The biggest disadvantages of electric vehicles are prolonged charging times, high cost of lithium batteries, and mass of the batteries. Even though (according to my own calculations) lithium batteries are about 4 times more energy dense than their lead acid counterparts, the mass of lithium battery material needed for a road trip can be 10 times that of the gasoline that can be used to cover the same distance in a conventional vehicle. In contrast to internal combustion engines and fuel cells which use the atmosphere as the means for obtaining oxygen and releasing carbon dioxide and/or water vapor, batteries must contain all of the ingredients of the chemical reaction that provides the electromotive force. This adds up to tons of added mass if you need to move a one ton vehicle over a hundred miles. All of this might be overcome by using supercapacitors instead of batteries. A capacitor is a device capable of separating and storing positive and negative charges. Depending on the source of current, capacitors can be charged almost instantly. They are currently used in defibrillation devices in order to provide short bursts of intense current. Supercapacitors made from graphene (an allotrope of carbon) are able to store unusually high levels of separated charges. Lithium batteries are expensive because (in contrast to carbon) lithium is rare and there will never be enough to provide electric vehicles worldwide. Another disadvantage of all rechargeable batteries is their loss of charging capacity over time. This can be attributed to the accumulation of undesirable by-products from side reactions that take place during repeated charging and discharging. Since capacitors do not involve chemical reactions, loss of charging capacity over time is much less of a problem. Although to my knowledge this new product has yet to be used for electric vehicles, the idea is out there and I will be on the lookout for new developments.