[Galaxy Tab 4 Android Development] IamTheBRAVE:
Sorry for the late reply.

I've had the same problem for more than 6 months. Battery would lose 60% in less than 15mn, a reboot to recovery sets it back to 90% which sticks when back in Android system.

I have the 3g T531 model with sim card support and that's the very heart of the problem.

After a long period of observation and monitoring (with SystemPanel2), I found a least 2 or 3 bugs.

1. I noticed that my CPU was stuck in performance governor (@frequency 1200 MHz 24/7/365) which harms the battery in the long run. That may have happened after I messed things with Kernel Adiutor. Trying to set things back with that same app was not successful, and no other app like setCpu could do it. The governor sticks on reboot. [Solution at the end of this post]

2. Second bug has to do with RIL service running and not finding a sim card or IMEI wiped (3rd bug). It runs qmux service which uses a lot of CPU and battery trying to connect. The only solution is to disable qmux on boot (if no network is available because of no sim/no IMEI.) [Solution at the end of this post]

The problem is sticking through multiple C.Roms - Crdroid 7.1 - LineageOs 14...) When using a sim there's no problem (not possible on custom ROMs, never been able to make sim work on them (see 3rd bug). Only stock 5.02 ROM has no battery drain)

3. Third bug has to do with EFS/IMEI being wiped after flashing with TWRP. This is either twrp's fault ( a known bug corrupts EFS partition if you try backing up.) What I noticed is when installing stock 5.02 firmware, all partitions are working as intended. If I flash a custom ROM - Android 6 and up- , some partitions are wiped : EFS (part. 11) modemst1&2 (part 12&13) param (part 18) and also FSG, which is a golden backup of EFS data. They're no longer visible with es file explorer or recovery file manager. Therefore I get an IMEI 0, Baseband unknown, wifi and Bluetooth random disconnect.

Right now, I'm still trying to fix this one. It so happened that I received a free sim card from my operator and that's when found I had no EFS partition on MM and N. And I had no backup of those partitions. After researching, using EFSBackUpPro is the only way. I reverted to stock 5.02, made a backup of all my partition (recommended to do it anyway if you're lucky enough not to have all these problems) and now I'm gonna try to flash a C.Rom (my favorite is crdroid) then restore partitions with EFSBackUpPro (not Twrp, not trusting it anymore till there a newer version with confirmed fix- my version is 3.0.0.9)

What I'm not sure about is whether partitions backup made in 5.02 will be useable in 7.1.1. Technically, AFAIK EFS data folder is not system related. It holds NV data, necessary for setting up the sim and IMEI (no IMEI changer app will work because partitions are corrupt) some people with other phones reported that connectivity and IMEI data were restored after copy pasting FSG partition file without need of a reboot. Gonna test this in the following days.

Now onto the solution. We're gonna use the same file for both problems. Of course only add the lines related to your problem.

a) With es file explorer, locate init.rc in root folder, open it in txt editor and look for:

on property:setprop ro.radio.noril yes

Stop qmuxd

Stop netmngrd

Don't know if this is necessary but remove the last line ( so netmngrd is not disabled. AFAIK, it's responsible for managing networks incl. Wifi & BT, so you'll still need it)

b) locate /etc/init.d/90userinit and edit it adding:

setprop ro.radio.noril yes

setprop hw.nophone true

This will disable qmux and tell the system you don't have a phone. This fix worked for me for the time I had nougat still installed. I had to revert to LL to solve my EFS/no sim detected bug.

For the governor stuck on performance, add the following line in the same file:

echo ondemand > /sys/devices/system/cpu/cpu0/cpufreq/scaling_governor

You can use interactive if you want but ondemand is more stable.This will apply ondemand governor on the first core of the CPU which is supposed to take the main workload of the system. The other cores help with the minimal work, they go offline when they finish their work.

That's it! Hope this will help someone. Click on thanks if it did.

Happy Holidays??