As I said in my post #8, the probable cause was a momentary drop in the input voltage causing more current to be drawn to maintain the same power level. There was a firmware update (3.5.17) in May, 2010 to improve the timing loop of the charge algorithm to prevent that behavior. Is it possible that the firmware in your car has not been updated since then? Seems unlikely. I would not expect fuses to fail due to age, though.