Having a service or system that is responsible for automatically downloading files, applications, or to be responsible to check if an update of one of the many apps you may have installed on our device causes the processor time is wasted on these tasks, besides spending some battery.
From my perspective the biggest spender is the continuous search for application updates, but we can keep to our liking and according to the needs we have at that moment battery saver.
Step 1. We go into settings and look for iTunes Store
Step 1E seek the option settings within iTunes Store
Step 2. We disabled the automatic update options
Step 2E We disabled the automatic updates and the rest who want to take off
With these settings, your phone should return to what it was, and its battery consumption to be reduced much back to normal.