How to fix my Charger with battery light on?

I would have researched the battery and alt BOTH before just pitching em out. Test alt while the car is running and you should be looking at about 14.2 to .7 going into the battery. When testing the battery, you don't want to see it at 12 or just under. Did you pop the toff off and see how much acid was in the cell(s)? you wont get proper CCA if you are low on the acid. When you test the battery you will be fine at 13.2 to .4

Have the alternator tested out of the vehicle. It's not unheard of to get a defective one right out of the box. Or the new battery might be defective, but that's less likely. Hope that helps! Jim

Almost always when customers come in with battery light on, it is the alternator. And usually the bad alternator made the battery bad. I always suggest changing both even if battery was a newer dated battery. Why? Because when a battery goes below 10 volts, it is deemed unreliable from that point on and has dead cell issues because of driving just on the battery power alone. And yes like another guru said, you can get a bad alternator out of the box. Also make sure you have the correct alternator for your model vehicle. Some models have 2 different possibility alternators because of options. Also stick with OEM models they were designed to work with your car. Mopar in your case.