iPhone battery draining after iOS 27? How to fix it
iPhone battery draining fast since iOS 27? Why it happens after an update and how long to wait, how to find the app using it, Background App Refresh, Location, the screen, Adaptive Power and Low Power Mode, and when it’s the battery itself. UK and US, with a fix finder.
HanaHow6 minute readIf your iPhone’s battery has run down faster since you updated to iOS 27, it’s usually one of three things: the update still finishing in the background, an app working while you’re not using it, or a battery that’s worn. The fixes below go in that order, and the fix finder takes you through them one at a time. Settings paths are iOS 27’s. Where the UK and US labels differ, the US one is in brackets.
What’s happening?
Pick the closest. Each step says where to find it in Settings on iOS 27.
Give it a few days
After a big update, your iPhone carries on with update tasks in the background. That uses battery and can make it feel warm, which Apple says is normal. When the work finishes, battery life goes back to normal.
- Open Settings and tap Battery. Just above Daily Usage you may see an Insight called Ongoing iOS Update, or Ongoing Device Setup. That means it’s still working.
- Use your iPhone as normal for a few days, then check again.
- If a temperature warning appears, turn it off and let it cool somewhere out of the sun.
A few days on, is the battery back to normal?
See this in the guideInstall the latest update
- Go to Settings, General, Software Update.
- If there’s a newer iOS 27 release, install it. Apple’s own battery advice starts with this.
- Give it a day of normal use afterwards.
Updated and given it a day. Any better?
See this in the guideFind what’s using your battery
- Go to Settings, Battery, and scroll down to App and System Activity. It lists what used your charge today.
- For earlier days, tap View All Battery Usage, then a day.
- Tap an app to see why. A lot of Background time means it’s busy while you’re not using it. A Cellular Coverage note means it ran on a weak signal, which uses more battery.
Does one app stand out?
See this in the guideStop the app working in the background
- Background App Refresh: go to Settings, General, Background App Refresh, and switch it off for that app. The top row there switches it off for every app, or limits it to Wi-Fi.
- Location: go to Settings, Privacy & Security, Location Services, tap the app and choose While Using the App, or Never. Leave Location Services itself on: Apple says many features stop working without it.
- Notifications: if it wakes your phone a lot, go to Settings, Notifications, tap the app and turn off what you don’t need.
- Still heavy? Apple’s advice is simply to use that app less.
Give it a day. Has the app dropped down the list?
See this in the guideUse Wi-Fi when you can
Most of the time, Wi-Fi uses less battery than mobile data, and a weak signal makes your iPhone work harder to stay connected.
- At home and at work, join the Wi-Fi in Settings, Wi-Fi.
- On iPhone 12 and later, check 5G is on Auto: Settings, Mobile Service (Cellular), then Mobile Data Options (Cellular Data Options), Voice & Data, 5G Auto.
- Somewhere with no signal for hours? Airplane Mode stops it searching.
Lasting longer?
See this in the guideDim the screen, keep Auto-Brightness on
- Drag the brightness slider down in Control Centre (Control Center). Dimming the screen helps.
- Leave Auto-Brightness on: Apple says turning it off can use more power. It’s in Settings, Accessibility, Display & Text Size.
- Check Settings, Display & Brightness, Auto-Lock isn’t set to Never.
Any better?
See this in the guideUse Power Mode
- iPhone 15 Pro and later: go to Settings, Battery, Power Mode, and check Adaptive Power is on. It starts off on iPhone 15 Pro, 15 Pro Max and iPhone 16 models, and needs at least a week to learn your habits. On heavy days it dims the screen a little, lets some activity take longer, and at 20% it can turn on Low Power Mode.
- Low Power Mode, any iPhone: Settings, Battery, Power Mode, Low Power Mode on iPhone 15 and later, or Settings, Battery, Low Power Mode on iPhone 14 and earlier. It switches itself off once you’ve charged to 80%.
Does it get you through the day now?
See this in the guideCheck Battery Health
If none of that helps, it may be the battery itself.
- Go to Settings, Battery, then Battery Health on iPhone 15 and later, or Battery Health & Charging on iPhone 14 and earlier.
- Look at Maximum Capacity: how much charge it holds compared with when it was new.
- iPhone batteries are designed to keep 80% after 500 full charge cycles in ideal conditions, or 1,000 on iPhone 15 and later.
Is it below 80%, or does it say Service, or that its health is significantly degraded?
See this in the guideA new battery should help
- AppleCare? Apple replaces the battery at no extra charge if it’s below 80%.
- Under a year old? The warranty covers a faulty battery, on top of your consumer rights.
