Electric cars are great, but battery technology continues to be holding them back from mainstream acceptance, the limiting factors being battery capacity and cost. Many companies are working on this problem, and Envia Systems recently announced they’ve achieved an energy density of 400Wh/kg, roughly 2-3X the energy capacity per unit of weight as current batteries on that market and at a lower cost. You can expect to see this on the market around 2015, with the result being 300-mile range electric cars for maybe as little as $20k. Read more over at gigaom.