How to Check iPhone Battery Health
iPhones have a built-in Battery Health screen that tells you exactly how worn out your battery is — but most people either do not know where it is or do not understand what the numbers mean. Learning to read your Battery Health is the single most useful diagnostic skill for iPhone owners. It tells you when to replace the battery, whether your phone is being CPU-throttled, and roughly how much life is left before performance degrades. Here is everything you need to know.
How to find Battery Health on your iPhone
Open Settings > Battery > Battery Health & Charging. This screen is hidden from the main Battery screen and a lot of people never find it. It shows three key pieces of information: Maximum Capacity (your battery’s current capacity as a percentage of its original design), Peak Performance Capability (whether iOS is throttling CPU to prevent shutdowns), and optimized charging settings. All iPhones running iOS 11.3 or newer have this feature.
What ‘Maximum Capacity’ actually means
Maximum Capacity is the amount of charge your battery can currently hold, expressed as a percentage of what the battery could hold when it was brand new. A new iPhone starts at 100 percent. After roughly 500 complete charge cycles (about 18-24 months of typical use), the battery degrades to around 80 percent. A phone at 85 percent Maximum Capacity will hold 85 percent as much charge as it did when new. So a phone that once ran from morning to evening on a single charge will now run from morning to late afternoon. At 80 percent you will notice meaningful runtime loss. At 70 percent the phone feels genuinely underpowered.
The dreaded ‘Peak Performance Capability’ warning
Below Maximum Capacity is a section called Peak Performance Capability. On a healthy battery it will say ‘Your battery is currently supporting normal peak performance.’ On a degraded battery, iOS may insert a warning like ‘This iPhone has experienced an unexpected shutdown because the battery was unable to deliver the necessary peak power. Performance management has been applied to help prevent this from happening again.’ Translation: iOS is throttling your CPU to protect against sudden shutdowns. This makes the phone noticeably slower. A battery replacement removes the throttling immediately.
When you should replace the battery
General guidelines based on what we see at Indiana Phones: above 85 percent, no replacement needed unless you have a specific complaint. Between 80-85 percent, replacement is optional — you will notice some runtime loss but the phone still performs normally. Below 80 percent, replacement is strongly recommended. Apple’s own guidance says a battery at this level is ‘significantly degraded’. Below 70 percent, replacement is urgent — you will be experiencing slowdowns, random shutdowns, and substantial runtime loss.
Battery cycle count — the other metric that matters
iOS 17 added a Cycle Count display for newer iPhones (iPhone 15 and later). One charge cycle equals charging from 0 to 100 percent — not a single plug-in, but a complete discharge/charge equivalent spread over multiple plug-ins. Apple rates iPhone batteries for 1000 cycles at 80 percent+ capacity on iPhone 15 and newer, and 500 cycles on older models. If your phone shows 800+ cycles on an older model, the battery is well past its prime regardless of what the Maximum Capacity percentage says.
How to preserve battery health longer
Avoid extreme temperatures — do not leave your phone in a hot car or in direct sunlight for hours. Avoid charging to 100 percent and staying plugged in for hours at a time — modern iPhones have an ‘Optimized Battery Charging’ feature that helps with this. Do not routinely let the battery drop to zero percent. Use genuine or MFi-certified chargers rather than bargain-bin USB bricks that can deliver erratic voltage. None of these extend the battery forever — lithium-ion batteries are consumables — but they slow the degradation significantly.
Free battery check at Indiana Phones
If you are unsure whether your battery needs replacement, bring your iPhone to Indiana Phones in Pacific Beach. We test battery health for free, explain exactly what you are seeing, and give you honest advice about whether replacement is worth it. No pressure, no sales pitch. Call (619) 577-3065 or walk in to 1630 Grand Ave.
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Frequently Asked Questions
At what battery health percentage should I replace my iPhone battery?
Below 80 percent Maximum Capacity is Apple’s ‘significantly degraded’ threshold and replacement is strongly recommended. Between 80-85 percent, replacement is optional. Above 85 percent, the battery is generally still fine.
What is a good iPhone battery health percentage?
New iPhones start at 100 percent. After a year of use, 90-95 percent is normal. After two years, 85-90 percent is typical. Anything above 80 percent is considered a healthy battery.
Does battery health below 80 slow down my iPhone?
Yes. iOS applies ‘performance management’ (CPU throttling) to prevent unexpected shutdowns on degraded batteries. You will see a warning on the Battery Health screen when this is active. Replacing the battery removes the throttling.
How do I find battery cycle count on iPhone?
iPhone 15 and later show Cycle Count in Settings > General > About > scroll down to Battery section. Older iPhones do not show cycle count directly — you would need a third-party tool like coconutBattery on Mac to read it from the hardware.
