I have a used Samsung Galaxy S3 Mini GT-I8190. When I shut down the phone the battery still drains. The longer I leave the battery in the shut down phone the more charge it looses. Typically the battery looses between 1% and 2% charge per hour when inside the shut down phone. After a few days without turning the fully charged phone on the battery is completely dead so that I cannot turn on the phone again without charging first.
I don't know the previous owner and cannot ask them if they had the same problem.
Things I tried so far:
- Tried to spin the battery on a table to see if the battery is bloated. The battery did not spin at all. Its completely flat on both sides.
- Removed the fully charged battery from the phone, let it sit outside for a few days, put it back in, turned on the phone to read the battery level: The battery was still full – so the battery shouldn't be the problem.
- Bought a new battery from another vendor anyways and did the same tests as before.
- Factory reset (multiple times)
- Update to the latest available OS (Android 4.1.2) provided by the vendor.
- Update to the latest available custom ROM (Lineage OS 14.1 / Android 7.1.2).
- After the factory resets and after flashing I did not install or customize anything apart from the following things. Of course, they had no effect since the phone was turned off — I read about these things in some forums and tried them anyway.
- Only on the vendor's OS: Stop the pre-installed Mail service (even though I didn't sign into anything).
- Turn off everything (Wifi, GPS, ...)
- Enable (extreme) power save mode
Neither did I insert a SIM card nor an SD card into the phone, so these two can also be ruled out as the culprit.
Why does the battery drain when the phone is shut down?
Can I do anything about this?