(KL)GOLDEN, CO--Principal Engineer, Center for Transportation Technologies and Systems, Ahmad Pesaran, Ph.D., holds two vehicle batteries, a nickel metal hydride battery, left, used in the current Toyota Prius Hybrid, and a smaller Lithium-Ion battery tha

(KL)GOLDEN, CO--Principal Engineer, Center for Transportation Technologies and Systems, Ahmad Pesaran, Ph.D., holds two vehicle batteries, a nickel metal hydride battery, left, used in the current Toyota Prius Hybrid, and a smaller Lithium-Ion battery that he and NREL are developing for future cars at the National Renewable Energy Lab, NREL, in Golden Wednesday morning. Andy Cross/The Denver Post (Photo By Andy Cross/The Denver Post via Getty Images)