People commenting that their kobo was fully charged in 30mins, or whatever, are incorrect. The light will shut off and indicate fully charged, however, this is just not the case.
If the manufacturer recommends three hours to charge, that is the minimum you should leave it for. You can leave it charging all night without worry of damaging it.
If you do not let a battery fully charge, it will deplete much quicker. That's the same for pretty much any devices I have used and I have lots.
Ignore the red light, whether it works or not, and let it charge all night. If you still have issues with fast discharge then it should be returned as defective.