My cheap 4k MaH bank connected with 1.0 output can charge 20% (not intense using it). Ur bank will drain fast if ur using ur tablet especially the screen it needs alot of power so it feels like it doesnt charge at all. But beside that my bank saved me a couple times.
Had to add that peter is right……you need a 2.0 A output (no between split cables, no longer ones, these all cut into ur power traffic) even a wall powered between splitter of 8 feet connected will drain battery when using performances likes muktitasking and graphical handlings. I confirm that you can game fullpotential on steam whatever while having the original cable plugged on a 2.0 output.