When your iPhone drops 20–50% overnight
If your iPhone is losing a big chunk of battery while you sleep, it’s almost never “normal standby”. True idle drain is usually a few percent over several hours. When you see 15%, 30% or more gone by morning, something kept the phone awake: a rogue app, a stuck background task, a poor network loop, or a system service that’s misbehaving.
The good news is you can usually identify the culprit with built-in tools. The key is to separate screen-off battery use from screen-on use, then confirm whether the phone is actually sleeping or repeatedly waking.
I see this most often after an iOS update, after restoring from iCloud, or when people change routers or SIM plans and the phone starts hunting for a stable connection overnight.
What “overnight drain” really means (and what to measure)
Standby vs background activity
Even with the screen off, iOS can run tasks: iCloud sync, photo analysis, mail fetch, app refresh, location updates, and push notifications. That’s normal in small bursts. Overnight drain becomes a problem when those bursts never stop, or when the phone can’t complete a task and retries for hours.
In practice, the fastest way to stop the drain is to find what’s consuming battery during screen-off time, not to guess based on what you used during the day.
Use Battery charts the right way
Go to Settings > Battery and look at the last 24 hours. Tap the chart bars covering the time you were asleep. You’re looking for two things:
- Battery level line: a steady slope down suggests continuous drain; sharp drops suggest periodic wakeups or a single heavy event.
- Activity (screen on/off): if there’s significant screen-off activity overnight, something is running when it shouldn’t.
Then scroll down to the app list and check whether any app shows high usage with the screen off. If an app is top of the list overnight, it’s your first suspect even if you barely used it.
Confirm whether the phone is waking repeatedly
A common pattern is a phone that never fully idles because it’s stuck in a network loop (Wi‑Fi reconnects, VPN reconnects, push retries) or a background sync loop (Photos, Mail, cloud storage apps). You’ll often see:
- Battery dropping steadily with screen-off activity present.
- Wi‑Fi or mobile signal fluctuating overnight.
- Warmth around the top/back of the phone in the morning even though you didn’t use it.
This is the most common issue I see on devices sold in the UK before 2024 when they’re paired with older routers that aggressively roam or use band-steering poorly.
Why iPhones drain overnight: the usual technical causes
1) Poor Wi‑Fi or mobile signal causing retry storms
If your iPhone sits in a weak Wi‑Fi area overnight, it may keep reconnecting, renegotiating, and retrying background transfers. If Wi‑Fi is off or unstable, it may fall back to mobile data and do the same. Either way, radio activity is expensive.
If you’ve also got a VPN profile enabled, the phone can get stuck trying to re-establish tunnels in the background. I’ve seen this drain a healthy battery surprisingly fast even with the screen off.
2) iCloud Photos, backups, and post-update housekeeping
After iOS updates, restores, or enabling iCloud Photos, iOS may spend nights indexing, analysing photos, syncing metadata, and finishing background tasks. This should settle after a day or two, but sometimes it gets stuck.
When it’s stuck, you’ll see high screen-off activity with system services rather than a single third-party app. It’s not always obvious in the app list, so you need to use elimination steps.
3) Misbehaving apps with background permissions
Social apps, mail clients, fitness trackers, smart home apps, and anything with location permissions can keep waking the phone. The worst offenders are apps that combine Background App Refresh, Location, and Notifications—they can create a constant trickle of work.
In practice, disabling background refresh for the top 1–3 offenders fixes the problem in about half of cases.
4) Bluetooth accessories and flaky device handoffs
Some Bluetooth devices repeatedly reconnect (car kits, older earbuds, trackers). That can keep the Bluetooth stack busy and trigger wakeups. It’s less common than Wi‑Fi issues, but when it happens the pattern is consistent: drain is worse on nights you’re near the accessory.
5) Battery health and temperature effects
If your battery health is degraded, the same background activity produces a larger percentage drop. Also, charging overnight in a warm spot (on bedding, near a radiator) can lead to heat, which increases background power use and reduces charging efficiency.
