An F30 BMW 328i equipped with the N20 engine was displaying an IDrive warning of “Charging malfunction: Battery is not charging. Stop Carefully. Consult your nearest service center. What’s responsible for charging the battery is the alternator, so it was easy diagnosing what the issue was. When doing this procedure it’s best if you go ahead and replace the following items along with the alternator.
One thing to note is that there are two versions of the alternator. A 170 Amp, and 210 Amp variant. For this particular car, it was the 210 Amp variant. You can tell which one you have by looking at the label on the side of the alternator, and it will state 170 or 210.