[Xiaomi Redmi 3s ROMs, Kernels, Recoveries, & Other] SuvamLP4549:
My TIPS, non-root and no 3rd party app required.

*Keep your location permission off as much as possible. I mean use only when required using that quick toggle on the QS tile. And then grant that permission only to the apps you really need. Check the permission list and you will find many apps having that permission for absolutely no reason and that counts! I found that the Google app's gonna drain a lot with location on. So I turned off for it as well as the play services! Your preference might vary!

*Totally disable the Google Location History for all the Google accounts you have logged in to on your Android. What it does is that it keeps record of your location from time to time in background which results in drain!

*Okay Google hotword from ANY SCREEN in the Google app DISABLED! Well, I think I needn't describe. Just keeping it on results in a significant battery drain!

*Background sync totally turned off. That quick QS tile for sync is not available in this ROm yet. Don't know why! But that doesn't mean you keep that Auto-sync on. Who needs to refresh every hour! I totally disable to Auto-sync of Google apps. You can see there as well that turning it off saves battery, mate!

*System animation down to 0.5 for all three options out there in Developer options. Not only this speeds up the whole thing, but also ensures more juice at the cost of less animations! ??

*Keep your eyes on Bluetooth and WiFi toggles. Ensure that they are OFF WHEN YOU DON'T NEED THEM. SAME WITH DATA AS WELL!

*Ensure that WiFi and Bluetooth scanning are turned OFF in the location settings. They will just eat away the battery life.

*Under display, turn off the screen saver. You'll never need it!

*Turn off Ambiant display there as well! We don't have Amoled display on our Land. So it drains our battery! Simple as that.

*If possible (I am okay with this) turn off Adaptive brightness when you are at home or don't need it to get charged frequently. There is an option to add a quick toggle right next to the brightness bar in the notification shade. I never turn on the adaptive-brightness. It sure helps save some juice as well!

*Controlling your display brightness manually will really help bro. Just keep it at the bare minimum yet comfortable. In evening, I perfectly fine with brightness level of 7%. Why bother turning on Adaptive-brightness?

*Night light. Just set time or leave it as is. Use the QS tile toggle it on or off when required! Choosing sunset to sunrise needs your location and you know what I am referring to next!?

*Screen Orientation. Yup, keep this in check. Never turn on auto-rotate. You don't even need to! What it does that it keeps using sensor to know the device orientation, thus using more battery! You cannot always toggle it on there. But don't keep it on when you don't need!

*Disable or uninstall the apps you don't use! And which apps keep eating your battery on background (i.e Facebook, Instagram, Twitter etc), deny them from doing so on the application settings. Toggling off their background usage will enforce them to just do the bare minimum instead of just killing battery adruptly! Do the same with App Data Usage option as well! Deny them from using data in background. You can always open the app to use.

*Turn off notifications for the apps you don't need to show up! Accept this. There are many apps on your land, whose notification don't really matter to you! That saves you battery.

*Turn of vibrations everywhere! I have turned off keyboard vibrations. Navigation button vibrations. And have turned off vibrations for the notification of any app. Be it any app, I don't need my land to vibrate for a notification! It sure saves the juice.

*Turn off weather on Lock screen if you have it turned on. You know why? It needs your location! ?

*Finally, blocking ads sure saves your data, time and battery. Try AdGuard once you will be amazed!

For YouTube video ads, use this mod-

*YouTube iYTBP mod with MicroG-

https://drive.google.com/drive/mobile/folders/1RNk38edZgHvNlJ5TN3jkSImox4BJOC2P?usp=sharingno

Uninstall the official YouTube first. You will never need that again! ?

Then install the modded YouTube, don't open it yet Install MicroG. Then open the modded YouTube and login n enjoy!

That's all bro! Never thought that this list was gonna this big. But I just kept writing! ? Love to help others. Please do all I have told above and the results will be there. One more thing, I've not rooted my phone. I've the 2 GB variant so on rooting, I run out of RAM and the system crawls down! ? I don't use Greenify. Doze on Oreo is more than good to make me forget that app. Absolute zero drain on sleep! I love Oreo.