Out of the blue I went to start my car and the battery was dead. I charged it, then my wife and I took it out shopping and to dinner and everything seemed fine. This morning I went out to start the car and once again the battery was dead. Both times I had made sure nothing was left on and after charging the battery again, I put it in to make sure there was not light that was staying on by itself etc.. Any suggestions on what will drain the battery over night?