Well, my S4 Mini has most weird behaviour I met that can't understand. When the power was under 50% the phone battery drained more rapidly than above 50%. I cant see there were any apps or processes that could be cause wakelocks from bettery stats. I initiallybelieved that the stock battery have problem, so I swap my addictional battery(have confirmed it worked awesome) bought from MPJ last month, the battery drain issue persists.
Also during the night, my phone drained like 18%-23% in offline if the battery leave above 50% or more no drain happens. I've googled and this problem finally solved by flashing the arco's kernel in rootkit_v2. Even though i still not underdand why...
So what are the most weird thing on your phone? Just curious:)
"When the power was under 50% the phone battery drained more rapidly than above 50%"
Lol, sounds like my car's fuel reservoir though I'm pretty that's in my head too so you probably have the same problem. Try a battery preserving app like juice defender, it works...wonders, try it and you will see what I'm talking about, it will double your phone's battery lifetime.
It's good that my S4 mini does not have the battery problem like yours..lol... but still extra battery is my must. Even though I got one already, now thinking the second...
Normal battrery usage, as voltage gets lower (that battery gets flatter) then curent draw increases to get the same power out of it. I don't know how phones utilise the battery, but I would consider it normal.