iPhone battery health below 80 percent is considered degraded, and below 50 percent means the battery is failing

Apple defines battery health as the maximum charge your battery can hold compared to when it was new. You check it in Settings > Battery > Battery Health & Charging. A new iPhone shows 100 percent. Once it drops below 80 percent, Apple considers the battery degraded — it will not hold a full charge the way it did on day one. Below 50 percent, the battery is failing and your phone may shut down unexpectedly even when the percentage display shows charge remaining.

The number itself is not a prediction of when your battery will die. It is a snapshot of current capacity. An iPhone at 79 percent battery health will still work, but it will not last as long between charges as it did when new. At 50 percent, you are looking at a phone that may power off suddenly, restart on its own, or refuse to run demanding apps even though the battery indicator says 30 or 40 percent charge.

Battery health degrades naturally over time and use. Every charge cycle — from full to empty and back to full — wears the battery slightly. After roughly 500 full charge cycles, most iPhone batteries reach 80 percent health. After 1,000 cycles, they typically sit around 50 percent or lower. The speed depends on how you charge, how hot the phone gets, and how deeply you drain it each day.

Key Takeaways

  • Battery health below 80 percent means your iPhone will not hold a full charge the way it did when new, but the phone still works normally.
  • Battery health below 50 percent signals a failing battery that may shut down unexpectedly or refuse to run apps, even with charge showing on screen.
  • You can see your battery health percentage in Settings > Battery > Battery Health & Charging on any iPhone running iOS 11.3 or later.
  • Degradation is normal and happens faster if you regularly drain the battery completely, charge in hot conditions, or leave the phone plugged in overnight constantly.
  • Apple will replace the battery for a flat fee if health drops below 80 percent within the warranty period, or you can pay out of pocket at any time.

How battery health percentage translates to real phone performance

At 90 to 100 percent health, your phone behaves as designed. You get the full advertised battery life — roughly a full day of mixed use for most iPhones. Charging is fast and the battery accepts a full charge without issue.

At 80 to 89 percent health, you will notice the first real change. Your phone will not last quite as long between charges. If your iPhone normally made it through a full day, it might now need charging by evening. The difference is small enough that many people do not notice it right away, but it is measurable.

At 70 to 79 percent health, the drop becomes obvious. A phone that lasted 12 hours might now last 8 to 10. You will find yourself charging more often, and fast charging may take slightly longer because the battery is less efficient at accepting current.

At 50 to 69 percent health, the battery is noticeably weak. Your phone may last only 4 to 6 hours of active use. More importantly, iOS may set up performance management — the system throttles your processor to prevent sudden shutdowns. Apps open slower, games lag, and the phone feels sluggish even though the battery percentage says you have charge left.

Below 50 percent health, the battery is failing. Your phone may shut down at 20 or 30 percent battery, or even at 50 percent on a cold day. It may restart unexpectedly. Some apps will refuse to run. At this point, a replacement is not optional — the phone is unreliable.

Why battery health degrades faster in some situations

Heat is the single biggest factor. Lithium-ion batteries — the type in every iPhone — degrade much faster when warm. If you regularly charge your phone in a hot car, use it while charging, or leave it in direct sunlight, the battery will age faster than normal. Even leaving your phone plugged in overnight in a warm room accelerates degradation.

Deep discharge cycles also matter. If you regularly drain your battery all the way to zero and then charge it back to 100, you are putting more stress on the battery than someone who keeps it between 20 and 80 percent. This is why Apple recommends not letting your iPhone die completely and not leaving it plugged in at 100 percent for extended periods.

Fast charging and wireless charging are gentler than they used to be, but they still generate heat. If you fast-charge every day in a warm environment, your battery will degrade faster than someone who uses a standard charger in a cool room.

Age itself matters too. Even if you barely use your phone, the battery will degrade over time. A two-year-old iPhone sitting in a drawer will have lower battery health than a one-year-old iPhone used daily, though the difference is small.

