Battery is dead in the stang and I am borrowing a neighbors charger.... Now this thing has to be 20-25 yrs old and has two settings... 2amp and 6 amp. It seems lie it will take many many hours to get this 1000cca battery to turn over the 5.0 but my main question is do you think its safe to leave it on overnight? I am not sure if this dinosaur thing has a n auto shut off.