Battery health doesn’t usually cause sudden overnight drain by itself; it just makes existing drain more obvious.
A diagnostic flow that actually isolates the cause
Work through these steps in order. Don’t change ten settings at once; you want to learn what fixed it.
Step 1: Check Battery Health and charging behaviour
- Go to Settings > Battery > Battery Health & Charging.
- Check Maximum Capacity and whether it says Peak Performance Capability.
- Confirm whether Optimised Battery Charging is enabled (fine to keep on).
If maximum capacity is very low, your “overnight drop” will look dramatic even when the phone is behaving normally. I rarely see overnight drain complaints disappear completely until the battery is replaced when capacity is heavily degraded.
Step 2: Identify screen-off offenders in Battery
- Open Settings > Battery.
- Tap the overnight time window in the chart.
- Look for apps showing high usage with screen off.
If one app dominates, focus on it first: update it, force close it, then restrict its background permissions (steps below). If the list is mostly system items, skip ahead to the network and reset steps.
Step 3: Disable Background App Refresh for the top offenders
- Go to Settings > General > Background App Refresh.
- Either set it to Off temporarily, or disable it per-app for the worst offenders.
Leave it off overnight and compare the Battery chart the next morning. If drain improves, re-enable it only for apps that genuinely need it (messaging is usually fine; social feeds rarely are).
Step 4: Tighten Location Services (without breaking essentials)
- Go to Settings > Privacy & Security > Location Services.
- For apps you don’t need tracking you overnight, set to Never or While Using.
- Open System Services and disable non-essential items you don’t use (for many people, turning off location-based suggestions helps).
Don’t disable core items blindly. The goal is to stop apps from waking the phone in the background, not to break Find My or emergency features.
Step 5: Stop network loops (the most overlooked fix)
Network instability is a classic cause of overnight drain because iOS keeps retrying “small” tasks that never complete.
- Toggle Airplane Mode for 10 seconds, then turn it off.
- If you use Wi‑Fi at night, toggle Wi‑Fi off/on.
- Go to Settings > Wi‑Fi and tap the (i) on your home network, then:
- Disable Low Data Mode unless you need it.
- Disable Private Wi‑Fi Address temporarily if your router is older and struggles with it (test for one night).
If your iPhone also drops Wi‑Fi randomly during the day, fix that first; overnight drain often disappears once the connection is stable. See Fix iPhone Wi‑Fi randomly disconnecting at home.
For Apple’s official steps on checking battery usage and settings, use Apple’s guide to checking iPhone battery usage and health.
Step 6: Turn off always-on features that keep the phone “busy”
These aren’t always the root cause, but they’re good for isolating the problem.
- Always-On Display (supported models): disable for one night.
- Raise to Wake: disable if you keep the phone on a moving surface (bedside table that gets bumped).
- Hey Siri: rarely the cause, but if you suspect constant wakeups, disable temporarily.
- Widgets / Live Activities: remove any that update frequently (sports, delivery tracking).
I’ve seen Live Activities cause unexpected background churn when an app’s server keeps pushing updates that never settle.
Step 7: Check Mail and calendar fetch settings
- Go to Settings > Apps > Mail > Mail Accounts > Fetch New Data.
- Set Push off temporarily and use Fetch every 30 minutes or hourly.
If you have multiple accounts (work + personal), one misconfigured mailbox can keep retrying. This is especially common with older IMAP setups.
Step 8: Force a clean restart (it matters more than people think)
A stuck process can survive for days. A restart clears it.
- iPhones with Face ID: press Volume Up, press Volume Down, then hold Side button until Apple logo.
- iPhones with Home button: hold Side/Top button until power off slider, then turn back on.
In real troubleshooting, a restart fixes “mystery drain” often enough that I do it early, not as a last resort.
Step 9: Update iOS and apps (but don’t assume updates are the cure)
- Settings > General > Software Update and install the latest iOS point release.
- Update apps in the App Store, especially anything that appears in Battery as a top consumer.
