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Open Settings > Battery > Battery Health (or Battery Health & Charging) and check two items: Maximum Capacity and Peak Performance Capability. A “significantly degraded” warning, repeated unexpected shutdowns, or battery life that no longer meets your needs are the strongest reasons to arrange a service evaluation. A percentage by itself is not a universal replacement deadline.
Start with the iPhone’s built-in battery report
Apple’s battery screen is the quickest way to determine whether the battery is aging and whether iOS can still deliver the power the phone needs. The labels vary slightly by iOS version, but the path is:
- Open Settings.
- Tap Battery.
- Tap Battery Health or Battery Health & Charging.
- Read Maximum Capacity and Peak Performance Capability.
Read the exact wording, not just the percentage. The message beneath the headings can tell you whether iOS considers the battery capable of supporting normal peak power, whether performance management has been applied, or whether the health estimate needs attention.
If your iPhone cannot display reliable battery information, Apple says the information shown may not be accurate. Arrange a diagnostic check rather than making a replacement decision from an unverified percentage.
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What Maximum Capacity means
Maximum Capacity compares the battery’s current estimated capacity with its capacity when new. As that estimate falls, the phone may provide fewer hours between charges. It is an estimate, not a direct measurement of how many hours your particular iPhone will last: screen brightness, cellular reception, apps, temperature, charging habits and software activity all affect runtime.
Two phones showing the same percentage can therefore feel very different. One owner may still finish a normal day comfortably, while another may need several top-ups because of heavy camera use, weak cellular coverage or long periods of navigation. The useful question is whether the capacity change has become inconvenient for your own routine.
What Peak Performance Capability means
Peak Performance Capability indicates whether the battery can supply the peak power the iPhone may request. An aged battery can be unable to deliver a short burst of power even when its remaining capacity appears adequate. iOS may then apply performance management, and an aging battery can be associated with unexpected shutdowns.
When the report says, “Your battery is currently supporting normal peak performance,” Apple is telling you that the battery is presently supporting normal peak performance. That message alone is not a reason to replace the battery. It does not promise that the battery will last as long as it did when new, because peak-power delivery and total stored capacity are different properties.
How to interpret the result
| What you see | What it means | Practical next step |
|---|---|---|
| Normal peak-performance message and acceptable runtime | The battery is supporting the phone’s expected peak-power needs, and you have not identified a meaningful usability problem. | Keep using the iPhone. Recheck the report if runtime or shutdown behavior changes. |
| Normal message but very short runtime | Capacity may have declined enough to affect your day even though peak-power delivery remains normal. | Compare the runtime with your actual needs and request a model-specific service estimate if charging has become disruptive. |
| Unexpected shutdowns or performance management | The battery may not be sustaining peak power consistently. | Save important data and arrange a battery diagnostic or service evaluation. |
| “Your battery’s health is significantly degraded. An Apple Authorised Service Provider can replace the battery to restore full performance and capacity.” | Apple considers the battery health significantly degraded. Apple says this notice does not itself indicate a safety issue, although battery and performance problems may be more noticeable. | Arrange service if you want to restore capacity and performance. Ask for an estimate for your exact model and region. |
| Battery-health information cannot be verified or may be inaccurate | The displayed estimate should not be treated as a dependable diagnosis. | Have Apple or a qualified provider inspect the phone. |
When Apple’s 80% figures help—and when they do not
Apple’s current support guidance, checked in October 2026, gives design expectations measured under ideal conditions:
- iPhone 14 models and earlier: 80% of original capacity after 500 complete charge cycles.
- iPhone 15 models: 80% of original capacity after 1,000 complete charge cycles.
These figures describe how Apple designs the batteries to perform under the stated conditions. They are not a promise about every individual phone and not an automatic replacement trigger. Actual capacity depends on how the device is used and charged, along with environmental and other operating conditions.
A phone above 80% can still be inconvenient if it no longer lasts through your day. A phone below 80% may remain usable if its runtime and performance meet your needs. Conversely, a phone at a seemingly acceptable percentage may deserve inspection if it shuts down, reports performance management or cannot provide trustworthy health information.
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Symptoms that justify a service check
Runtime has become impractical
If you need several top-ups to get through normal use, compare the change with your own previous experience rather than with a number found online. Note which activities drain the phone, whether the drain occurs while idle, and whether the problem began after a software update or a change in coverage. Those observations help a technician distinguish battery aging from an app, signal or software problem.
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Describe the pattern clearly: for example, whether the phone loses charge mainly during video, camera or navigation use, or whether it drops unusually quickly while sitting unused. This does not prove which component is at fault, but it gives the service provider useful context before inspection.
The iPhone shuts down unexpectedly
Unexpected shutdowns are a power-delivery symptom worth investigating, particularly when they occur at moderate charge percentages, in cold conditions or during demanding tasks. A battery replacement may solve the problem, but a diagnostic check is appropriate because charging hardware, software and other components can produce similar behavior.
