Where to find battery health on your iPhone

Open Settings, then tap Battery, then Battery Health & Charging. You will see two numbers: Maximum Capacity and Peak Performance Capability. Maximum Capacity tells you what percentage of the battery's original charge it can still hold. Peak Performance Capability tells you whether the phone is running at full speed or if iOS has slowed the processor to protect an aging battery.

This screen is available on iPhone 6 and later. If you have an older model, you cannot see battery health through Settings. The Battery Health feature was added in iOS 11.3, released in March 2018.

Key Takeaways

  • Maximum Capacity shows what percentage of the original charge your battery can still hold; anything above 80 percent is considered normal wear.
  • Peak Performance Capability tells you whether iOS has slowed your phone's processor to prevent unexpected shutdowns on a weak battery.
  • A battery at 80 percent capacity still works, but will drain faster and may not last a full day of heavy use.
  • Apple offers battery replacement for a flat fee, usually between $50 and $70 depending on your model, which is cheaper than buying a new phone.

What Maximum Capacity percentage means

Maximum Capacity is measured as a percentage of what the battery could hold when the phone was new. A phone at 100 percent can hold a full charge. A phone at 80 percent can hold 80 percent of that original charge. If your original battery lasted 12 hours on a full charge, an 80 percent battery will last roughly 9.6 hours under the same conditions.

Apple considers 80 percent normal wear. Batteries degrade naturally over time and with use — this is not a defect. Most iPhones reach 80 percent capacity after 500 full charge cycles. A charge cycle means draining the battery completely and charging it back to 100 percent, though you do not have to do this in one day.

Below 80 percent, the battery still works, but you will notice the phone drains faster and may not last a full day if you use it heavily. Below 50 percent, the battery is significantly degraded and replacement is usually the practical choice.

Understanding Peak Performance Capability

Peak Performance Capability has three possible states: Normal, Reduced Performance, or Unknown. Normal means your phone is running at full speed. Reduced Performance means iOS has automatically slowed the processor to prevent the phone from shutting down unexpectedly when the battery cannot deliver enough power.

iOS applies this slowdown only when the battery is weak enough to cause problems. You will notice the phone feels slower — apps take longer to open, web pages load more slowly, and games may stutter. This is intentional: a slower phone is more useful than a phone that shuts itself off at 20 percent battery.

If you see Unknown, it means the phone cannot read the battery's health data. This can happen if the battery is very old, damaged, or not genuine. Restart the phone and check again. If it still shows Unknown, the battery may need replacement.

When to replace your iPhone battery

Replace the battery if Maximum Capacity is below 80 percent and you notice the phone drains noticeably faster than it used to, or if Peak Performance Capability shows Reduced Performance and you want full speed back. You do not have to replace it — a phone at 70 percent capacity still works — but you will get better daily use time and faster performance.

If Maximum Capacity is below 50 percent, replacement is usually worth the cost. At that point the battery drains so quickly that you may need to charge twice a day, and the phone may shut down unexpectedly even at 20 or 30 percent battery remaining.

Apple offers battery replacement at an Apple Store or through Apple's mail-in service. The cost is usually $50 to $70 depending on your iPhone model, plus tax. Third-party repair shops often charge less, but using a non-Apple battery may affect warranty coverage and performance. Check your phone's warranty status before paying for replacement — if the phone is less than one year old and the battery is below 80 percent, Apple may replace it for free.

How battery capacity degrades over time

Battery capacity drops fastest in the first year of use. Most iPhones lose 5 to 10 percent capacity in the first 12 months of normal use. After that, the decline slows. A phone used for three years might be at 70 to 75 percent capacity; a phone used for five years might be at 50 to 60 percent.

Heavy use speeds up degradation. Leaving the phone in hot environments, charging it constantly, or running demanding apps all day will lower capacity faster than light use. Keeping the phone between 20 and 80 percent charged most of the time, and avoiding heat, slows degradation slightly, but you cannot stop it entirely.

Checking battery health on older iPhones

If you have an iPhone 5s or earlier, the Battery Health & Charging screen does not exist. You can still get some information by opening Settings, tapping Battery, and looking at Battery Usage, which shows which apps have used the most power in the last 24 hours or last 10 days. This does not tell you the battery's actual health, but if the phone drains much faster than it used to, the battery is likely degraded.

For a precise reading on an older iPhone, you can visit an Apple Store and ask them to check the battery health. They can run a diagnostic that shows the exact capacity. This is free and takes a few minutes.

Frequently Asked Questions

Is 85 percent battery health good?

Yes. Apple considers 80 percent and above normal wear, so 85 percent is well within the expected range. You should not notice any significant slowdown or reduced battery life at this capacity. Most phones reach this point after one to two years of regular use.

Can I improve my battery health percentage?

No. Maximum Capacity only goes down; it cannot be restored by software updates, restarting, or changing settings. The percentage reflects actual chemical wear inside the battery. Only physical replacement raises the number back to 100 percent.

What does "Unknown" battery health mean?

It means the phone cannot read the battery's data, usually because the battery is very old, damaged, or not genuine. Restart the phone and check again. If it still shows Unknown after a restart, the battery likely needs replacement or the phone may have a hardware problem.

Does fast charging damage the battery?

Fast charging causes slightly more wear than slow charging, but the difference is small. iPhones are designed to handle fast charging safely. If you want to minimize battery wear, charge slowly and avoid letting the phone get too hot while charging, but normal fast charging will not significantly shorten the battery's life.

Should I replace my battery at 80 percent or wait until it is lower?

It depends on your use. If you use the phone heavily and need it to last all day, replace it at 80 percent. If you use it lightly or have access to a charger during the day, you can wait until 70 percent or lower. There is no wrong answer — it is a choice between cost now and convenience later.