Battery not charging

There is something in the car that is drawing electrical current even when the car is off. To find it, first investigate simple things like courtesy lights that stay on (also trunk/cargo area lights and glove box/console lights). If you don't find it, connect a meter in line between the positive battery cable and the battery post. If it reads an amperage draw, start pulling fuses until you find the one that is allowing the draw. That will tell you what circuit is causing the problem. Then go to the suspected devices on that circuit until you find the culprit.

You might have a weak battery or bad new alternator. Take it to ur local auto parts store, they will check the charging system for you free of charge

If battery is indeed good, as discussed above, need a parasitic draw test done IF it's draining while sitting (not running). If it's dying on you while running, need a ripple test done, new alt could have bad diodes right out of the box. I went through 3 new alts before I found a good one recently on my own TB.