Need Help With Electrical Diagnosis

Make/Model: 2000 Jeep Grand Cherokee Laredo,
4.0l, 208,000 miles

Problem started yesterday. On dash the light
saying "check gauges" came on. I looked and my
battery gauge was all the way down, like when the
car is off. Moments later it was back up and the
check gauges light was off. It went on and off on
my way home, beeping all the way each time the
light came on. No change in the way it ran
Today, while heading to auto parts store it was
doing it again, and more gauges were going out
and would come back. Eventually the key light and
seatbelt light was on too.
The alternator is working great, and the computer
scan only came back for the key chip (I'm using the
original keys though)
What could be the problem?