Though hybrid cars take in substantially less petroleum than conventional cars, there is still an issue regarding the environmental damage of the Hybrid car battery. Today most Hybrid car batteries are one of two types: (1) nickel metal hydride, or (2) lithium ion; both are regarded as more environmentally friendly than lead-based batteries (which constitute the bulk of car batteries today). "Jim Kliesch, author of the 'Green Book: The Environmental Guide to Cars and Trucks' told, 'There are many types of batteries. Some are far more toxic than others.