What's actually wrong with your iPhone battery

An iPhone battery that won't hold a charge is almost always one of three things: the battery itself has worn out and lost capacity, something in iOS is draining it faster than normal, or a hardware problem is preventing the battery from charging fully. The first step is to figure out which one you have, because the fix is different for each.

Apple's batteries degrade over time. A new iPhone battery holds 100% of its designed capacity. After about 500 full charge cycles—roughly two years of normal use—a battery typically drops to 80% capacity. At 80% capacity, your phone still works, but it runs out of power faster. At around 50% capacity, iOS may start shutting down the phone unexpectedly to protect the battery. This is normal wear, not a defect, and the fix is a new battery.

If your phone is less than two years old and the battery drains quickly only sometimes, the problem is usually a rogue app or a setting that's been turned on. If the battery won't charge at all, or charges only when the phone is off, the issue is likely the charging port, the charging cable, or the battery itself.

Key Takeaways

  • Check your battery health in Settings > Battery > Battery Health & Charging to see if the battery has worn out; anything below 80% capacity means the battery needs replacement.
  • Force restart your iPhone by pressing and releasing Volume Up, pressing and releasing Volume Down, then holding the side button until the power-off slider appears, to clear software glitches that drain the battery.
  • Turn off Background App Refresh in Settings > General > Background App Refresh to stop apps from running when you're not using them.
  • If the phone won't charge, try a different USB-C or Lightning cable first, then try a different power adapter, because the cable or adapter fails more often than the charging port.
  • If the battery is below 80% capacity and you've ruled out software problems, the battery needs to be replaced by Apple or an authorized repair shop.

Check your battery health in Settings

Open Settings, tap Battery, then tap Battery Health & Charging. You'll see a number labeled "Maximum Capacity"—this is what percentage of the battery's original capacity remains. If it says 80% or higher, the battery itself is probably fine. If it says below 80%, the battery has worn out and needs replacement.

Below the capacity number, you may see a message about "Peak Performance Capability." If it says your phone has experienced unexpected shutdowns and iOS has reduced performance to protect the battery, your phone is throttling itself. This is a sign the battery is failing and should be replaced soon.

Write down the percentage. You'll need it if you decide to have the battery replaced, because some repair shops will ask for proof of the capacity before they start work.

Rule out software problems before replacing the battery

If your battery health is above 80% but the phone still drains quickly, a software issue is probably the cause. Start by force restarting the phone. Press and release the Volume Up button, press and release the Volume Down button, then hold the side button (the power button) until you see the power-off slider. Drag the slider to turn off the phone, wait 10 seconds, then press the side button again to turn it back on.

After the restart, use the phone normally for a day and watch whether the battery drains faster than before. Many software glitches clear themselves after a restart.

If the drain continues, go to Settings > General > Background App Refresh and turn it off. This stops apps from running in the background when you're not using them. Some apps—especially social media and email apps—will refresh constantly if you let them, and this drains the battery even when the phone is in your pocket. You can turn Background App Refresh back on later if you want, or leave it off and manually refresh apps when you open them.

Check which apps are using the most battery

Go to Settings > Battery and scroll down to see which apps have used the most battery in the last 24 hours or the last 10 days. If one app is using far more than the others—say, 40% or more—that app may have a bug or may be set to do something power-hungry in the background.

If you see an app you don't use often but it's high on the list, delete it or turn off its background activity. Go to Settings > Apps (or Settings > General > iPhone Storage), find the app, tap it, and look for options to turn off background refresh or notifications. If the app is one you need, check whether it has an update available in the App Store—updates often fix battery drain problems.

If no single app stands out, the problem may be a setting. Check Settings > Display & Brightness and make sure the brightness is set to auto-adjust, not locked at maximum. Check Settings > Privacy > Location Services and turn off location access for apps that don't need it. Location services, especially "Always" location access, drain the battery quickly.

