btw, i use reverse tethering on my phone and have my relay running (still testing but working pretty stable and reliable now) so my phone is always plugged in... and because android still doesn't have proper charging controls, i have to root it so i can set it to limit the charging to 80% so it doesn't blow up the battery running on cable all the time... you will discover this as you progress on your re-wiring journey with mobile devices

of course if your phone is running graphene you can probably actually get root and control the charge system to do this, but for other devices you can't reflash the rom rooting is the way