Everything seemed to be working normally anyway, continued for another 20 miles or so. With the car safely in the garage, shut off the engine and restarted and the light went out normally after the bulb test. The battery is 5 years old and the car has 150K+ miles. Most likely Alternator problem? Will that diagnose at a shop even if the idiot light is off?
'Battery' idiot light came on on 2000 Plymouth Breeze
The light comes on when the battery is discharging or the alternator is not charging. Even if the light went out a diagnosis of the charging system is possible. The unit will determine if the alternator has any output and if the battery can pass a load test. Good thing you caught it now but before you go anywhere else check the battery connections and make sure they are clean and tight. 50% of the problems start right there.