch your data, but backups protect you if something goes wrong. Use iCloud or connect to a computer and use Finder (on Mac) or iTunes (on Windows).

If you use your phone for work or navigation, schedule the replacement when you can be without it for a few hours. Apple Stores often have same-day appointments, but during busy seasons you may need to book ahead. Third-party shops are usually faster but may not have appointments available.

Frequently Asked Questions

Can I replace my iPhone battery myself?

Apple does not sell batteries to consumers for self-replacement, and opening your iPhone yourself voids the warranty and risks damaging the water-resistance seal. Some third-party shops sell battery kits with tools, but this requires technical skill and carries real risks of breaking the screen or logic board. Professional replacement is safer and often cheaper than the cost of fixing mistakes.

Will a new battery make my old iPhone feel like new?

A new battery will restore full-day battery life and remove performance slowdown caused by battery degradation. It won't update the processor or add new features, so the phone will still be the same model. But if slowness was the main complaint, you'll notice a real difference.

How do I know if my battery health reading is accurate?

Apple's battery health percentage is accurate for the current state of the battery. It measures the maximum charge the battery can hold compared to when it was new. The percentage can fluctuate slightly based on temperature and recent usage, but if you check it multiple times over a few days, you'll see the same number.

What happens if I ignore a degraded battery?

The battery will continue to lose capacity and eventually become unreliable. You'll experience more frequent unexpected shutdowns, shorter battery life, and possible performance slowdown. The phone will still work, but it becomes less dependable. Waiting too long can also damage the battery itself, making replacement more expensive if the battery swells or leaks.

Does cold weather affect when I should replace my battery?

Cold temporarily reduces battery performance—your phone may shut down at a higher percentage in winter than in summer. This is normal and reversible; the battery recovers when it warms up. However, if your phone shuts down unexpectedly even in warm conditions, the battery itself is failing and needs replacement regardless of season.