I recently got a pre-owned iPhone 6s Plus 64GB running iOS 10.1.1, and I've noticed that: When I'm videochatting using Facebook Messenger, the battery drains at a rate of about 1% every 25-30 seconds, while I'm connected to Wi-Fi, at minimum screen brightness. When I open the camera app and shoot pictures, the battery drains at 1% every 1 minute, and 1% every 30-40 seconds while capturing video footage. When I used Snapchat for around 2 minutes, my battery jumped from 32% to 19%. My usage of social media apps are quite minimal, and the Background App Refresh for all of these are turned off. I have the Background App Refresh on only for Gmail. The battery seems alright, at around 2400mAh being it's full charge capacity, which is around 88% of the designed capacity. So, I'm not sure what's wrong, and I'm really looking for some help. Thanks a ton, in advance!