Was just talking with an old time battery guy who said some batteries they had trouble with had what they called a "hole" in it, where no matter what you did it would not go above 13.5 volts, eg. It would heat up real good if you kept trying though. I think he said sometimes they would jolt it past there with an 18 volt shot.
He said some had a "gap" instead of a "hole." These would work fine with a 20amp draw but not be able to run a light bulb. It needed something big to jump the gap and then work ok. I think he said after they jumped the gap then they could reduce the draw and it would then run a light bulb. He had lots of stories as old-timers do. :)
