I've always tried to be careful keeping the bottom of the eroll from touching metal. Is this necessary? I'm not sure how it can charge through those contacts with the charger, but not be vulnerable to shorting. It sure would be easier not to worry about that. They have sometimes been left against metal momentarily, but not caused any shorting problem for me. I'd think there's probably some reason not to worry, though that doesn't comfort me much without knowing for sure.