I finally took it out for a test drive. I first let it sit in idle for about 10 min. No stall. I then took it out for a short test drive. No stall. I let it sit in idle for a few more minutes and took it out for a longer test drive. This time, just as I was making a turn it stalled. All my warning lights came on at once, with a flash, and then the whole car abruptly died. I tried to start it again, but had no power.
I saw the same thing a couple of years ago when my alternator went bad. I put a lot of miles in the car, roughly 500 a week. I probably could look up how to test the alternator, but I don't have any equipment for that. Any suggestions?