What Is Android Kernel
Basically, your Android device is shipped with a stock Android kernel and the key responsibility of your Android kernel is to connect Android apps with relevant hardware parts. The key functions of your kernel manage the battery usage and the kernel decides the battery life your device. The stock kernel has been designed by your device manufacturer to provide safe and stable battery power which is enough to maintain the good health of your Android device although the device is switched off. The kernel does not change the battery power according to the device performance as frequent changes may harmful for the device. Although the mechanism protects your device, it wastes lots of battery power in the vein and also this mechanism becomes an interruption when you a game that needs more power to process. That is why custom kernel become more valuable to adjust kernel settings as you want
How To Install Custom Kernel On Your Android Device
There are two methods to install a custom kernel on your Android device. You can install the Kernel manager app on your device and download the relevant kernel on your device. This is a simple method but you need a rooted device to perform the mechanism. Technically, you cant use this method on every Android device as kernel manager apps do not support all the Android devices.Either you can flash the relevant kernel file in a TWRP recovery method without rooting your device. But, you have to root your device after flashing the kernel since you cannot install a custom kernel manager on your device to adjust kernels setting without root access.
EX Kernel Manager
EX Kernel Manager is developed by Aaron, aka flar2 who develops the ElementalX custom kernel. The app is compatible with Samsung Galaxy S9/9+, Xiaomi Redmi Note 3, Nexus 5/6/5x/6P/7/9, HTC U11, Pixel 3/3a/2/ and few other devices. You can check the compatibility of your Android device with EX Kernel Manager here.
Final Word
Make sure to get a complete back up of your Android before the move. It is advisable to get Nandroid backup and move it to your PC before dealing with any stock feature. Also, make sure not to reduce battery power to the least amount as it may cause a boot loop since your device is not getting enough power to boot.