What is draining my Android battery?

To find a battery drain, look at the rate (milliamp-hours per hour) over a long enough window, not just the total, and look for apps that stay awake: wakelocks, sensor polling and background jobs.

Updated 2026-11-01

Why the battery screen can mislead

Android's statistics cover the time since the last charge, so a long window and a short window are not comparable.
Totals hide the story: an app that ran for ten minutes at high power and one that quietly runs all day can use the same mAh.
Right after charging the window is only seconds long. A rate computed from it is meaningless, and slimdroid says so instead of showing one.

What usually causes a drain

Apps that hold a wakelock and stop the phone from sleeping.
Sensors polled constantly: location, motion and other sensors, often by background services.
Background jobs and sync that run far more often than needed.
Preinstalled services that you never use but cannot see.
A weak mobile signal: the radio works harder to stay connected.

How to measure it

adb shell dumpsys batterystats            # per-app power since last charge
adb shell dumpsys deviceidle whitelist    # apps exempt from Doze
adb shell dumpsys sensorservice           # who is using sensors

The slimdroid tool reads these dumps, converts them to mAh per hour and lists sensor pollers and Doze-exempt apps, with the app's purpose beside each one. Scan after the phone has been unplugged for several hours for a meaningful rate.

What to do about it

Set heavy background apps to Restricted or Optimised in Settings > Apps > Battery.
Revoke location and sensor permissions that an app does not need.
Disable preinstalled apps you never use (guide).
Compare a scan before and after to confirm the change worked.

How much overnight drain is normal?

A healthy phone on standby loses only a few percent overnight. If it loses ten percent or more, something is keeping it awake.

Does Doze exemption matter?

Yes. Apps exempt from Doze can run in the background while the phone is idle, so each one on that list is a possible drain.