- Otherwise, Apple’s battery replacement page gives an estimate for your model: UK, US.
- Use Apple or an Authorised Service Provider, so it’s a genuine battery.
Healthy battery, still draining
- Contact Apple Support through support.apple.com/contact, or book an Apple Store or Authorised Service Provider, and say what you’ve tried. The list above helps.
- Adaptive Power just switched on? It needs at least a week to learn your habits, so give it that long.
Lasting again. Keep it that way.
- Keep iOS up to date: Settings, General, Software Update.
- Don’t bother swiping apps away. Apple says your iPhone manages background apps itself, so closing them doesn’t save battery.
- Leave Auto-Brightness on, and check Battery now and then for anything new at the top of the list.
Give it a few days after updating
After a big update, your iPhone carries on with update tasks in the background. Apple says these can affect battery life and make it feel warmer for a while, and that this is normal. When the work finishes, battery life goes back to normal. Apple’s advice is to wait a few days, then check again.
You can see it happening. Open Settings and tap Battery. Just above Daily Usage, an Insight may say Ongoing iOS Update (“A recent software update is finishing in the background”) or Ongoing Device Setup (“Your device is completing setup steps in the background”). Either means it hasn’t finished yet.
If a temperature warning appears, turn your iPhone off, move it somewhere cooler and out of the sun, and let it cool down.
Install the latest update
Apple’s battery advice starts by making sure you have the latest version of iOS. Go to Settings, General, Software Update, and install any newer iOS 27 release.
Find what’s using your battery
- Go to Settings, Battery, and scroll down to App and System Activity. It lists the share of your charge each app and system task used today.
- For earlier days, tap View All Battery Usage, then tap a day.
- Tap an app to see why. A lot of Background time means it’s busy while you’re not using it. A Cellular Coverage note means it was used on a weak signal, which uses more battery.
Insights and suggestions appear above Daily Usage too, such as turning on Auto-Lock or lowering a high brightness setting.
Stop an app working in the background
- Background App Refresh: go to Settings, General, Background App Refresh, and switch it off for the apps that don’t need it. Tap Background App Refresh at the top to switch it off for every app, or to use it only on Wi-Fi.
- Location: go to Settings, Privacy & Security, Location Services, tap the app, and choose While Using the App, or Never. Leave Location Services itself on. Apple says many features stop working without it.
- Notifications: an app that keeps waking your phone uses battery. Go to Settings, Notifications, tap the app and turn off what you don’t need.
If an app still uses a lot in the background after that, Apple’s advice is simply to use it less.
Use Wi-Fi when you can
Most of the time, Wi-Fi uses less battery than mobile data. A weak signal makes your iPhone work harder to stay connected.
- Join Wi-Fi at home and at work, in Settings, Wi-Fi.
- On iPhone 12 and later, check 5G is on Auto: Settings, Mobile Service (Cellular), Mobile Data Options (Cellular Data Options), Voice & Data, 5G Auto.
- Somewhere with no coverage for a long time? Airplane Mode stops it searching.
The screen
- Dim it. Drag the brightness slider down in Control Centre (Control Center), or go to Settings, Display & Brightness.
- Leave Auto-Brightness on. Apple says turning it off can use more power. It’s in Settings, Accessibility, Display & Text Size.
- Auto-Lock: Settings, Display & Brightness, Auto-Lock. Apple says delaying or preventing it can use more power, so avoid Never.
Power Mode, Adaptive Power and Low Power Mode
Adaptive Power (iPhone 15 Pro and later). Go to Settings, Battery, Power Mode, and check Adaptive Power is on. On days when you’re using more than usual, it extends your battery by lowering the screen brightness a little, letting some activity take longer, and turning on Low Power Mode at 20%. It starts off on iPhone 15 Pro, iPhone 15 Pro Max and iPhone 16 models, including 16e. It’s on from the start on iPhone 17, 17 Pro, 17 Pro Max, iPhone Air, 18 Pro and 18 Pro Max. It needs at least a week to learn your charging habits.
Low Power Mode (any iPhone). It reduces background activity to make the battery last. Turn it on in Settings, Battery, Power Mode, Low Power Mode on iPhone 15 and later, or Settings, Battery, Low Power Mode on iPhone 14 and earlier. It’s in Control Centre (Control Center) too. It switches itself off once your iPhone charges to 80%.
Things that won’t help
- Swiping apps away. Apple says your iPhone manages background apps itself, so quitting apps you’re not using doesn’t make the battery last longer.
- Turning Location Services off altogether. Set the apps that don’t need it to While Using the App or Never instead.
