Moto E 2015 battery life is pretty good but it is not enough for power users. Phone experts say that one of the best ways to increase Moto E 2015 battery life is by flashing a custom kernel. The one that we recommend flashing is Squid Kernel and it is based on original stock kernel. Features of Moto E 2015 custom kernel:
[ ] Moderately under volted
[ ] Permissive SE Linux
[ ] Updated to Kernel 3.10.73
[ ] Synced with latest Code Aurora changes
[ ] Simplified build process
[ ] Compiled with Linaro GCC 4.9.3 and optimized for Cortex A53
And in case you would like to revert back to stock kernel, all you have to do is download and flash stock kernel from here. This file is a TWRP flash able zip of the stock kernel for the Moto E LTE. You should have bootloader unlocked on Moto E 2015 before you flash any kernel, including stock kernel.
Keep in mind that this kernel is only meant to be flashed on Moto E 2015 LTE version that is on sale only in selected countries. Another known issue is that this custom kernel would not work with CDMA networks. A test kernel has been released which makes it work with Boost Mobile though. Also this kernel sometimes hangs or reboots during the boot process.
This is probably due to a race condition. Be patient, and give it up to 2 minutes to boot before giving up. If it fails to boot the first time, it should work after the first or second reboot.