On my old green Muff, the same thing happened years ago, and its still that way. I stripped off about 3/4" of the insulation and place the wire over the post and plug the battery in. It works, but isn't the best solution. I have a replacement plug, just have to put it on. A quick splice is all that's needed. Radio Shack has them as would most electronic shops. This was a common problem, I've owned three and each one did it. Be honest and either fix it or offer to, he should know that stuff can happen. Good luck!