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Record how often the shutdown happens and what the battery percentage showed immediately beforehand. If the phone is unreliable, back up important information before arranging service and avoid treating a single restart as proof that a replacement is required.
Performance feels reduced
Open the Peak Performance Capability section and read any notice about performance management. A degraded battery may be unable to meet peak-power demands, so iOS can manage performance to reduce the chance of another shutdown. Do not disable or work around a protection feature before identifying the battery condition and the underlying cause.
Performance concerns can overlap with software or other hardware issues. Tell the provider what feels slower, when it started and whether the behavior appears alongside shutdowns or an explicit battery message.
The phone reports a significantly degraded battery
Apple’s degraded-health notice is the clearest built-in signal to arrange service. Apple states that the notice is not, by itself, a safety warning; it means the battery and performance experience may be worse and that replacing the battery can restore full performance and capacity.
The notice is therefore a service recommendation, not an instruction to discard the phone immediately. Ask for a model-specific estimate and let the provider inspect the device, especially if it has impact damage, liquid exposure or another fault that could affect the repair.
Special case: iPhone 11, 11 Pro and 11 Pro Max recalibration
Battery-health reporting on the iPhone 11, iPhone 11 Pro and iPhone 11 Pro Max can recalibrate over regular charge cycles. Apple says the process may take a few weeks. During that period, the Maximum Capacity estimate and related messages may change as the system updates its calculation.
If your iPhone 11 family device explicitly shows that recalibration is in progress, continue normal use and charging when practical, then review the report after the stated period. Avoid treating an interim percentage as a final diagnosis. If the report remains unavailable, repeatedly changes without resolving, or the phone has serious runtime or shutdown symptoms, arrange a check rather than waiting indefinitely.
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Recalibration is a reporting process; it is not evidence that the battery has suddenly recovered or failed. The practical action is to allow the calculation to complete when the phone remains usable, while escalating sooner if reliability or performance is materially affected.
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- Read the report. Record Maximum Capacity, the exact Peak Performance Capability message and any notice about verification, shutdowns or performance management.
- Match the report to your experience. Decide whether runtime, shutdowns or performance are materially affecting your normal use.
- Check for the iPhone 11 recalibration notice. If present, allow the process to run for the few weeks Apple describes before relying on the updated estimate, unless symptoms require earlier service.
- Choose a service route. Apple and Apple Authorized Service Providers offer in-person and mail-in options. If you choose a non-Apple repairer or DIY, verify model and part compatibility first.
- Back up before handing over the phone. Use your normal iCloud or computer backup, remove accessories you need to keep, and follow the provider’s instructions for preparing the device.
If the report is normal and your runtime is acceptable, there is no need to replace the battery simply to reach a particular percentage. If the report is degraded or the phone is no longer dependable, service is reasonable even when you do not know the exact cycle count.
Apple service: what to expect
Apple’s service process can be arranged in person or by mail. Apple says it must inspect the device to provide a personalized estimate. The final fee depends on the iPhone model and the inspection, and an Apple Authorized Service Provider may set its own fees. Because the title does not specify a model, country, warranty status or coverage plan, there is no single accurate price to quote.
When requesting an estimate, have the exact model (for example, the model generation and storage variant if requested), the country where service will occur, and any warranty or service-plan details available. Ask whether the quoted work is battery-only, what happens if inspection finds additional damage, and whether the repair is in person or shipped to a service center.
Do not treat an old online price, a quote for another iPhone generation or a third-party listing as your final cost. Regional fees and provider policies can change, and the inspection may identify work beyond the battery.
In-person service
In-person service lets a technician inspect the phone and explain findings before work begins. It is useful when the battery report is unavailable, the phone has suffered impact or liquid exposure, or you suspect a problem beyond the battery.
Bring the information you recorded from Battery Health and describe the symptoms. Confirm whether the provider can complete the work at that location or will send the device elsewhere, and ask when you can expect the estimate and completion.
Mail-in service
Mail-in service can be convenient when a store is not nearby. Follow the provider’s packaging and backup instructions exactly, and plan for the time your phone will be unavailable. Confirm how the provider handles activation locks, data privacy and return shipping before sending the device.
Keep tracking information and remove cases or accessories only as instructed. Do not ship the phone before you understand what information must be backed up and what the provider needs disabled for service.
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DIY replacement: only for a deliberate, model-specific choice
A do-it-yourself replacement is not a way to test whether the battery is bad; diagnosis should come first. If you explicitly choose DIY, buy a kit designed for your exact iPhone model and understand the repair risks. iFixit’s iPhone 15 guide identifies a replacement battery and adhesive as required and offers a kit containing the parts and tools. That information does not make the kit compatible with other iPhone generations, and product availability can change.
A kit is a parts-and-tools option, not a battery-health measurement device. It cannot tell you whether an app, charging component, software issue or other hardware fault is causing the symptoms. If the phone has a warning that its health information may be inaccurate, professional inspection is the more dependable first step.
