[Lobo1186]

I am having some difficulty trouble shooting some battery issues. I was driving the other day (about 210mi) and the battery light came one. Generally this means the alternator is no longer charging the battery. Unfortunately for me, I was about 120 miles from home. So I went to walmart which happened to be at the exit I broke down near. I bought a new battery and a charger. I was able to finish my trip and I put both batterys on the charger. Once I started home I was able to drive the whole trip before the battery died near the gate to my home. I put the other battery in... now seemingly for no reason the battery light is off all accessories run fine. Any clues as to the problem aside from a dying alternator?