Why Is Your Phone Battery Draining So Fast? Find the Cause, Then Fix It
It is 7 p.m., you have been out all day, and your phone is at 12 percent. It was fully charged this morning. Nothing about today was unusual — a few calls, some scrolling, one video — yet the battery has quietly emptied itself. Most people respond by changing a random setting or downloading a “battery saver” app. Both are guesses. The fix starts somewhere else: find out what is actually draining the battery, then fix that one thing.
This guide does exactly that, in order. First you find the culprit on the battery usage screen. Then you check whether the battery itself is worn out, because no setting fixes a dying battery. Then the fixes, for iPhone, Android and Samsung, followed by the myths that waste your time. The whole diagnosis takes about five minutes.
The short version: open your battery usage screen (iPhone: Settings > Battery; Android: Settings > Battery > Battery usage), see which app or feature used the most power, and deal with that one first. Then check battery health — around 80 percent of original capacity is the point to think about a replacement. Most fast drain is one misbehaving app, a worn battery, or the screen.
Step 1: Find the culprit on the battery usage screen
On an iPhone, go to Settings > Battery. The screen shows a chart of your usage and, below it, every app ranked by how much battery it used, split into screen time and background time. The background number is the important one. If an app you barely opened sits near the top — Instagram, TikTok, a navigation app, or even the Google app refreshing its Discover feed — you have your suspect.
On Android, go to Settings > Battery > Battery usage and switch to the view by apps. On a Pixel the same screen shows a chart since the last full charge. On a Samsung Galaxy, open the Samsung Members app and run Phone diagnostics > Battery status, or check Settings > Battery and device care. The rule is the same on every phone: one app using 30 percent or more while you barely touched it is not normal use. It is a bug, a bad update, or an app that never sleeps.
Found a culprit? Update the app first — the bug may already be fixed — then restrict its background activity, and uninstall it if the drain continues. Do not start by changing ten settings at once. If you change everything, you will never know which one worked, and you will have made your phone worse to use for nothing.
Step 2: Check battery health — is the battery itself worn out?
Every phone battery wears out. Each full charge cycle slightly reduces the maximum charge it can hold, and after enough cycles the same use that once lasted a full day ends by evening. Before you blame your apps, check whether the battery itself is the problem.
On an iPhone, go to Settings > Battery > Battery Health and look at Maximum Capacity — the percentage of its original capacity the battery can still hold. Apple designs iPhone 14 models and earlier to keep about 80 percent of original capacity after 500 complete charge cycles, and iPhone 15 models and later to keep 80 percent after 1,000 cycles. Apple and Google both treat around 80 percent as the point to think about a replacement. If the screen also says “Battery health significantly degraded,” that is Apple telling you the battery is the problem, not your settings.
On Android there is no single built-in health percentage on every phone. On a Pixel 6 or later, open Settings > Battery > Battery diagnostics and run the battery check. On a Samsung Galaxy, the Samsung Members diagnostics give a Battery status result: Normal means no issue, Weak means efficiency may have decreased, and Bad means battery life is significantly degraded — Samsung advises contacting a support centre for a Bad result. As a rough guide, a phone two to three years old that needs charging twice a day has very likely crossed the line, whatever the menus say.
If the battery is worn out, no setting will bring it back. A replacement battery — fitted by Apple, Samsung, Google or an authorised repairer — usually costs far less than a new phone and restores the phone to a full day. That is the right fix when health is low, and the wrong fix when it is not, which is why this check comes before the settings.
The seven most common causes, in order of likelihood
1. A worn battery. Covered above. Two to three years of daily charging puts most batteries near the 80 percent line.
2. The screen. The display is usually the single biggest power drain. High brightness, a long screen timeout and always-on display all add up. Auto-brightness and a 30-second timeout are the two cheapest fixes on any phone.
3. A misbehaving app. An app that keeps refreshing, syncing or tracking location in the background can empty the battery while the phone sits in your pocket. Social media, navigation and shopping apps are the usual suspects.
4. Poor signal. In a weak-coverage area the phone keeps searching for a better signal, which drains the battery. Apple’s battery screen even labels this: “No Mobile Coverage and Low Signal.” A basement, a rural road or a crowded building can do it.
5. 5G in weak coverage. 5G is efficient where the signal is strong, but constantly searching for a patchy 5G signal drains power. Both Apple and Google ship settings that fall back to LTE when 5G adds nothing.
6. Heat. Google warns that heat drains the battery faster even when the phone is idle, and Apple says ambient temperatures above 35°C (95°F) can permanently reduce battery capacity. Gaming, charging under a pillow or leaving the phone in a hot car all count.
7. A recent update. Right after a big system update, background work causes extra drain while the phone re-indexes and optimises. Google says this is normal for a few days, and Apple advises waiting a few days before judging the battery. If the drain started the day after an update and nothing else changed, wait before you change anything.
iPhone fixes
Turn on Low Power Mode when you need the day to last. Settings > Battery > Low Power Mode cuts background activity, visual effects and mail fetch. Your iPhone prompts you to enable it at 20 percent and again at 10 percent.
Limit Background App Refresh. Go to Settings > General > Background App Refresh and turn it off for social media, news and shopping apps — check them manually instead. Leave it on for messaging and mail if you need notifications on time.
Audit location access. Settings > Privacy & Security > Location Services. Apps set to “Always” keep GPS working in the background. Change them to “While Using” unless the app genuinely needs to know where you are all day.
