hello eveyone. i have a scenario going on. I noticed that as i am driving, for instance, if i accelerate the volt guage will rise. if i let off it will drop down to 12 volts. now what gets me is when i do accelerate, it will rise all the way to 18 volts. i have never seen taht before. yesterday i went to start my car and it would start up. tried juming it and it wouldnt. (battery was completely dead) changed battery and jumped it and it started. but when i turned it off for about 2 minutes and tried it again, it had already drained the battery down to mid point on the volt guage and barely turned over. the last attempt would not even turn the motor over. does that sound like the alternator?