Before blaming iOS 9, go to the Apple Support battery repair page and have your 5S tested. It may just be a coincidence. My 5S's battery turned out to be at end of life and couldn't hold a charge anymore. The expected useful lifetime of the batteries are roughly 2 years. https://www.apple.com/support/iphone/repair/battery-power/
Topic:
App & System Services
SubTopic:
Core OS
Tags: