One of our shop trucks had a dead battery. The warehouse guys were trying to hook up the cables for the charger and couldn't get the negative lead to stay clamped. So I told them it can just go to the chassis, it doesn't need to go to the post. Walked out of the office later and I hear the charger buzzing pretty angrily. They had the positive on the alternator and the negative lead on the positive post. I don't know how they extrapolated what I said to mean that