Kurt, Sounds like you got ahold of a bad alternator. More precisely a bad regulator in the alternator. Mine did the same thing on the way back from BG last year Labor Day weekend. Gauge would peg out to the high side and then would suddenly drop to a hard discharge condition and cause the car to stall and cut-out briefly, then go back to high charge. After two weeks of testing and retesting, my local starter/alternator repair shop figured it out. The regulator wouldn't get hot enough just driving around town on short trips, but on the longer trips on the highway it was getting way to hot and causing the problem. Had them put in a new regulator and no more problem. Also had them up-grade the alternator to a 105 amp at the same time. Cost me about $75.00 bucks. Well worth it. If I were you I wold try a different alternator or have the old of tested by a reliable shop. Zane
What Zane said is correct. Your voltage regulator on your alternator is not working. Replace your alternator or have the regulator changed as soon as possible. Overcharging your battery at the rate you describe is very dangerous as an overheated battery emits sulfuric acid fumes which are not only very corrosive and harmful to your health, but EXPLOSIVE. You also risk burning up other electronic equipment such as your computer with voltage that high.