Here's how you can easily disable Bluetooth to preserve your iPhone's battery and make it last longer.
1. Swipe up from the bottom of the screen to open Control Center.
2. Tap the Bluetooth icon to disable it if it's on.
Or you can do it a different way:
1. Go to Settings.
2. Tap on Bluetooth.
3. Toggle the Bluetooth switch to the off position.
Bluetooth can be quite useful at times, but why waste battery power on it if you don't need to?
Additional resources for iOS