What can I do about overnight battery drain showing system as the culprit?

[William_S]

My new phone’s battery drains almost 20% overnight with everything closed and Wi-Fi off. I’ve checked the battery usage stats, and it just shows “System” as the main culprit, which isn’t very helpful.

[Amelia54]

That happened to me last year. I chased apps and settings, but the drain was a wakelock from a core service. After a week of weird dips I did a factory reset and it seemed to help for a while.

[Avery_M]

I swear I tried turning off background data and limiting syncing, yet the drain stayed around that 20 mark and System stayed on top in the stats. It felt like the OS itself was chewing through power.

[Chloe90]

Have you checked whether a recent software update is stuck in a loop or if the battery health is bad?

[Steven.W]

When I logged the overnight drain, I noticed it mostly happened during the deep sleep window with no network activity. It didn’t happen every night, which made me doubt a simple culprit.

[Penelope.J]

I also tried calibrating once by letting it run down and charging full, but I didn’t see a lasting change. It left me unsure if the problem was hardware or software.