What to do if your battery health is below 80 percent

If your iPhone is still under warranty — typically one year from purchase — and battery health has dropped below 80 percent, Apple will replace the battery at no cost. You can check your purchase date in Settings > General > About. If you are within the warranty window, contact Apple Support or visit an Apple Store to request a battery replacement.

If you are outside the warranty period, Apple charges a flat fee for battery replacement. The cost varies by iPhone model but typically ranges from $50 to $70. You can pay this at an Apple Store, through Apple's mail-in repair service, or at an authorized Apple service provider. The replacement takes one to three business days at most locations.

If you do not want to replace the battery yet, you can extend the phone's usable life by enabling Low Power Mode in Settings > Battery. This reduces performance but makes the battery last longer between charges. You can also reduce screen brightness, close unused apps, and turn off background app refresh to stretch battery life further.

If battery health is below 50 percent and you use your phone heavily, replacement is worth considering sooner rather than later. A failing battery makes the phone unreliable — unexpected shutdowns and performance throttling will get worse as health drops further.

How to check battery health on your iPhone

Open Settings on your iPhone. Tap Battery, then tap Battery Health & Charging. The screen shows your current battery health as a percentage and a statement about the battery's condition — either "Your battery is in good condition" or "Your battery's health is degraded."

This feature is available on iPhone 6s and later running iOS 11.3 or newer. If you have an older iPhone or older iOS version, you cannot see the exact percentage, though you can still request a battery health report from Apple Support.

The same screen also shows Peak Performance Capability. If your battery health is low enough that iOS is throttling performance, this section will tell you. It will say something like "This iPhone has experienced an unexpected shutdown because the battery was unable to deliver the necessary peak power." If you see this message, your battery needs replacement soon.

Battery health versus battery percentage — why they are different

Battery percentage is how much charge is currently in your battery — the number you see in the top right corner of your screen. Battery health is how much charge the battery can hold at maximum compared to when it was new. These are two separate things.

You can have 100 percent battery percentage but 60 percent battery health. This means your battery is fully charged right now, but that full charge is only 60 percent of what a new battery could hold. So if a new iPhone battery holds 3,000 milliamp-hours, yours holds only 1,800 — even when fully charged.

This is why an old iPhone with degraded battery health may show 100 percent on screen but still die quickly. The 100 percent is real — the battery is fully charged — but the maximum capacity is much lower than it was when new.

Frequently Asked Questions

Can I improve my battery health without replacing the battery?

No. Battery health reflects physical wear on the battery itself and cannot be reversed by software updates, settings changes, or charging habits. Once capacity is lost, only a hardware replacement restores it. You can slow future degradation by avoiding heat, not deep-discharging regularly, and not leaving the phone plugged in constantly, but past damage is permanent.

Is 85 percent battery health bad?

Not bad, but noticeably degraded. At 85 percent health, your iPhone will last noticeably shorter between charges than it did when new — typically 10 to 20 percent less runtime. If you use your phone lightly, you may not notice. If you rely on it all day without charging, you will feel the difference. Replacement is not urgent, but you should plan for it within the next year.

Will my iPhone slow down if battery health is low?

Yes, if health drops below roughly 50 percent. iOS activates performance management to prevent unexpected shutdowns, which throttles the processor. Apps open slower, games lag, and multitasking feels sluggish. This slowdown is intentional — it keeps the phone from dying suddenly — but it makes the phone feel old. Replacement fixes it when ready.

How long does an iPhone battery last before it needs replacement?

Most iPhone batteries reach 80 percent health after roughly 500 full charge cycles, which typically takes two to three years of normal use. After 1,000 cycles — usually four to five years — health is often around 50 percent or lower. The exact timeline depends on how you charge and use the phone. Heavy users may need replacement sooner; light users may go longer.

Does Apple replace the battery if I damaged my phone?

Apple will replace the battery if health is low, regardless of how the damage happened, as long as the battery itself is not physically damaged. If the battery is swollen, leaking, or visibly broken, Apple may refuse the replacement or charge an additional fee for damage. If the battery is straightforward worn out from normal use, replacement is straightforward.