Where to find your battery health on iPhone
Apple built a battery health tool directly into every iPhone running iOS 11.3 or later. Open Settings, tap Battery, then tap Battery Health & Charging. You will see two numbers: your battery's maximum capacity as a percentage, and the peak performance capability.
Maximum capacity tells you how much charge your battery can hold compared to when it was new. A new iPhone battery is at 100%. After normal use over months or years, this number drops — that is expected and normal. Peak performance capability shows whether your phone is running at full speed or if iOS has slowed the processor to protect an aging battery.
This screen also shows you whether your battery needs service. If Apple's diagnostics detect a problem, you will see a message saying the battery may need service, along with a recommendation to visit an Apple Store or authorized repair shop.
Key Takeaways
- Your battery health is in Settings > Battery > Battery Health & Charging, and shows what percentage of original capacity remains.
- Maximum capacity naturally decreases over time; a battery at 80% after two years of normal use is performing as designed.
- Peak performance capability tells you whether iOS has slowed your processor to protect the battery, which happens automatically when capacity drops below a threshold.
- If you see a "battery may need service" message, the battery has a genuine fault and should be inspected by Apple or an authorized technician.
- Replacing an iPhone battery through Apple costs less than most repairs and often restores the phone to full speed if it was throttled.
What maximum capacity percentage actually means
Maximum capacity is not a prediction of how long your battery will last in a single day. It is a measure of how much total energy the battery can store right now, compared to the day it left the factory. A battery at 80% maximum capacity can still power your phone all day — it straightforward holds 20% less total charge than it did when new.
Apple considers 80% maximum capacity the threshold where a battery is still healthy. Most iPhones reach 80% after 500 full charge cycles — roughly two to three years of typical use. A charge cycle means draining the battery completely and charging it back to 100%, though it does not have to happen in one day.
Once capacity drops below 80%, your phone may show the "battery may need service" message, or you may straightforward notice the phone dies sooner than it used to. Neither means the battery is broken — it means the battery is aging normally and you have the option to replace it.
Understanding peak performance capability
Peak performance capability describes whether your iPhone is running at full processor speed. When you see "Peak Performance Capability: Normal," your phone is running as fast as it can. When you see "Peak Performance Capability: Reduced," iOS has automatically slowed down the processor.
iOS throttles the processor to prevent unexpected shutdowns. An aging battery cannot deliver power as quickly as a new one, so when the processor demands a sudden burst of power, an old battery may not be able to keep up. Instead of crashing, iOS slows the processor down so the battery can supply steady power. This is intentional protection, not a malfunction.
If your battery health is above 80% and you still see "Reduced" performance, the battery may have a fault. Tap the message to see more details, or visit an Apple Store to have the battery tested.
When to replace your iPhone battery
You do not have to replace your battery the moment it drops below 80%. Many people use iPhones with batteries at 70% or 60% capacity without problems. Replace the battery when one of these things happens: the phone shuts down unexpectedly even though the battery percentage shows charge remaining, the phone is throttled and you want full speed back, or Apple's diagnostics say the battery needs service.
Battery replacement through Apple costs between $50 and $80 depending on your iPhone model, and usually takes a few hours to a few days. If your phone is still under warranty or covered by AppleCare+, the replacement may be free. Third-party repair shops often charge less, but use parts that may not match Apple's quality standards.
If your battery is below 50% maximum capacity, replacement is usually worth the cost because the battery is genuinely old and may fail without warning. If your battery is between 80% and 50% and the phone works fine, you can wait until you notice a real problem.
How to read the battery health screen if it shows a warning
If the battery health screen shows "This iPhone has experienced an unexpected issue and the battery may need service," the battery has failed a diagnostic test. This does not mean the battery will stop working today, but it means the battery has a defect that will likely get worse. Apple recommends service.
You can continue using the phone while you arrange a replacement, but do not wait too long. A battery with a known fault can fail suddenly, and you may lose data if the phone shuts down without warning during a task. Schedule service within a week or two if possible.
If the message says "Unable to determine battery health," your phone cannot communicate with the battery properly. This is rare and usually means a hardware problem beyond the battery itself. Visit an Apple Store to have the phone diagnosed.
Steps to check battery health on older iOS versions
If your iPhone is running iOS 11.2 or earlier, the battery health tool does not exist. You can still see some battery information by opening Settings, tapping Battery, and looking at the battery percentage in the top right corner. This shows you current charge, not health.
To get a real picture of battery health on older iOS, you need a third-party app from the App Store that reads battery data, or you can visit an Apple Store and ask them to run a diagnostic. Apple's in-store diagnostic is free and takes a few minutes.
If your phone is running iOS 11.2 or earlier, consider updating to the latest iOS version your phone supports. Newer iOS versions include the battery health tool and often improve battery performance.
Why your battery health dropped faster than expected
If your battery dropped from 100% to 80% in less than a year, or you see rapid capacity loss month to month, a few things could be happening. Leaving your phone in a hot car or direct sunlight regularly damages batteries faster. Letting the battery drain completely to 0% and staying there for days also accelerates aging. Running demanding apps constantly — like games, video editing, or navigation — generates heat that wears the battery.
If you notice sudden drops in capacity (like 95% one week, 85% the next), the battery may have a fault. Take the phone to Apple or an authorized repair shop to have it tested. Genuine defects are sometimes covered under warranty even if the phone is out of the standard one-year period.
Normal aging is gradual. If your battery is dropping noticeably every few weeks, something is wrong and you should get it checked.
Frequently Asked Questions
Is 80% battery health bad?
No. Apple considers 80% the threshold where a battery is still healthy. Most iPhones reach 80% after two to three years of normal use. Your phone will still work fine at 80% — it straightforward holds 20% less charge than when new. You can wait to replace the battery until you notice the phone dying sooner than you want.
Can I improve my battery health?
No. Battery capacity loss is permanent and cannot be reversed by software updates, settings changes, or charging habits. Once a battery ages, only physical replacement restores capacity. You can slow future aging by avoiding heat, not letting the battery drain completely, and not running demanding apps constantly, but you cannot recover capacity already lost.
Why is my iPhone throttled if my battery is still above 80%?
If your battery shows above 80% capacity but the phone is throttled, the battery may have a fault that the health screen has not yet detected. Visit an Apple Store to have the battery tested. Alternatively, if you recently updated iOS, restart your phone — sometimes throttling persists briefly after an update and clears on restart.
Do I need AppleCare+ to replace my battery?
No. Battery replacement is available to anyone and costs $50 to $80 out of pocket. AppleCare+ covers battery replacement at no cost, but you do not need it. If your phone is still in the one-year limited warranty period and the battery is defective, Apple may replace it free even without AppleCare+.
What does "peak performance capability: normal" mean?
It means your iPhone is running at full processor speed with no slowdown. Your battery is supplying power fast enough that iOS does not need to throttle the processor. This is the normal state for phones with healthy batteries or new batteries.