usb cable charging problems

so i have two usb cables and original. 2.0 amp samsung wall charger, the samsung cable i use for wall charger at home so when i setup my s3 as a AP i need constant 2.0 amp from charger keep up with the demand and charge the battery at same time but now i cant do that i have turn off hotpot and leave the phone alone so i can charge. i brought in my car usb cable, and now i can hotpot and charge at the same time no problem, so what is the problem with other cable? i mean cable still works and i still can use it for data transfer etc...
just cant use as heavy demand cable.