Some videos say to leave it charging overnight so the update finishes sooner. Apple doesn’t say that, though charging overnight is fine.
Check Battery Health
If none of that helps, it may be the battery itself.
- Go to Settings, Battery, then Battery Health on iPhone 15 and later, or Battery Health & Charging on iPhone 14 and earlier.
- Look at Maximum Capacity. It measures how much charge your battery holds compared with when it was new.
iPhone batteries are designed to keep 80% of their capacity after 500 full charge cycles in ideal conditions, or after 1,000 on iPhone 15 and later. The exact figure depends on how your phone is used and charged.
When the battery needs replacing
A new battery should help if any of these is true:
- Maximum Capacity is below 80%.
- Battery Health says Service.
- It says your battery’s health is significantly degraded.
AppleCare replaces the battery at no extra charge if its capacity is below 80%. The one-year warranty also covers a faulty battery, on top of your consumer rights.
Otherwise, Apple’s battery replacement page gives an estimate for your model: UK and US. These were Apple’s out-of-warranty estimates on 2 October 2026:
| iPhone | UK | US |
|---|---|---|
| 18 Pro, 18 Pro Max | £119 | $129 |
| Air, 17 Pro, 17 Pro Max, 16 Pro, 16 Pro Max | £109 | $119 |
| 17, 17e, 16, 16 Plus, 16e, all 15 and 14 models | £95 | $99 |
| All 13 and 12 models, iPhone 11 | £85 | $89 |
| 11 Pro, 11 Pro Max | not listed | $89 |
| SE (2nd and 3rd generation) | £65 | $69 |
Apple confirms the final fee after inspecting your iPhone. The UK page says the fee is subject to VAT and the US page says it may be subject to tax, and a delivery or shipping fee may be added if you post it in. Apple Authorised Service Providers set their own prices. Use Apple or an Authorised Service Provider, so it’s a genuine Apple battery.
If the battery looks healthy and it still drains, contact Apple Support and say what you’ve tried.
Sources
- Apple Support: If the battery in your iPhone or iPad drains too quickly, iPhone battery and performance, Use Low Power Mode, Adaptive Power, battery charge cycles, If your iPhone or iPad gets too hot or too cold, Background App Refresh and closing apps, Location Services and Auto-Brightness.
- iPhone User Guide for iOS 27: battery usage and health, Power Modes, screen brightness, Auto-Lock, notifications, location, updating iOS and quitting apps.
- Apple: battery replacement, UK, battery replacement, US and AppleCare (UK).
HanaHow isn’t affiliated with Apple. iPhone and iOS are trademarks of Apple Inc., registered in the US and other countries.
Read the video transcript
Battery dying since iOS 27? Let's find what's eating it. First, give it a few days. After a big update, your iPhone carries on with update tasks in the background, which uses battery and can make it warm. Apple says to wait a few days, then check again. While that's still going, Settings, Battery may show a card called Ongoing iOS Update, or Ongoing Device Setup. Check General, Software Update for a newer version too. Still draining after that? Stay in Battery and scroll down. App and System Activity shows what used your charge. Tap an app to see why. Lots of background time means it's busy while you're not looking. A weak signal makes it work harder too. For an app that's busy in the background, go to General, Background App Refresh, and switch it off for that app. If it's using your location, go to Privacy and Security, Location Services, and set it to While Using the App, or Never. One thing that won't help: swiping apps away. Apple says your iPhone manages background apps itself, so closing the ones you're not using doesn't save battery. It is satisfying, though. Dimming the screen helps. Apple says turning Auto-Brightness off can use more power, so leave it on. It's in Accessibility, Display and Text Size. Then Battery, Power Mode. On iPhone 15 Pro and later, check Adaptive Power is on. It starts off on iPhone 15 Pro and iPhone 16 models, and it needs about a week to learn your habits. On heavy days it dims the screen a little and limits background activity, and at 20% it can turn on Low Power Mode. On iPhone 14 and earlier, Low Power Mode is right there in Battery. If none of that helps, it may be the battery itself. In Battery, tap Battery Health, or Battery Health and Charging on iPhone 14 and earlier. Look at Maximum Capacity. iPhone batteries are designed to keep 80% after 500 full charge cycles in ideal conditions, or 1,000 on iPhone 15 and later. If it's below 80%, or it says Service, or that its health is significantly degraded, a new battery should help. If you have AppleCare, that's free below 80%. Apple's website gives a price estimate for your model. Our written guide has a fix finder that goes step by step. That's HanaHow. See you next time.
Something not quite right?
Let us know
