Replace your iPhone battery when it no longer holds a full day of normal use, when the phone shuts down unexpectedly at 20–30% charge, or when the battery health drops below 80%.

Your iPhone's battery degrades over time because lithium-ion batteries lose capacity with every charge cycle. A charge cycle means using 100% of your battery's capacity—not necessarily in one day. After 500 full cycles, Apple's batteries typically retain about 80% of their original capacity. You do not have to wait until your phone is completely dead to replace the battery; the right time depends on how the battery behaves in daily use.

The most practical sign is when your phone no longer lasts through a normal day without charging. If you are plugging in by mid-afternoon when you used to make it to evening, your battery is aging. The second sign is unexpected shutdowns: if your iPhone powers off at 20%, 30%, or even 50% charge, the battery cannot deliver the power your phone needs, even though it shows charge remaining. These shutdowns happen because the battery's internal resistance has increased.

Key Takeaways

  • Check your battery health in Settings > Battery > Battery Health & Charging; anything below 80% means the battery is aging faster than normal.
  • Unexpected shutdowns at mid-range charge levels (20–50%) are a sign to replace the battery soon, because the battery cannot supply the power your phone demands.
  • If your phone lasts a full day of normal use, you can wait to replace the battery even if health is below 80%—there is no urgent important date.
  • Battery replacement at an Apple Store or authorized repair shop costs between $50 and $100 depending on your iPhone model, and takes one to two hours.
  • Keeping your phone between 20% and 80% charge and avoiding extreme heat slows battery aging, but does not stop it.

How to Check Your Battery Health Right Now

Open Settings, tap Battery, then tap Battery Health & Charging. You will see a percentage labeled "Maximum Capacity"—this is how much charge your battery holds compared to when it was new. A new iPhone shows 100%. At 80%, your battery is still functional but noticeably aged. At 50% or lower, you should plan to replace it soon.

Below Maximum Capacity, you may also see "Battery Health Management" toggled on. Apple turns this on automatically to slow aging by limiting how high your battery charges. If this is on and your Maximum Capacity is still dropping, the battery itself is degrading faster than normal, which usually means replacement is due within weeks or months.

Signs Your Battery Needs Replacement Soon

The clearest sign is unexpected shutdown. If your iPhone powers off when the battery indicator shows 20%, 30%, or even 50%, the battery cannot deliver the current your processor and screen demand at that moment. This happens because the battery's internal resistance has climbed too high. The phone is not broken—the battery straightforward cannot keep up. Restarting the phone will turn it back on, and the percentage will jump back up, but this cycle repeats and gets worse.

A second sign is rapid drain during normal tasks. If your battery drops 10–15% per hour during light use (texting, email, web browsing), and this is new behavior, the battery is aging. Compare this to a few months ago: did you used to get 10 hours of light use per charge, and now you get 6? That is battery aging, not a software problem.

The third sign is slow charging or charging that stops partway. If your phone charges to 80% and then crawls to 100% over an hour, or if it stops charging entirely and you have to unplug and replug the cable, the battery is likely failing. This is different from a slow charger—it is the battery refusing to accept charge.

When You Can Wait Longer

If your battery health is 70–80% but your phone still lasts a full day of normal use, you do not have to replace it when ready. Many people use iPhones with 60–70% health for months without problems, as long as they do not mind charging more often. The decision is yours: if you are home most of the day or near a charger, waiting is fine. If you travel or work away from outlets, replacing the battery sooner makes sense.

You should not wait if you see unexpected shutdowns, because they will become more frequent and more disruptive. You also should not wait if your phone is more than four years old and you plan to keep it for another two years—the battery will likely fail completely before then, and replacement now is cheaper than an emergency repair later.

Where to Replace Your iPhone Battery

Apple Stores offer battery replacement for most iPhone models. The cost ranges from $50 to $100 depending on your model (older iPhones cost less, newer ones more). The repair usually takes one to two hours if you walk in without an appointment, or you can book online and come back at a set time. Apple will run diagnostics first to confirm the battery is the problem.

Authorized Apple repair shops—usually phone carriers like Verizon or AT&T, or independent repair shops certified by Apple—offer the same service at the same price. If you have AppleCare+, battery replacement is covered at no cost as long as the battery health has dropped below 80% due to normal use (not physical damage).

Third-party repair shops often charge $30–60 for battery replacement, but quality varies widely. If you choose a non-Apple shop, check reviews and ask whether they use genuine Apple batteries or aftermarket ones. Aftermarket batteries may not last as long or charge as reliably.

How to Slow Battery Aging Before Replacement

Keep your phone between 20% and 80% charge as much as possible. Charging from 0% to 100% every day stresses the battery more than charging from 30% to 80%. You can turn on Optimized Battery Charging in Settings > Battery > Battery Health & Charging, which limits charging to 80% overnight and finishes the last 20% an hour before you usually wake up. This small change noticeably slows aging over months.

Avoid heat. Do not leave your iPhone in a hot car, in direct sun for long periods, or in a case while charging if the phone gets warm. Heat degrades lithium-ion batteries faster than anything else. If your phone feels warm to the touch during normal use, remove the case and let it cool.

These steps slow aging but do not stop it. Your battery will still lose capacity over time—that is the nature of lithium-ion chemistry. The goal is to extend the time before replacement becomes necessary.

Frequently Asked Questions

Does a software update fix battery drain?

Software updates sometimes improve battery life by fixing bugs that cause apps to run constantly in the background. However, if your battery health is below 70% and you see unexpected shutdowns, a software update will not fix the battery itself. Install the update anyway—it may help—but plan to replace the battery if the problem continues.

Can I replace the battery myself?

You can buy a replacement battery and tools online, but opening an iPhone requires removing the screen, which is difficult without the right equipment. If you crack the screen during the process, repair costs $200–400. Unless you have done this before, having a professional do it is safer and often cheaper when you factor in the risk of damage.

What happens if I ignore a failing battery?

The phone will shut down more often and at higher charge levels. Eventually, it may shut down so frequently that the phone becomes unusable, even though it still powers on. At that point, you must replace the battery to use the phone. There is no risk of the phone catching fire or exploding—modern iPhones have multiple safety systems—but the phone will become unreliable.

Is battery replacement worth it, or should I buy a new phone?

If your iPhone is two to four years old and works well otherwise, battery replacement for $50–100 is much cheaper than a new phone. If your iPhone is five years or older, consider whether you want to keep it for another two years; if yes, replace the battery now. If you are ready to upgrade anyway, a new phone makes more sense than a battery replacement.

Will replacing the battery erase my data?

No. Battery replacement does not touch your storage or data. Your photos, messages, and apps stay exactly as they are. The technician removes the battery and installs a new one; nothing else changes on the phone.