[Galaxy S II Q&A, Help & Troubleshooting] ido4444:
Intro

Hello I'm a very old lurker in this forum yet a new member and this is my first post so please don't kill me if I failed to follow the rules or if my English sucks. I will try to organize this thread and make it clear and easy to understand and read, while providing as much information as I can.

The Problem

So my i9100 has been having extreme battery drain lately, about 2% per 3 minutes. I refrain from using it throughout the day to help my battery hold until night. When I do so, it is usually about 40% by the time I go to sleep with having BARELY used the phone. Probably just now and then to answer a Whatsapp message or to check the time. I've long ago uninstalled all games since I can't even think of playing games with this horrible battery status.

How it started

The last thing I can remember before starting to have this problem is about a year(?) ago when I was on Jellybam. I had good battery, and then a build with an excellent battery came out and it worked perfectly. I can't remember which version it was, but a little after that, I updated Jellybam and noticed SUPER battery drain. I waited a little for the next updates but it wasn't fixed, so I changed a ROM. I noticed that it wasn't helping. So I tried the following for a couple of months now:

Attempts To Solve The Problem

I have tried the following:

Using lowest screen brightness

Disabling obvious stuff like GPS, Bluetooth, Wifi, 3G

Closing or even NOT installing any known battery consuming apps

NOT using task killers

USING task killers

Underclocking

Removing widgets. Using least icons possible on launcher

Using many different launchers

Changing ROMs, kernels and both

Reverting back to stock

Buying a new battery (extended and not original)

Trying a new original battery from a friend who has i9100

Flashing modems and RILs, including GetRIL. In fact, I've had better battery with worse signal (but not always). I think it was with XXLPH or XXLPW.

Using battery savers like JuiceDefender which basically do everything I've already tried. What's a smartphone without internet

Using BetterBatteryStats and Gsam Battery Monitor Pro. Did not notice anything special (but I am not pro enough to understand everything on BBS, though I googled some of the things and haven't noticed something unusual). Maybe some pro can help me with it.

Assumptions / Notes

A couple of versions ago, I have used Omega ROM version 4.2.1 which suddenly fixed(?!) my battery. I can't remember which build it was, but the new one doesn't fix the battery drain. I assume it could be due to the radio update to XXMS2

I have a feeling that the drain is related to the modem (aka baseband), because I've had some more battery-friendly modems and some less

I have tried many modems that are supposed to work perfectly (and really gave me good connection speed and signal), but they did not fix the battery drain. Even on stock rom

My provider is Golan Telecom, which is supposed to work good with Cellcom modems, but it didn't. At least not battery-wise

Last resort can be taking it to a lab, but it's hard for me to stay without my phone, and I think people here are more skilled than the noobs in the lab.

Can the problem be hardware-related but not battery-related? May it be caused by the huge amount of times I've flashed ROMs and kernels?

Had my phone for around 2 years

Never bricked my phone

Sorry for being a burden to this forum with this first post of mine, but thanks a TON of anyone who can shed some light on this problem for me!

*I have attached one log of BBS