Battery becoming very hot

Mattax- Thank you for all your assistance. Been working alot and just got home and began working on the Dart. Please see below blue wire goes to alternatorIMG_20181103_170518.jpgBlack wire has a fusable link and goes to starter relay IMG_20181103_170456.jpgstarter relayIMG_20181103_162749.jpgIt might be like you said the other black wire on the red stud on the ammeter. I do not know where that one goes.
Also do you know what the plug in the picture belongs to? Found it as I was looking at the wires. IMG_20181103_165359.jpg