You may not know that on iOS 8.2, a feature called Fitness Tracking is integrated by default into the device, which is the main reason causing rapid battery drain. To resolve this issue, you still have the following steps to follow:
Guide to Fix Battery Drain Issue on iPhone 6 Running iOS 8.2
Step 1: Access Settings.
Step 2: Proceed to Privacy.
Step 3: Scroll down and locate the Motion & Fitness section, then select it.
Step 4: The toggle switch is currently set to ON, switch it to OFF if you don't need this feature.
https://Mytour.vn/khac-phuc-loi-hao-pin-tren-iphone-6-chay-ios-82-2101n.aspx
For users in Vietnam, functions related to health or smart watches are less of a concern, so such applications can really drain your phone's battery quickly with unnecessary tasks. Follow the instructions above to turn off this feature.
