About 2 weeks ago I was trying to get Dad's 55 Chrysler with 331 hemi running for storage. Found out I'd forgotten to disconnect the battery in the spring. Charged it a little and got it running only for it to die in the street while I was trying to turn it around. 12 jumped right from my minivan to the Chrysler and got it started back up. I don't believe it hurt anything! The dash lights were sure brighter for a min though.
I got it turned around and left the charger on it overnight. Started on its own the next day so nothing too wounded.