Here is the link ==> http://www.forbesautos.com/news/features/2...in-hybrids.html This article addresses plug-ins and highlights EnergyCS modifications of the Prius. Apparently they now use a Valence technology battery (Lithium Ion) that is 231 lbs. to replace the 77 lb. Prius battery, with the replacement now fitting in the luggage compartment where the spare tire now resides. Apparently, this battery helps achieve a 130 mpg mileage rating by helping the Prius go for about 30 miles on electricity alone in city driving.
