What causes a tablet to take 10 hrs to charge full?

Nexus 9
I don't have original charger (that is 1.5A), but instead use another tablet charger that is 2A...
Have tried several chargers
Obv: airplane mode, bluetooth, location wifi off, everything off, every app turned off
Update: SOLUTION: nokia charger cable is the only one that charges speedily...
with other cables (that work fine with other devices delivering 2A) I'd only get percent or two per 10 mins, with nokia charger cable, I got at least 3, maybe even more
4 answers 4