Are you sure that your battery is good? We had an iPhone 5S that seemed to have a good battery but would drop quickly after some usage. The test at the Apple Store did say the battery was defective, even when some outside tools did not.... This weekend, I had 95% on the iPhone battery then had to use an app to configure WiFi hardware. After an hour of this, battery was at 70%. Then I tried FaceTime for 15 minutes... battery warning came up at 10%... got to 8% remaining when FaceTime was ended (total 15 minutes, with max WiFi bars/signal). iCloud syncs 1Password and email on iPhone but none were obviously open/accessed during this.