I have no idea how heavy any of the various nuclear batteries are. No i'm not talking of a nuclear reactor. Go to the wikipedia entry on "atomic battery". One variant is described by wikipedia as "the weight to power ratio is said to be comparable to an air-breathing engine with fuel tanks". There are bound to be other disadvantages like cost, liscencing, and safety (radioactive spill during crashes). But lets forget those for the moment.
My idea involves modifying an electric car. It might also work with a serial hybrid car. For the serial hybrid all you need to do is to remove the gasoline motor and plug the nuclear battery into the charging circuit. If you use a small nuclear battery the amount of current will never be enough to drive the car so it trickle charges the batteries. This would be ideal for a commuter car. You drive a short distance and when you arrive the battery is nearly empty. You park the car and go to work. When you get off at 5pm, the battery is full.
At night and on weekends, you can keep the car connected to your (specially modified) house so after the car's battery is full, extra current helps decrease the rate at which your home electricity meter spins.-- vmaldia, Nov 01 2008 Wikipedia: Atomic Battery http://en.wikipedia...wiki/Atomic_battery [theGem, Nov 01 2008] HB: Atomic BatteryOddly enough, this link is inspired by [UnaBubba] [theGem, Nov 01 2008] ...too lazy to look it up, but aren't the output of those batteries (used in deep-space probes) seriously small ? like watts, not kilowatts.-- FlyingToaster, Nov 01 2008 random, halfbakery