[GTP Dad]

If the alternator will run the vehicle when the battery is dead then the alternator is good. An alternator only maintains a battery and if the battery is not recharging itself then it needs changed. A battery continually recharges itself through a chemical reaction. If that reaction does not work properly then it needs replaced. I suggest you change the battery with a new one.

Also check for a corroded connections at the battery and the alternator and check to see if there is a short by checking for current flow when everything is shut off. You may have a glove box light or trunk light that is staying on and draining the battery.