Arcing when connecting the controler

[genesis11]

New to the forum, it's a great site with excellent resources! I recently purchased a used 06 EZGO PDS with factory drive components, a lift, & 22" tires. After driving it on mild terrain it quit. I found one of the batter terminals melted were the lug attaches. Found a thread on how to drill & tap it and have done so. when I went to connect the negative side of the controller back to the batteries it arced. This all happened right before I had to come to work on midnight shift. So I am sitting here going nuts wondering what is wrong. I have done not further testing because I had to leave for work. Just wondering what direction I should take first. Any help would be greatly appreciated.
Thanks--Once again, a great site!