My S26 has been draining noticeably faster since moving to One UI 9, even on days when I barely use it. I’ve already checked battery usage, restarted the phone, and given it several normal charge cycles, but nothing obvious is standing out.
I need to decide whether to keep troubleshooting and wait for things to settle down or reset the phone, which is difficult because I rely on it daily and don’t have much time to rebuild my setup. Is anyone else seeing unusual battery drain on an S26 with One UI 9, and did it improve on its own or point to a particular setting or app?
Don’t factory-reset it yet. Try one overnight in airplane mode and another in Safe Mode. If airplane mode fixes the drain, look at weak cellular signal, 5G, or dual-SIM behavior; if Safe Mode fixes it, a third-party app is likely stuck in the background. Post-update optimization can take a few days, but if idle drain stays high after that, waiting through more charge cycles probably won’t change much.
This is more of an update-reset thing as opposed to a battery calibration. Check your always on display, location scanning, performance profile, because sometimes big updates will enable some of those on their own without you knowing.
If it drains overnight in Safe Mode, the update itself is the likely culprit; if it settles down there, a third-party app probably isn’t behaving properly after the upgrade. @not_a_script’s settings checks are worth doing, but I’d run that test before resetting anything. It narrows the cause down quickly without wiping the phone.
Do not confuse the failing night in Safe Mode with the firmware malfunction. By design, this mode disables all apps, with the exception of cellular data, accounts, and various system services, including some Google Play components. A weak signal can also kill the battery at a comparable rate. Thus, the result is not reliable, and you should not jump to conclusions regarding the firmware.
Make sure all updates in the Play Store, Galaxy Store, and Google Play system apps are installed before wiping the cache. Sometimes, significant system updates leave some applications or system services on lower versions, which do not interact well with each other. In addition, rebooting the device is not enough to complete the update process successfully.
In my opinion, you should conduct an additional experiment by turning off the phone on a day when nothing urgent is planned, take screenshots of the battery statistics, signal strength, and top five apps consuming power. If the discharge is still rapid without a particular application, try repeating the test once again and send a bug report directly to Samsung via Samsung Members with system logs attached. This approach, in my opinion, will be much more productive than resetting the phone to factory settings blindly.
Do not forget to try disabling cellular data by switching on the Airplane Mode. However, this method is not universal since several factors affect the discharge rate at once, which is why I am not going to dedicate a long day to testing. If all steps fail, a wipe of the cache and system data would be a more reasonable choice than factory settings.
A phone that stays warm while idle is a different case from one that remains cold while the percentage falls. Warm points to real background activity. Cold with sudden percentage drops can be the battery gauge or an aging cell showing itself after the update.
Try one night with the phone fully powered off. It is not a glamorous diagnostic, but it separates Android drain from battery-level weirdness. If it holds its charge while off, keep looking at software, syncing, or the modem. If it loses a meaningful amount while shut down, a factory reset is unlikely to be the magic cure. Reboot readings can shift slightly, so look for a clear pattern rather than a tiny change.
I’d check whether Battery Protection changed its charging limit too. An update can leave you starting the day with less usable charge than before, which feels like faster drain even when the hourly rate is similar. Compare the actual battery graph over the same screen-off period, not just how early the low-battery warning appears.
The controlled tests suggested here make sense, but I would do the powered-off comparison before wiping caches or resetting the phone. It costs one night and gives you a useful hardware-versus-software clue without deleting anything.
So, don’t trust the battery screen for at least a few days after a jump like this. The usage history is wiped during the upgrade, so the graph is comparing a fresh, half-empty log against your old patterns. That’s enough on its own to make drain look far worse than it is, and half the panic threads I’ve seen on the subject are about a stats screen that hasn’t rebuilt yet.
@phantom_cyber_socket’s warm-versus-cold split is the most useful thing in here, and I’d lean on it harder than the Safe Mode stuff. Temperature tells you more in thirty seconds than a whole night in airplane mode. Warm and idle means something is actually running. Cold with a cliff drop is either the gauge or a cell that’s quietly gotten tired.
Where I would object to this is regarding the purely diagnostic approach. One UI major versions are notorious for enabling new on-device processing, indexing and AI scanning of photos and texts as background processes. The first few days after installing an update are critical as the phone goes through the process of reindexing everything and drains the battery on the way. If your phone is warm at the touch of the night, this would be my first guess before checking the modem or any applications. It should subside as the indexing completes, which takes some time, before attempting any further diagnostics.
The practical solution here is to leave the phone on the charger overnight at least once after the update completes. Navigate to Settings and look for any entries related to media analysis, photo search or assistants that have appeared recently and disable the ones you do not use regularly. This should remedy most cases of post-update battery drain faster and with less hassle than performing a cache clearance. If the issue persists for a few days after the update with no obvious applications hogging the memory and causing the battery to heat up, it is best to contact Samsung support directly. Do not factory reset your phone over a several-hour-long battery graph, especially if it barely had time to populate.
The hidden catch is that the battery page shows each app’s share of power used, not how many battery percentage points it consumed. That confused me at first and can make an innocent app look guilty.
Check Background usage limits and Unrestricted battery access. A major update can change which apps are sleeping or optimized. Move nonessential apps back to optimized, but avoid restricting messaging, alarm, or health apps unless delayed notifications are acceptable.
Change one setting at a time and compare similar screen-off periods. If you adjust everything together and the drain improves, you still won’t know what caused it.
A VPN, ad blocker, work profile, or accessibility service can keep the phone awake while the battery page blames “Android System” or “Google Play services.” That makes the app percentages @looppro described even less useful after a major update.
Turn off such services for a period of time when a phone is normally turned off. After that, analyze whether there is a decrease in time consumption compared to similar indicators before. If it is, update or reinstall that application instead of adjusting dozens of different settings. If there is still nothing in common, maybe Android System has a huge amount of time spent in background, meaning that something with processes was broken up.