Hey guys, i'm a newbie to androidcentral forums.
I've had my Galaxy S5 from Vodafone NL (no vodafone software installed) since one week before official launch (11th of april i think).
The first month the phone was amazing, especially the battery. It would last for almost two days. Suddenly my battery would empty itself from what i've experienced. During the night it would eat a good 15-20% of my charge while it was just sitting there under my pillow (its my alarm). Many days of googling passed and no proper solution or answer, only "your phone might be broken, return it" "might be a dead battery".
My phone lasted less than a day before it needed the electrical syringe from the wall.
But that couldn't and shouldn't be possible, I am not that unlucky (broken battery/broken phone hardware happened to me on my previous phone, htc incredible s).
So i started to look past page 2 on google and then i found some really far fetched attempt for fixing a malfunctioning battery or incorrect calibrated battery. I can't find that damn website, maybe because it was all in russian (translated by google) which makes finding that same website a pain in the ***. I don't save history on my computer because....i have my reasons, now i wish i would have saved the url.
I'll try to explain you how to fix it (or atleast attempt to fix the battery drain). You will be needing a DCV meter, google volt meter, i got the yellow one.
The Galaxy S5 Battery has 2800mAh charge with 4.4V on a full charge, not sure what volts it should be on empty, mine used to be 3.52V. Battery states 3.85V (korean writing), I don't know what that means.
This is all I remember from the website, I'll try to explain with my best english ever I will (broken grammar on purpose

)
1) Charge your phone to 100%. After your phone reached 100%, remove the battery and check the amount of volt. My battery had 4.35V on a full charge. If it is lower than 4.35V (4.31-4.34) your battery holds less charge than a normal battery. If it's lower than 4.30, you should get a new one.
2) Drain your phone battery by playing games or watching movies, till your phone shuts down. Remove your battery and wait 5 minutes. Check your battery volts, mine had 3.52 when it was acting weird. I'm not an expert in batteries maybe someone can explain more about full and empty charges.
3) Insert the battery and turn your phone on, if your phone didn't calibrate the battery correctly you should have atleast 2% of charge in your phone. (i had 4%). Drain the last drops of juice out of your battery and wait for your phone to shut down. Remove your battery again and wait 5 minutes again. Insert your battery and try to turn your phone on. If your phone doesn't turn on procede to 4). If it turns on, drain it.
4) Check your battery Volts, mine had 3.50 exact on a complete drain.
Here comes the weird and how would this ever fix anything part. Drain your phone from excess charge by putting the + and - contacts on the + and - contacts of where you put the battery. Put your DCV meter on 2000m so you can see the amount of charge left in your phone. Mine had atleast 1200 left.
Keep the voltmeter connected to the + and - connectors and you will see the volts dropping graduately. You can speed up the process by putting the voltmeter's + cable between the first and second connector from the phone and the - cable between the third and fourth connector. make sure the voltmeter touches both 1+2 and 3+4. You'll see the volts dropping rappidly till around 15.
5) If the volts wont drop, grab your battery, insert it and directly connect your phone to your charger. If it wont turn on wait untill you see the red light burning. If your phone turns on, let it boot up, enter your pin number and wait 30 sec. After that, turn off your phone and wait till your phone is charged to 100%.
Voila, battery is calibrated and those drain glitches are solved, my battery lasts atleast 30 hours again and I use my phone like an addict (Snapchat, Whatsapp, Family Guy game [this one is a serious battery drainer], browsing ever 30 mins, other apps).
I hope this works for a lot people, trying it wont harm you!