Why is my iPhone 5s battery dying so fast all of a sudden?

Since the new iOS 8.0.2 my battery has been draining so fast. Literally every 2 minutes my battery percentage lowers by one. I close all my apps and it still lowers very fast. I never had this problem in the past but now it's dying so fast please help

Redo all your settings, maybe it reset everything? Either way it wouldn't drop that fast.

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