While most plug-in hybrid and electric vehicle manufacturers are betting on innovations in lithium ion batteries to make their products more competitive, ZENN Motor Co. is placing a long shot on EEStor's ultracapacitors.

Unlike batteries that stores chemical energy, ultracapacitors store energy in an electric field. The advantages include lighter weight and faster recharge times than batteries, so a car with a range of 500 miles could be recharged in a matter of minutes.

EESTor has been quiet about its development and many folks are skeptical that they can build reliable products. However, astute VC firm Kleiner Perkins Caufield & Byers has given the company several million dollars, so they must have something substantial to offer.

If, and this is a big if, ultracapacitors can function as promised, they could make electric vehicles competitive in many applications.