Hello Klue, 

Keeping a charge on my phone is something I pay close attention to, as I know how important it is. I can definitely assist you with power saving ideas. Here is a link that is specific to the s8: http://spr.ly/6606EoyEM

In addition, I have included a video that helps with all Android devices: http://spr.ly/6607EoyE3 

I also want to recommend a power bank, so you can make sure you have a charge, even when you're on the go. Check out these options: http://spr.ly/6608EoyEO* 

ChristinaB_VZW