I was having all sorts of battery issues after the 09/26 update. Hot phone, 8-10 hours to 5%, checked thru the forums, tried various battery xxx apps, and so on. Lots of pruning and sniffing got it somewhat better. Didn't see much change dumping Google or Amazon stuff, tho there was a Samsung push-type app for something I never used/needed that was eating up 20%, sometimes. (Can't remember it's exact stats. It's gone, good riddance!)
After lots of attempts, app shut downs, setting tweaks and all that, it got better, but was still way off what it used to be. (Got up to 14-16 hrs, to 20% or so.)
Then saw someone mention Macrodroid and shutting down the radios. Picked up the paid app, wrote a few macros and gave it a try. Just shutting down Wi-fi and data radios when the screen's off has worked wonders. (Phone's at 98% now, afterr 2 hours on battery, couple Email (When on charge it leaves wifi on, so the email updates, not a big deal, but figured why not leave radio on if powered?) and text msg checks, BT is on and attached. Built a macro so my navigation app will keep the data modem on for updates, but nothing else is annoyed, and I can go all day with several calls, Email checks and general quicky Web lookups, and be over 80, maybe even up to 90% of batt life remaining after 12 hours. Much better. Takes a couple secs to connect wifi when the screen's up, but doesn't impede my usage at all.
Once in a while, there'll be some app that goes wonky or such, and will keep the phone awake, sucking the juice. (Message app, email app, navigation app, couple others over the past month.) If I see something happening, shut it down. Might experiment with macros to shut down background things as well. The biggest change was definitely Macrodroid, which also helped my brother's Moto mini with drain issues. Nice stuff. Bluetooth was designed from the ground up to be miserly, and I use it several hours daily. WiFi, OTOH, wasn't designed with battery miser in mind. Even if I'm within 30 feet of the router, 95% of the time, it still is thirsty.
At least I can depend on my phone again, and actually use all the features I like.
Thanks to whomever mentioned MacroDroid!
Good luck, people. The S5 is a great phone, it's been serving me well.
Yours, Stu. (Electronic tech, been working on tubes, transistors and microprocessors for decades. First wireless phones I repaired were RCC (Radio Common Carrier), used an operator, were trunk mounted and had tubes...)