battery indicator light is coming on&current battery went dead. on 2004 GMC Yukon XL 1500

put in new battery & light is still on & alternator is new. truck runs rough too. any ideas?

Asked by for the 2004 GMC Yukon XL 1500
do you have pwr at large red wire in the rear of the alt. lets start there.
1 more answer
Need to have charging system tested. You either have some sort of wiring connection problem, defective alternator, or its possible the PCM could have failed. Alternator is controlled by the PCM.