Battery light came on the other morning and went off after about 10 minutes of driving. But then it came on again at around 15 minute mark and flickered the rest of the way to work. I parked the car, turned engine off and measure the voltage across the battery and it showed 12.40 V, a bit low. So, I turned the engine on and measured voltage again: random fluctuation from 11.xx V to god knows where. Seems to me like bad diodes in the voltage regulator which I believe is at the rear end of the alternator.

It's a Volvo V70 1998 non-turbo, base model.

 

Given that you have no loose or corroded connections along the way, it does sound as if the regulator is giving up.

 

Time for new brushes