Why Is My Phone Battery Draining So Fast? Causes and Fixes for iPhone and Android

It’s 2 p.m. and your phone is already at 15%. Yesterday it lasted all day. What changed?

Fast battery drain is one of the most common phone complaints, and the frustrating part is that it can have several causes at once. The good news is that both iPhone and Android now include tools that show exactly where your power is going. This guide walks you through a quick diagnosis, the usual culprits and how to tell when the battery itself is the problem.

Start with a quick diagnosis

Before changing settings at random, find out what’s actually using power.

On iPhone: Open Settings, Battery. You’ll see a chart of battery level and activity over the last 24 hours and 10 days, plus a list of apps ranked by their share of battery use. Apple notes this list doesn’t count time while the phone was charging. Apple may also flag apps that use a lot of power in the background.

On Android: Open Settings, Battery, Battery usage and view by apps. On Samsung phones, look under Settings, Battery (or Battery and device care). Menu names vary by manufacturer and Android version.

Look for anything surprising. An app you barely opened that sits near the top is a strong clue.

Try an overnight test

Google suggests a simple test on Pixel phones that works on any phone: charge it, leave it unplugged and idle overnight, and check the level in the morning. Google says that if the battery drains less than 10% overnight, it’s working as expected. If it drains more than 10%, something is using power in the background and you should check battery usage.

The usual culprits

Here’s a checklist of the most common causes and what to try for each.

Rogue apps

A single misbehaving app can drain a battery in hours. Navigation, video streaming, games, social media and apps that constantly sync are common offenders. Update the app first, since developers often fix battery bugs. If it keeps draining, restrict its background activity or remove it.

On iPhone, go to Settings, General, Background App Refresh to turn it off for apps that don’t need it. On Android, tap an app in the battery usage list to restrict background use.

Screen brightness

The display is often the biggest single power draw. Turn on auto-brightness, shorten the screen timeout and turn off always-on display features if you don’t need them. On phones with OLED screens, dark mode can help.

Weak signal

When signal is poor, your phone boosts its radio power to stay connected. If your battery always dies faster at work or in a particular building, weak signal is a likely cause. Wi-Fi calling helps indoors, and Airplane mode stops the hunt entirely when you don’t need calls.

Heat

Heat is hard on lithium-ion batteries. Apple says iPhone works best in ambient temperatures of 62° to 72° F (16° to 22° C), and that exposure above 95° F (35° C) can permanently reduce battery capacity. Apple also recommends removing certain cases while charging if they trap heat. Don’t leave your phone on a car dashboard in summer.

Key takeaway: Find the cause before changing settings. Battery usage screens and battery health tell you whether you have an app problem, a settings problem or a worn-out battery.

Is it your battery’s health?

All rechargeable batteries lose capacity as they age, so a 3-year-old phone simply holds less charge than it did new.

Checking battery health on iPhone

Go to Settings, Battery, Battery Health (Battery Health & Charging on some versions). Maximum Capacity compares your battery to when it was new. Apple says batteries in iPhone 14 models and earlier are designed to retain 80% of their original capacity at 500 complete charge cycles under ideal conditions, and iPhone 15 models and later at 1,000 cycles.

The Peak Performance Capability section tells you if your iPhone has applied performance management after an unexpected shutdown. If health is significantly degraded, Apple says a battery replacement by Apple or an Apple Authorized Service Provider restores full performance and capacity.

Checking battery health on Android

It depends on your phone. Google says Pixel 8a and later models show Settings, Battery, Battery health, with a status of Normal or Reduced. Reduced means capacity is below 80%, and Google suggests considering a replacement. Earlier Pixel models from Pixel 6 onward offer Battery Diagnostics instead. Samsung and other manufacturers include their own battery and diagnostics tools, often in a device care or members app.

Settings that extend battery life

Once you’ve ruled out a rogue app, these settings help every phone:

1. Low Power Mode (iPhone) or Battery Saver (Android). Apple says Low Power Mode reduces display brightness and limits background activity, and the phone prompts you to turn it on at 20% and 10%.
2. Adaptive Battery (Android). Google says Adaptive Battery and battery optimization are on by default and help apps use power only when needed. Keep them on.
3. Location set to “While Using.” Few apps need your location all the time.
4. Fewer notifications. Every alert wakes the screen. Turn off notifications from apps you don’t need to hear from.
5. Keep software updated. Updates often include battery and performance fixes.

Charging habits that slow battery aging

• Optimized Battery Charging (iPhone): On by default, it pauses at 80% and finishes charging closer to when you usually unplug, after learning your routine for at least 14 days.
• Charge Limit (iPhone 15 and later): Apple lets you set a maximum charge between 80% and 100% in 5% steps under Settings, Battery, Charging.
• Android equivalents: Pixel phones offer adaptive charging and battery protection options, and Samsung includes battery protection settings. Check your phone’s battery settings for names on your model.

Where to start: a 10-minute fix plan

1. Restart your phone. It clears stuck processes.
2. Open battery settings and note the top 3 apps.
3. Update or restrict any app using more than its fair share.
4. Turn on auto-brightness and shorten the screen timeout.
5. Limit background refresh and set location access to “While Using.”
6. Check battery health. If it’s below about 80% or the phone shuts down unexpectedly, book a battery replacement.
7. Run the overnight test again after a day of normal use.

A very full phone can also run hotter and work harder during updates. If you’re low on space, see our guide to freeing up iPhone storage. And if you’re thinking about resetting your phone as a last resort, back up your phone first.

When to replace the battery or the phone

Replace the battery if health has dropped below about 80%, if your phone shuts down at 20% or 30%, or if the battery is visibly swollen. A swollen battery is a safety concern: stop using and charging the phone and get it to a repair provider. Battery replacement is usually far cheaper than a new phone, and Apple says its warranty covers a defective battery, with paid service available out of warranty. Prices vary by model and provider.

If the phone is old enough that it no longer gets security updates, a new phone may make more sense. When you upgrade, our guide on how to transfer data to a new phone covers everything you need to move. Many newer phones also run AI features on the device itself, which we explain in our guide to small language models and on-device AI.

Conclusion

Fast battery drain almost always has a findable cause. Check battery usage to catch rogue apps, adjust the screen and background settings, keep your phone cool and check battery health. If the battery has simply worn out, a replacement brings most phones back to all-day life. For any unfamiliar terms, see our glossary.

Sources

• Apple Support: iPhone battery and performance — Maximum Capacity, 500 and 1,000 cycle design targets, peak performance and service
• Apple: Maximizing battery life and lifespan — temperature range, Low Power Mode, cases while charging and background activity
• Apple Support: About Charge Limit and Optimized Battery Charging on iPhone — 80% pause, 14-day learning period and charge limit settings
• Pixel Phone Help: Understand your Pixel battery — Battery health status on Pixel 8a and later
• Pixel Phone Help: Fix battery drain problem — overnight drain test and battery usage checks
• Pixel Phone Help: Keep Adaptive Battery and battery optimization on — Adaptive Battery defaults