Fix charging problems if the phone won't charge

If your iPhone won't charge, or charges only when the phone is powered off, start with the cable and adapter. The Lightning or USB-C cable wears out faster than the phone itself. Try a different cable first—borrow one from a friend if you need to. If the phone charges with a different cable, the original cable is damaged and needs to be replaced.

If a different cable doesn't work, try a different power adapter. Adapters fail often, especially cheap third-party ones. If you have access to another iPhone charger, plug it in and see whether the phone charges. If it does, your adapter is the problem.

If the phone still won't charge with a different cable and adapter, the charging port may be blocked with lint or debris. Look into the port with a flashlight. If you see lint, use a wooden toothpick or a plastic dental pick to gently scrape it out. Do not use metal, because metal can short the port. If the port looks clean and the phone still won't charge, the port itself may be damaged, or the battery may be failing. This requires professional repair.

When to replace the battery yourself versus getting professional help

Apple will replace an iPhone battery for a flat fee that varies by model—typically between $50 and $100. You can make an appointment at an Apple Store or an Apple Authorized Service Provider. The repair usually takes a few hours to a day. If your phone is still under warranty or covered by AppleCare+, the battery replacement may be free if the battery is defective.

Third-party repair shops, including some Best Buy locations, also replace iPhone batteries and often charge less than Apple. The trade-off is that you lose any remaining warranty coverage on the phone, and the quality of the repair depends on the shop. If you choose a third-party shop, look for one that uses genuine Apple batteries or high-quality aftermarket batteries, not cheap knockoffs.

Do not attempt to replace the battery yourself unless you have experience with phone repair. iPhones are glued together, and opening one without the right tools can damage the screen, the logic board, or the battery itself. A damaged battery can catch fire. If you're not confident, pay for professional repair.

Extend your battery's life after repair

Once you have a new battery, you can slow down how fast it wears out. Keep the phone cool—avoid leaving it in direct sunlight or in a hot car. Turn on Optimized Battery Charging in Settings > Battery > Battery Health & Charging. This setting learns when you charge your phone and slows down charging to 80% until you need to use the phone, which reduces wear on the battery.

Avoid letting the battery drain all the way to zero regularly. Charging from 20% to 80% is easier on the battery than charging from 0% to 100%. If you use your phone heavily, consider charging it twice a day instead of once.

Frequently Asked Questions

Why does my iPhone shut down even though the battery says 20%?

The battery has probably worn out and can no longer deliver the power the phone needs, even though it still holds a charge. This is especially common in cold weather. Check your battery health in Settings. If it's below 80%, the battery needs replacement. If it's above 80%, try a force restart—sometimes the phone's power management gets confused and shuts down prematurely.

Is it bad to leave my iPhone plugged in overnight?

No. Modern iPhones have Optimized Battery Charging turned on by default, which stops charging at 80% until a few hours before you usually wake up. This reduces wear on the battery. If you turn off Optimized Battery Charging, leaving the phone plugged in overnight will wear the battery faster, but it won't damage it when ready—it just ages it more quickly.

Can I use a fast charger without damaging the battery?

Yes. iPhones are designed to work with fast chargers, and the phone manages the charging speed automatically. Fast charging does generate more heat, which wears the battery slightly faster than slow charging, but the difference is small. If you're concerned about battery life, use a slower charger, but a fast charger won't ruin the battery.

What's the difference between a genuine Apple battery and a third-party battery?

Genuine Apple batteries are made to Apple's specifications and usually last longer. High-quality third-party batteries from reputable makers work well and cost less. Cheap knockoff batteries may not hold a charge as long, may not fit properly, or may overheat. If you use a third-party battery, buy from a shop with good reviews, not from an unknown seller online.

Does closing apps in the background save battery?

Not much. Closing apps manually doesn't save battery because iOS already suspends apps when you're not using them. The only thing that saves battery is turning off Background App Refresh, which prevents apps from running in the background at all. Closing apps manually is unnecessary.