Yeah I'm pretty confused myself. The phone will charge when it's turned off. For instance I'll plug it in at night with it say %15 left till the battery is dead, go to bed, wake up and the phone will be off and when I turn it on it will be fully charged. All of that meaning that it died while on charger and then charged while it was off. Plus after noticing that, I tried charging it with the phone off and it charged.
Same with car chargers.
I'm stock rooted. All I needed and wanted from root was WiFi tether.
I've tried every charger possible, lol.