My battery died last month for some unexpected reason. I got a Diehard Gold free of charge under warranty. I'm still wondering why it died. I think my alternator is fine and I didn't leave anything on overnight. Could there be something else that is draining the battery? I also have a voltage meter in my car and i noticed that the voltage fluctuates between 15V to 12.3V while the car is running. It gets to 15V sometimes when I just start the car on a hot day. It then gradually goes down to and stays around 14.2 to 14.5V during the daytime. At night when i have the lights on it around 13.9 and 14.1. WHen i have he A/C on with the lights on, it can drop down to 12.5 when i'm stopped at a light with the turn signal on.. Would this be an indicator of a bad alternator or is this normal?? I did rewire my corners to stay bright and rewired my blinkers to alternate flashing with the sidemarker bulb next to the corner. Would this cause too much of a load on the alternator? I also have a 300 watt amp running 8 guage power wire with a 1.0 farad cap. I usually don't bump too hard but occasionally do. So what is the normal voltage while running under my conditions?