Hooking up battery charger on Model A

[Afordman31]

My Dad asked me tonite how I hook up a battery charger on my Model A with 6 volt positive ground. I said like any battery, red to positive post and black to the negative. He asked if the battery was out of the car what then, I said red to positive post and black to the negative post.
He said on his Model T's he hooks up the red lead to negative post and black to the positive post.
Are we both doing it right? Afordman31