Recently, my iPhone battery started to rapidly decline. In the past if I wasn't on calls, it would last a day or more with a recharge. Now it was lasting an hour or two. I figured I would have to go and get a replacement battery - and I've only had the phone a year.
However, before I trekked down to the ATT store, I decided to poke around Google and see if there were some known issues with my 5C phone. What I found was a software fix - and it worked like a charm.
Basically, I went into settings and clicked General - Reset - Reset all Settings. It doesn't clear out apps so no problem there. Then I powered off the device, and plugged it into a wire connected to power and not my PC. It charged overnight and the problem went away. This may not work for everyone but it saved me a $49 new battery. Patty likey.