Once upon a time, in the nuclear submarine navy, my shipmate tags out the ship&#x27;s battery breaker.  As part of the tagout, he checks that the ship&#x27;s DC bus is deenergized - within the battery breaker box itself.  During the check, he finds some voltage, which isn&#x27;t entirely unexpected, since there is enough capacitance on the DC bus to hold it charged for a while.  So he uses a specialized grounding probe - about 1&#x2F;8&quot; diameter copper rod with a reinforced handle - to discharge it.  Unfortunately, he has misunderstood what was inside the breaker box and is actually shorting out the ship&#x27;s main battery!  This is a couple hundred volts DC, and a few thousand amp-hours of capacity, and it delivers enough current to instantly vaporized the grounding rod.  He&#x27;s knocked on his ass by the arc blast.  Fortunately, he was correctly considering the box to be energized gear and was wearing a full set of PPE, suffering only minor flash damage to his eyes.