Many people use the term "battery" to describe anything that gives off power that can be used for another purpose. The average consumer is totally used to the idea of a AA-sized alkaline battery that comes from the store charged, gets used up and then gets thrown away. So, the idea of a "battery" which could potentially last... say, 30 years sounds awesome! And indeed, the technology exists already in the form of the power source used in some space satellites. Via the decay of Tritium, researchers are working on a power source which would act like a battery that lasts a very long time. Think of the process like weak nuclear power. The type of radioactivity that the power units give off can be easily blocked so that it is not harmful to humans. Of course, there are drawbacks. The unit is rather heavy for the power it gives off and is too easily damaged to be used by consumers. The military, however, might be interested. So, while we might not be driving electric cars that generate their own on-board electricity from decaying radioactive matter in 5 years, in 50 years... who knows?