iPhone (iOS) · Troubleshooting
Diagnose Battery Wear and Charging Behavior
Battery Health & Charging shows your battery's Maximum Capacity as a percentage of its original capacity, its Peak Performance Capability status, and charging optimization options — the key diagnostic info for battery-related complaints.
How to open Battery Health & Charging
- Open Settings → Battery → Battery Health & Charging.
- Check the Maximum Capacity percentage.
- Review the Peak Performance Capability status underneath it.
- Turn on Optimized Battery Charging if you want to slow long-term wear.
What you should know
- Maximum Capacity estimates how much charge the battery can hold compared to when new.
- Peak Performance Capability shows whether the battery can currently support full performance without unexpected shutdowns.
- Optimized Battery Charging slows charging past 80% when it predicts you won't need a full charge soon, to reduce wear.
- A recommendation to service the battery appears here automatically once capacity drops significantly.
All rechargeable batteries wear down with normal use over time — a declining Maximum Capacity percentage is expected aging, not necessarily a defect.
Why it matters
Battery complaints — 'my phone dies too fast' or 'it shuts off randomly' — are among the most common iPhone support issues, and this screen is the actual diagnostic source of truth rather than guesswork. It's also how you know objectively whether a battery replacement is worth pursuing instead of just living with reduced battery life.
Best practices
- Turn on Optimized Battery Charging if the phone is regularly plugged in overnight, to slow long-term capacity loss.
- Avoid letting the battery repeatedly drain to 0% or sit at 100% for extended periods when avoidable.
- Consider a battery service once Maximum Capacity drops meaningfully below 80%, especially if you notice unexpected shutdowns.
Common problems and fixes
- Maximum Capacity shows a lower number than expected for the phone's age
- This can be normal for heavy daily use, but if it's unusually low for a newer phone, Apple may offer a battery service option — check eligibility on the same screen.
- Phone shuts down unexpectedly even with charge remaining
- Check Peak Performance Capability status here — if performance management has been applied, a battery replacement typically resolves the unexpected shutdowns.
Tips and tricks
- Turn off Optimized Battery Charging temporarily before a trip if you need a full, fast charge on a predictable schedule.
Frequently asked questions
What's considered a 'normal' Maximum Capacity percentage?
Apple designs the battery to retain up to 80% of its original capacity at 1,000 complete charge cycles under normal conditions, so numbers in that range at that usage level are expected, not faulty.
Does using Optimized Battery Charging slow down how fast the phone charges?
It can delay finishing the last portion of a charge past 80% when it's confident you won't need it right away, but it's designed to still have the phone fully charged by your typical usage time.
Related settings
- BatteryThe Battery screen shows your battery's current health and charging behavior, breaks down which apps used the most power recently, and includes Low Power Mode for stretching a low charge further.
- Diagnostic LogEvery app crash or system hang on iPhone generates a diagnostic log you can view directly on the device, useful for troubleshooting a misbehaving app yourself or sharing details with a developer or support team.
- Software UpdateSoftware Update keeps iOS current with the latest security fixes, features, and app compatibility. You can update wirelessly, overnight while charging, or via a computer.
More Troubleshooting guides for iPhone (iOS)
- Reset iPhoneReset options let you fix persistent software issues by resetting specific settings (like network or keyboard dictionary) or fully erase the device back to factory defaults.
- Analytics & ImprovementsAnalytics & Improvements controls whether your iPhone automatically sends anonymized crash reports and usage analytics to Apple, and optionally to third-party app developers, to help diagnose problems and improve software.
- Recovery Mode & RestoreRecovery Mode is a special startup state used with a computer running Finder (or iTunes on older systems) to reinstall or restore iOS when an iPhone is frozen, stuck on the Apple logo, or won't update normally.
- Force Restart & Shut DownA force restart or full shut down can resolve a frozen or unresponsive iPhone using a physical button sequence, without needing to reach Settings at all.
- Erase All Content and SettingsErase All Content and Settings permanently deletes everything on the iPhone, including apps, photos, settings, and accounts, restoring it to an out-of-box state, distinct from resetting individual settings categories.
- DFU Mode RestoreDevice Firmware Update (DFU) Mode is the lowest-level restore state available on iPhone, used when the device won't respond to a force restart or standard Recovery Mode, typically requiring a computer with Finder or iTunes.