Point releases frequently patch background crashes and runaway tasks. But if your drain started right after an update, you still need to do the battery chart checks—updates can also trigger indexing that looks like a fault for a night or two.
Step 10: Reset Network Settings if the pattern screams “connectivity”
If your overnight chart shows constant screen-off activity and you’ve noticed Wi‑Fi weirdness, reset network settings.
- Go to Settings > General > Transfer or Reset iPhone > Reset.
- Tap Reset Network Settings.
This removes saved Wi‑Fi networks and VPN settings, so you’ll need to rejoin Wi‑Fi and reconfigure VPN. It’s worth it when the phone is stuck in a reconnect loop.
Step 11: Last resort—settings reset or full restore (only after you’ve measured)
If you’ve identified no clear offender and the drain persists for several nights, you can try:
- Reset All Settings (doesn’t erase data, but resets preferences).
- A full backup and restore, ideally setting up as new if you suspect a corrupted migration.
I don’t jump to a full restore unless the Battery chart stays abnormal after network reset and background permissions are tightened, because restores cost time and often don’t fix a simple app-level problem.
Real-world overnight drain patterns (and what fixed them)
Scenario A: “It only drains badly at home, not at hotels”
This usually points to your home Wi‑Fi environment rather than the phone. I’ve seen mesh systems with aggressive band steering keep iPhones bouncing between nodes, especially if the phone is on a bedside table at the edge of coverage.
- Fix: lock the phone to a stronger node by moving the mesh unit, or disable features like “smart connect” on some routers.
- Quick test: turn Wi‑Fi off overnight and see if drain improves; if it does, the Wi‑Fi environment is the trigger.
If your router restarts or renegotiates overnight, that can also trigger repeated reconnects. If that’s happening, it’s worth checking Fix router restarting randomly every night.
Scenario B: “Battery drain started after iOS update”
Two common causes: post-update indexing (temporary) and a third-party app that hasn’t updated yet (persistent). The Battery chart tells you which.
- If you see heavy activity for one or two nights and then it settles, that’s normal housekeeping.
- If the same app is top of screen-off usage every night, disable its background refresh and update it.
This is the most common issue I see on devices that were restored from iCloud immediately after updating, because the phone tries to sync everything at once.
Scenario C: “It drains even in Airplane Mode”
If Airplane Mode doesn’t change the drain, the culprit is usually local: a stuck app, a system service, or a hardware issue.
- Fix: restart, then test one night with Background App Refresh off and Location restricted.
- If it still drains, check Battery Health and consider a battery replacement.
When Airplane Mode doesn’t help and the phone is warm in the morning, I start suspecting a runaway process or a battery that’s reached the end of its useful life.
Scenario D: “It’s fine until I connect my Apple Watch / car Bluetooth”
Repeated Bluetooth reconnects can keep the phone awake. This is more common with older car kits and some third-party wearables.
- Fix: forget the Bluetooth device and re-pair it.
- Test: turn Bluetooth off overnight for one night and compare the Battery chart.
I rarely see this on newer accessories, but older in-car systems can be surprisingly noisy in the background.
Mistakes that make overnight drain worse
- Changing lots of settings at once: you lose the ability to identify the real cause.
- Assuming “battery health is fine” because the phone charges to 100%: capacity and performance under load are the real issues.
- Leaving a VPN always on when the server is unstable: the phone will keep trying to reconnect.
- Using weak chargers/cables that don’t reliably charge overnight: you wake up with less battery and blame “drain”.
- Charging under a pillow or on thick bedding: heat increases losses and can pause charging.
In practice, the “it drained overnight” complaint is sometimes “it didn’t actually charge properly overnight”, so always confirm the phone reached and stayed near your target percentage.
Practical tweaks and kit that reduce overnight drain
Use a stable charging setup (to remove variables)
If you’re troubleshooting, remove charging uncertainty: use a known-good wall charger and cable for a few nights. A flaky cable can cause micro-disconnects that stop charging, then the phone runs down normally and looks like it drained.
