You do realize that with a nuclear battery, if you were to, i dont know, get in a car wreck, you would explode and radiate/kill everything in the vicinity.
Sure they both carry risk, nuclear just carries way, way more. It would be impractical and dangerous. Besides, we have the tech now to make better more efficient batterys, and still have lithium which could be used. Problems is, those lead and acid batterys are about 100 bucks a piece. Everyone who owns a car will end up replacing them in a couple years spending more money, and thats really what its all about.
I feel ya, I always said i was born way to late to explore the world, and way to early to explore the universe. Sucks.
"Live as if you were to die tomorrow. Learn as if you were to live forever." -M. K. Gandhi