My galaxy S4 battery is draining quick.

[wildfire04]

Hey all, I'm new here... I recently bought an s4 i9500(45 days back) and it's battery life is very low, then I updated it to cm12.1 and it sucks even more.. I checked every background task to see where the problem is but I can't find any.. Do you think my battery is spoiled or is its life really bad? How long does your i9500 last on a full charge with cm12.1?
Here are some screen snaps I barely used it with very low brightness. This was my battery stats from 100%

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[Rukbat]

1. How old is the battery?

2. How low do you normally let it discharge before charging it?

(I suspect that you regularly discharge it well below 40%, and that it's a couple of years old, which would combine to make it a battery on its last legs. They're cheap, though.)