If you prefer wireless charging, use a consistent pad that doesn’t overheat the phone. A Qi2-compatible wireless charging pad is a simple way to reduce alignment issues that cause slow or interrupted charging overnight.
Set a “sleep profile” that reduces background noise
- Enable Sleep Focus to reduce notification wakeups.
- Disable non-essential app notifications that light up the screen.
- Keep the phone face down if you use Raise to Wake and get accidental screen-ons.
This doesn’t fix a runaway background task, but it does cut down on small wakeups that add up in real homes, not lab setups.
Know when to stop tweaking and replace the battery
If your maximum capacity is low and you’ve confirmed abnormal drain across multiple nights, a battery replacement is often the cleanest fix. You can chase settings forever, but a tired battery makes every background task look worse.
For Microsoft 365 or Google accounts that keep re-authing and draining battery, it’s worth checking the account sync guidance too; see Google’s help page for fixing sync problems on iPhone and iPad.
Wrap-up: the fastest path to a normal morning battery
Start with measurement: Battery charts during your sleep window. If you see high screen-off activity, restrict background refresh and location for the top offenders. If the pattern looks like constant reconnecting, focus on Wi‑Fi/mobile stability and consider resetting network settings.
When you change one thing per night and compare charts, the cause usually becomes obvious within two or three mornings. That’s how you get from “mystery drain” to a stable iPhone that holds charge overnight.
FAQ: awkward overnight drain cases people actually hit
Why does my iPhone battery drain overnight only on my home Wi‑Fi (UK), but not on 4G/5G?
This usually means your phone is stuck reconnecting to home Wi‑Fi or bouncing between mesh nodes. In real homes, band steering and weak signal at the bedside are the biggest triggers. Test one night with Wi‑Fi off; if drain improves, fix the Wi‑Fi stability (router placement, mesh settings, or reset network settings on the iPhone).
My iPhone shows “No Cell Coverage” at night—can that drain the battery?
Yes. When signal is poor, the modem works harder and retries connections, which can keep the phone from idling properly. This is the most common issue I see in older UK buildings with thick walls where the phone sits in a dead spot overnight. Try Wi‑Fi calling (if supported), move the phone, or use Airplane Mode with Wi‑Fi on as a test.
Why does my iPhone battery drain overnight even when I don’t touch it and the screen stays off?
Screen-off drain is almost always background work: sync, location, push notifications, or a stuck app. Check Settings > Battery and tap the overnight window to see screen-off activity. If one app is high, disable its Background App Refresh and restrict location to While Using.
After updating to iOS, my battery drains overnight for two nights—should I worry?
Not immediately. Post-update indexing and iCloud sync can run for a day or two, especially if you have lots of photos. If the drain continues beyond a few nights or one app dominates screen-off usage every night, that’s when you treat it as a fault and start disabling background permissions.
Why does my iPhone drain overnight while charging on a wireless pad?
Most of the time it isn’t “draining”; it’s charging slowly or intermittently due to heat or poor alignment. If the phone gets warm, iOS can slow or pause charging, and you wake up with less than expected. Test with a wired charger for two nights to remove variables, then revisit the wireless setup if the problem disappears.
Recommended gear on Amazon UK
- A Qi2 wireless charging pad helps when overnight “drain” is really intermittent charging from poor alignment or heat on older wireless pads. View Qi2 wireless charging pad on Amazon UK
- A 20W USB-C PD wall charger is useful for troubleshooting because it removes slow, unstable charging as a variable when you’re measuring true overnight drain. View 20W USB-C wall charger on Amazon UK
- A reliable USB-C to USB-C cable helps in setups where overnight charging stops due to cable dropouts, which can look exactly like battery draining while idle. View USB-C to USB-C cable on Amazon UK
- A dependable Lightning to USB-C cable helps older iPhones where overnight charge percentage is inconsistent because the cable or connector fit is slightly unstable. View Lightning to USB-C cable on Amazon UK
