Monkey, granted, I don't know all the issues. What I said back then was it should be explored.
Maybe waste is equivalent, as you suggest, in which case it's a problem, but it seems one would need a product that quantifies how much would be required to run a car to determine whether nuclear waste from car batteries can be equated to the mountains of waste generated by power plants. My first thought was these batteries would last virtually forever, so it would be a smaller issue. And that they would figure out how to shield the stuff in autos such that it was safe and wouldn't end up being stolen for dirty bombs. Hmmm, they seemed to be known unknowns. 
p.s. ignorant question, why is there no explosion during decay?