iPhone battery health explained: what the number means and when to replace

Go to Settings > Battery > Battery Health (Apple Support). You’ll see two things: a Maximum Capacity percentage and a Peak Performance Capability message. The second one matters more.

What “Maximum Capacity” means

It’s your battery’s capacity compared with when it was new. At 90%, a full charge holds about 90% of what it used to. You’ll notice it as fewer hours between charges, not as a slower phone.

How fast it should drop (Apple’s numbers)

Apple designs batteries to keep 80% of their original capacity at:

• 500 complete charge cycles for iPhone 14 and earlier;
• 1,000 complete charge cycles for iPhone 15 and later.

Those figures assume ideal conditions. Heat, fast charging in a hot car and spending days at 100% all speed up wear.

The messages, in plain English

• “Your battery is currently supporting normal peak performance.” All good, whatever the percentage.
• Performance management applied. Your iPhone had an unexpected shutdown because the battery couldn’t deliver peak power, so iOS is limiting performance to stop it happening again. A new battery removes this.
• “Battery health degraded.” Apple says the battery has degraded significantly and recommends a replacement by Apple or an Apple Authorized Service Provider. Apple notes it isn’t a safety issue.
• “Unable to verify this iPhone has a genuine Apple battery.” The battery was replaced with a part iOS can’t verify, so the health figures may not be accurate.

When to replace it

Replace the battery when either is true:

1. you see “Battery health degraded”, or performance management keeps applying after shutdowns; or
2. the phone no longer gets you through your normal day, whatever the percentage says.

Above 80% with normal peak performance? You probably don’t need one yet.

Where to replace it

Apple and Apple Authorized Service Providers use genuine parts, and Battery Health keeps working. Check Apple’s support site for the price for your model. If you use an independent shop, ask whether they use a genuine battery, and expect the “unable to verify” message if they don’t. We cover the repair debate in Samsung may lock Galaxy batteries to official parts.

Make the next battery last longer

• Use a charge limit or Optimized Charging. On iPhone 15 and later, Settings > Battery > Charging lets you set a limit.
• Keep the phone out of heat, especially while charging.
• More tips: How to make your phone battery last longer.

Our take

Watch the message, not the percentage. A phone at 82% with normal peak performance is fine; one that shuts down in the cold needs a battery, whatever the number says. A new battery is the cheapest way to make an older iPhone feel new again.

Prices checked on 2026-10-23.

Sources

• Official Apple Support: iPhone battery and performance (checked Oct 23, 2026)