Sudden power off when battery is less than 50 percent

Hi community,

I would be glad to get any help for the problem below. Or maybe you can guide me how to provide more information to investigate it.

Problem

• The phone sometimes powers itself off abruptly which can lead to database corruption. So it is very annoying...


• However, it only seems to occur in some cases:


• It happens as soon as battery is below 50% (this is not exact, but pretty close)


• It only happens when the screen is off. May happen after 30 sec to 5 min.


• It never happens when a USB cable is connected (power-only or computer)


• It does not seem to happen when a "background task" is running


• In some rare cases, it does not happen at all, or maybe just has not happened for a longer period of time. I could not determine what is different about the state of the phone then. When I turn the screen on once, and off again, the chances are high that it will power off very soon!

By "background task" I mean something like playing music, but I can not exactly define it. It can stay on like for one hour without any problems (screen turned off). It also stays on when, for instance, the timer is running and the screen is on.

So it does not seem to be a problem of the battery...

ROMs

I tried the following ROMs, all with the same issue. When switching ROMs, I always wiped system, data, cache, dalvik-cache. Never flashed another Zip on top (like Gapps).

• Two official versions of cm12.1


• A BlissPop v3.9 earlier build than below


• BlissPop-v3.9-m8-OFFICIAL-20150827-0154 (currently running)


• SkyBliss-v3.2.1-m8 (fantastic ROM, btw!)


• Stock v4.19.111.2 + OTA to v4.19.111.3

More details of stock:

1. Relocked and flashed the Firmware v4.19.111.2 (Android File Host fid=95916177934521492)


2. Unlocked, flashed TWRP, then Stock v4.19.111.2 (Android File Host fid=95916177934527598)


3. Relocked and receive OTA v4.19.111.3

Troubleshooting

I had CatLog record some sessions (flush after 1 line). There was never anything suspicious in the logs.

I changed the CPU governor in my current BlissPop ROM: was Lionheart, tried Ondemand, Intellidemand, and Interactive. Subjectively, it slightly reduced the amount of battery percentage when the problem begins to occur. However, the problem persists and I did not take note of the battery charge.

Left default setting for "power safer".

???

What can I do about it?
Are there any tools to investigate the problem in more detail?
Has anyone the same problem?



Thanks a lot,
Adi