Over reved alternator?

No idea. Pull it off pull it apart and inspect it. "Back in the day" I blew up a couple of alternators. One day I got to thinkin, rare for me. I measured the pulley dia on the (then) 440-6 RR and it's a 4:1 reduction. This means that if the engine is spinning 5K, the alternator is going TWENTY THOUSAND.

However, the voltage regulator should "cut back" the voltage regardless of RPM, so unless something is just plain wrong, like a bad regulator, etc, the battery should not see a problem