Thanks everyone for your suggestions! I bent the main battery wire up and taped it, like Cougar suggested, and now when I hook up the battery, no sparks! However, when I try to start the car (the proper way), I get absolutely nothing. I checked the battery charge level, and it was a little low, but not quite low enough for completely nothing to happen. I’m gonna double check all the other connections, working on fixing the insulation and getting new cables as well.