Tame the screen. Turn on auto-brightness (Settings > Accessibility > Display & Text Size), set the screen to lock after 30 seconds, and switch off always-on display if you do not need it.
Turn on Optimised Battery Charging. It learns your daily routine and slows charging past 80 percent, reducing the time the battery spends fully charged, which slows aging. Apple also advises keeping the phone between 16°C and 22°C where possible, and never charging it above 35°C.
Keep iOS updated. Apple ships battery fixes in updates, and an outdated system can miss them. Check Settings > General > Software Update.
Android and Samsung fixes
Leave Adaptive Battery on. On a Pixel, it is at Settings > Battery > Battery Saver > Adaptive Battery. Google says it learns how you use the phone and lets apps you rarely open run less while idle. Learning can take a few weeks after setup or a factory reset, so do not judge it on day one.
Keep per-app battery use at Optimized. On a Pixel, go to Settings > Apps > See all apps, tap the app, then App battery usage, and leave background usage at Optimized. Only restrict a specific app when Battery usage has already shown it is the drain — restricting everything makes notifications and sync unreliable.
Use Battery Saver when the day matters more than background work. It limits background activity, and some visual effects, features and network connections may be delayed. Turn it on when you need the phone to last until you can recharge, not as a permanent setting.
Clear the cache of the heaviest apps. Apps such as Chrome, Instagram, TikTok and Spotify keep caches of thumbnails and video that can grow to several gigabytes. Go to Settings > Apps, tap the app, then Storage, then Clear cache. Clearing the cache is safe — the app rebuilds it and you stay logged in. Do not tap Clear data by mistake: that wipes logins and offline content.
On Samsung, use Device care. Settings > Battery and device care > Battery shows the same usage breakdown and offers optimisation, and the Samsung Members diagnostics check the battery itself.
Myths that do not help
Force-closing apps does not save battery. This is the most repeated battery myth on both platforms. When you swipe an app away, the phone has to load it from scratch next time, which uses more power than leaving it paused in memory. Apple and Google both design their systems to freeze unused apps. Only force-close an app that is actually misbehaving — frozen, or visibly draining power in the usage screen.
Turning off Bluetooth and Wi-Fi barely matters. Modern Bluetooth and Wi-Fi draw minimal power when not connected to anything. Turning them off saves almost nothing and costs you your headphones, watch and automatic connections. Poor mobile signal is the real radio drain, not Bluetooth.
“Battery saver” cleaner apps do not help. The Play Store and App Store are full of apps that promise to extend battery life. Most do nothing, some show aggressive ads, and a few are outright scams. Your phone already has every tool in this guide built in.
There is no secret calibration trick. Draining the battery to zero and charging to 100 percent does not “recalibrate” a modern lithium-ion battery. It just adds a full cycle of wear. Charge when it suits you; the phone manages the rest.
Charging habits that slow the wear
Batteries age fastest at the extremes: kept at 100 percent for days, regularly run to zero, or charged while hot. The habits that slow aging are unglamorous. Use Optimised Battery Charging on iPhone or Adaptive Charging on Android, which hold the charge at 80 percent overnight and finish just before you wake. Do not leave the phone charging on a hot dashboard or under a pillow. And use a decent charger — not because a cheap one drains the battery faster, but because heat and poor voltage regulation age it faster. None of this will rescue a battery already at 75 percent health. It is about making the next battery last longer than the last one.
When to replace the battery — and when to replace the phone
Replace the battery when health is around 80 percent or lower, when the phone says “significantly degraded” (iPhone) or “Bad” (Samsung diagnostics), or when the phone needs charging twice a day despite the fixes above. A battery replacement is usually the cheapest way to get another two years out of a phone you otherwise like.
Replace the phone when the battery is only one problem among many: the phone no longer gets security updates, apps are dropping support, or the cost of the battery plus other repairs approaches the value of the device. A new battery in a phone that cannot run current software is money spent on the wrong thing.
How to stop it happening again
Check the battery usage screen once a month — two minutes, and it catches a rogue app before it costs you a week of bad battery life. Keep your apps and system updated, because battery-draining bugs get fixed quietly in updates. Leave Adaptive Battery (Android) or Background App Refresh limits (iPhone) switched on instead of turning everything back up after one fix. And remember the heat rule: the single most damaging thing most people do to a battery is not a setting at all, it is leaving the phone in a hot car.
Frequently asked questions
Does force-closing apps save battery? No. Frozen apps in memory use almost no power, and reopening them from scratch costs more. Only force-close an app that is frozen or draining power.
Will a new battery fix my old phone? If battery health is the problem — around 80 percent or lower, or a “significantly degraded” message — yes, a replacement usually restores a full day. If health is fine, the drain is software, and a new battery will not help.
Why is my battery worse right after an update? After a major update the phone does background work for a few days — re-indexing, optimising apps, relearning usage. Google says this is normal. Judge the battery a week after the update, not the day after.
Sources: Apple’s guidance on iPhone battery and performance and on charging and maintaining the battery, and Google’s guide to saving battery on Android, were used to verify the settings, cycle counts and health thresholds in this guide. Apple Support: iPhone battery and performance · Apple: Maximizing battery life and lifespan · Android: How to save battery life and stop it from draining
Related: if your phone is also running out of room, see our guide to phone storage full — how to free up space on iPhone and Android.
