Hello! I got my S4 the other day and it seems that my power adapter is having a glitch, because i can play with the S4 via USB but as soon i plug in the power adapter the LEDs turn to 100% for like 0,5 seconds and then they return back to 50% as if they were powered by only the USB. And then they can like randomly change back to 100% for like a minute and then turn down to 50% again.
Did you check the preferences, under kontrol s4, there is an LED section, on state and off state section, make sure the on state is at 100%. Otherwise faulty power cable.