Before ordering a kit
- Confirm the exact iPhone model and generation, not just the screen size or case fit.
- Check that the kit includes a battery, replacement adhesive and the tools required by the guide for that model.
- Read the current model-specific instructions from start to finish and identify steps involving fragile cables, seals or adhesive.
- Decide whether you can work safely with a powered lithium-ion battery and keep screws and connectors organized.
- Compare the complete cost, including tools, replacement parts and the possibility of damage, with the provider’s estimate.
Trade-offs versus professional service
| Consideration | Professional service | DIY |
|---|---|---|
| Diagnosis | Inspection can identify a battery fault or another hardware problem before replacement. | You must diagnose the problem and accept the risk of replacing the wrong part. |
| Parts and compatibility | The provider selects parts for the identified model and service path. | You must verify model-specific battery, adhesive and tool compatibility. |
| Skill and risk | A technician performs the disassembly and reassembly. | Opening the phone can damage cables, connectors, seals or the battery if handled incorrectly. |
| Price information | Apple requires inspection for a personalized estimate; authorized providers may set their own fees. | Up-front kit cost is visible, but tools, replacement parts and damage risk can add cost. |
| Support | Apple or the provider manages the repair process and explains available service. | You manage troubleshooting, parts, instructions and any follow-up repair. |
If you are unsure which model you have, cannot verify the part, or see swelling, damage or liquid exposure, do not open the phone. Arrange a professional inspection instead.
Independent reader supportYour contribution helps us test, update, and keep practical guides available for everyone.Common mistakes and how to avoid them
Replacing solely because the percentage is below a favorite threshold
Apple’s 80% figures are design expectations under ideal conditions, not an individual deadline. Use the report together with runtime, shutdown and performance symptoms.
Assuming a normal peak-performance message guarantees long battery life
Peak power and total capacity are different properties. The phone can support peak performance while still requiring more frequent charging than you find acceptable.
Ignoring the iPhone 11 recalibration message
During recalibration, the displayed estimate may not yet represent the final calculation. Allow the process to run for the period Apple describes, while seeking service sooner if the phone is unreliable.
Buying a generic kit without checking the model
Battery connectors, adhesive layouts and disassembly procedures vary by generation. A kit for one model is not evidence of compatibility with another.
Expecting a universal repair price
Model, location, inspection findings, warranty status and provider policy affect the final fee. Request a current estimate for your device rather than relying on an old price list or another model’s quote.
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Treating an inaccurate report as a diagnosis
If iOS warns that battery-health information may not be accurate, do not use the displayed percentage to justify a purchase. Have Apple or a qualified provider inspect the phone.
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Questions to record before contacting service
- What exact iPhone model and iOS version are installed?
- What Maximum Capacity percentage is shown, and what is the precise Peak Performance Capability message?
- How long does the phone last under your normal use, and what changed?
- Have unexpected shutdowns, overheating, swelling, drops or liquid exposure occurred?
- Is an iPhone 11-family recalibration notice present?
- Do you need in-person service, mail-in service or a model-specific DIY option?
Providing these details helps the service provider determine whether a battery replacement is appropriate or whether another fault needs attention first.
Frequently Asked Questions
How do I check my iPhone battery health?
Open Settings, tap Battery, then Battery Health or Battery Health & Charging. Read Maximum Capacity and Peak Performance Capability, including any warning beneath them.
What does Maximum Capacity mean on iPhone?
It is the battery’s current estimated capacity compared with its capacity when new. A lower estimate can mean fewer hours between charges, but it is not a direct prediction of your daily runtime.
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Arrange service when Apple reports that the battery’s health is significantly degraded, when unexpected shutdowns or performance management persist, or when runtime no longer meets your needs. Do not replace it solely because the percentage crosses an arbitrary threshold.
Is 80% battery health the replacement point?
No. Apple describes 80% after 500 complete cycles for iPhone 14 models and earlier, and 80% after 1,000 complete cycles for iPhone 15 models, under ideal conditions. These are design expectations, not universal deadlines.
What if my iPhone 11 says battery-health recalibration is in progress?
Apple says recalibration can take a few weeks of regular charge cycles. Continue normal use when practical and review the report afterward, but seek service sooner if the phone is unreliable or has serious symptoms.
How much does an iPhone battery replacement cost?
There is no universal price. Apple requires inspection for a personalized estimate, and the fee depends on model and inspection. Authorized providers may set their own fees, so ask for a current estimate in your region.
Should I replace the battery myself?
Only as a deliberate, model-specific choice. A DIY kit is not a diagnostic tool; verify the exact model, battery, adhesive and tools, and weigh repair skill, damage risk and total cost against professional service.
The Bottom Line
Check Maximum Capacity and Peak Performance Capability, then compare the report with your actual runtime and shutdown experience. A significantly degraded message or persistent reliability problem justifies a model-specific service estimate; a normal message and acceptable battery life do not require replacement simply to reach 80%.
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