With this device I've never found it necessary to use anything, like others have stated, I think the battery life is great. In the past, on previous phones, I found that by far the most effective app was Juice Defender Ultimate,
https://forums.androidcentral.com/e...id=com.latedroid.ultimatejuice&token=nPmXtUoK. You can use one of the preset modes, which work great, or tweak it as much as you would like, it can get pretty detailed. It's basically as simple or as intricate as you want or need. I have also found in the past that using Tasker, and setting up various tasks to automatically turn off things such as GPS, WIFI, etc., when not needed, and have a task turn them on only when opening apps requiring them, can really help. Overall, I would say Juice Defender, by far is the most effective, being capable of slowing CPU speed, along with many other controls of the various radios, etc., it can really meet individual needs. If tweaked properly, I have seen it increase battery life by as much as 50 %.