Updating android phone
Happily, newer iterations of the Android OS have introduced battery saver features that economized how various apps use up juice.
If you can't get a signal, turn on Airplane Mode by swiping down and tapping the Settings wheel.
Though Doze, which prevents your phone from sending and receiving data, is a default feature on Android Marshmallow and Nougat, users of Android 4.1 (and newer) phones can download a separate, more powerful app called Doze (free in Google Play).
Once downloaded, the app needs to activated, then it works in the background (without affecting Doze mode, if it's downloaded onto a Marshmallow phone).
Some apps track your location and therefore use more battery power than strictly necessary by accessing your GPS.
At Settings Location you can see which apps recently requested your location, as well as how much (low/high) battery it took.
On the flip side, disabling Wi-Fi may not always save battery life.