Its a 100amp alter. and the battery is a red top optima, which is only about two years old and I have an electric fan hooked up to the negative cable, its a 75 impala. But the battery isn't holding a charge overnight and i don't know whether we jumped it off to many times and killed the battery, or is it grouded wrong and thats why it won't hold a charge. Had no problems until he took this engine out and swapped it in this car. only thing different is i put an elec. fan in this car.