Why you might need to drain your iPhone battery completely

You drain an iPhone battery to the point of shutdown when you want to recalibrate it — that is, reset the battery meter so iOS reads the actual charge level correctly. If your phone shuts down at 20 percent, claims it is dead at 40 percent, or won't hold a charge for as long as it used to, a full drain and recharge cycle can fix the mismatch between what the battery actually holds and what the software thinks it holds.

A complete drain also helps when you are troubleshooting power problems, preparing a phone for storage, or wiping a device before you sell or give it away. In each case, you want the battery to reach zero percent and the phone to power off on its own.

Key Takeaways

  • Draining your iPhone battery fully recalibrates the battery meter and can fix inaccurate charge readings.
  • The fastest way to drain the battery is to use power-heavy features like video playback, GPS navigation, or gaming at full brightness.
  • Disabling Low Power Mode and turning off Wi-Fi and Bluetooth forces the phone to work harder and drain faster.
  • Once the phone shuts down, plug it in and charge it to 100 percent without interruption to complete the recalibration.

Disable Low Power Mode and background activity

Before you start draining, turn off Low Power Mode if it is on. Go to Settings > Battery or Settings > Battery and Device Management, find Battery Health & Charging, and toggle Low Power Mode off. This removes the software limit that slows down the processor and extends battery life.

Next, disable Wi-Fi and Bluetooth. Swipe down from the top right corner to open Control Center, tap the Wi-Fi icon to turn it off, and tap the Bluetooth icon to turn it off. With these radios off, your phone cannot connect to networks or accessories, so it cannot enter low-power states and will drain faster.

Go to Settings > General > Background App Refresh and turn it off. This stops apps from updating in the background when the screen is off, which would otherwise slow the drain.

Use power-heavy features at maximum brightness

The screen is the biggest power consumer on an iPhone. Set brightness to 100 percent: go to Settings > Display & Brightness and drag the brightness slider all the way to the right. Turn off Auto-Brightness so the screen stays at full brightness even in dim light.

Open a power-heavy app and leave it running. Video playback is the most reliable choice — open the Videos app or YouTube and play a video on repeat. Gaming works well too; apps like Asphalt or Fortnite will drain the battery faster than video because they also use the processor heavily. Maps with GPS navigation running is another option.

Leave the app running with the screen on until the battery drains completely. The phone will warn you at 20 percent and 10 percent; ignore these warnings and keep the app open. When the battery reaches zero, the phone will shut down on its own.

Speed up the drain with multiple features at once

If you want to drain the battery faster, combine power-heavy features. Open Maps, enable GPS navigation to a destination far away, and let it navigate while a video plays in a smaller window using Picture in Picture. This forces the processor, GPS radio, screen, and speaker to all work at once.

Alternatively, open a video call app like FaceTime or WhatsApp and make a call to a contact or group. Video calls use the camera, microphone, screen, and cellular or Wi-Fi radio simultaneously, draining the battery quickly even though you disabled Wi-Fi earlier — you can re-enable it just for the call if needed.

Keep the screen on and the app active until the phone powers off. Do not lock the screen or put the phone to sleep, because that will slow the drain significantly.

What to do after the battery reaches zero

Once your iPhone shuts down, wait a few minutes before plugging it in. This ensures the battery is truly at zero and the phone has fully powered off.

Plug the phone into a charger — use the original Apple charger or a certified third-party charger for best results — and let it charge to 100 percent without interruption. Do not use the phone, open apps, or take calls while it charges. This uninterrupted charge cycle recalibrates the battery meter and restores accurate readings.

Charging from zero to 100 percent usually takes 1 to 2 hours depending on the charger and the iPhone model. Once it reaches 100 percent, unplug it and use the phone normally. The battery meter should now read accurately.

When a full drain does not fix the problem

If you drain and recharge the battery completely and the phone still shuts down early or reads the charge incorrectly, the battery itself may be degraded. Check the battery health by going to Settings > Battery or Settings > Battery and Device Management > Battery Health & Charging and looking at the Maximum Capacity percentage.

If Maximum Capacity is below 80 percent, the battery has degraded and a full drain will not restore it. At that point, you have two options: replace the battery through Apple or an authorized repair shop, or continue using the phone and accept the reduced battery life. Apple offers battery replacement for a fee; the cost varies by iPhone model but typically ranges from $50 to $100.

Frequently Asked Questions

Will draining the battery damage my iPhone?

No. Draining the battery to zero and recharging it once will not damage the phone or the battery. Modern iPhones are designed to handle full discharge cycles. However, repeatedly draining the battery to zero every day will degrade the battery faster than normal use, so do this only when you need to recalibrate.

How long does it take to drain an iPhone battery completely?

It depends on the model and what you are doing. Using video playback or gaming at full brightness typically drains the battery in 4 to 8 hours. Older models drain faster; newer models with larger batteries take longer. Using multiple power-heavy features at once can cut the time in half.

Can I drain the battery while the phone is plugged in?

No. If the phone is plugged into a charger, the charger will supply power faster than the battery drains, and the battery level will stay the same or increase. Unplug the phone completely before you start draining it.

What if my iPhone won't turn on after it drains completely?

This is normal. When the battery reaches zero, the phone shuts down and will not respond to button presses or taps. Plug it into a charger and wait 30 seconds to a minute; the Apple logo should appear and the phone will begin charging. It may take a few minutes of charging before the phone has enough power to turn on.