Well lipo's or Lithium Polymers, are the going craze of batteries. They offer a very lightweight power source for the comparative nicad. With the lighter weight you can get a larger or more capacity battery. While your nicads is 1.2v per cell, one lipo cell is 3.7V. So for sake of example a 6 cell nicad pack makes 7.2V, and only takes 2 cells of lipo to get the same voltage.