I put the red cable on the large post on battery and then attached the black to the metal on the car frame. When I turn on the charger the arrow points to the word "charge" at the very left side. As you move to the right is % 100 down to 0. I am not sure why if I have a dead battery the arrow does not point to 0. I am afraid to charge the battery since i do not know if it is correct. Please Help!