By ca95dream , March 21, in PD24 Forum. I have been running my car Plymouth Cranbrook for over a year now with the negative terminal grounded to the engine block. That is how the car came when I bought it. The battery is very old and does not hold enough of a charge any more and so I decided to replace it. I bought an Exide 6 volt. When I bought the battery, I was reminded that the car is a positive ground.