I'm not to sure on trasporting, but I know there are rules for storing large amounts of batteries. Where I work someone from the EPA did an inspection and one of the owners had his boat battery sitting on the floor and they told him he had to move it into a sealed container.
Sulfuric acid (battery acid) is corrosive, so state DOT might require placards and/or a hazmat endorsement if transporting more than a certain volume. I imagine it would take a lot of batteries for that to become an issue, as most of the weight in a car battery is the lead, not the acid.
OK, thanx. I have taken 3 at a time, but this may be as much as 2 dozen and I don't need any fines. My route requires me to travel out of state then back into my state. I guess I'll call both states to see if there are any special laws or licences required.