Electric cars lose as much as half of their value after just three years on the road, new figures show, as the rate of depreciation far outstrips conventional equivalents.Research from Auto Trader said there were “unsustainable levels of depreciation” in the electric car market, with used prices of battery-powered vehicles dropping by 23pc in the last year alone.The online vehicle marketplace said a motorist buying a £50,000 electric car could expect to lose £24,000 in value over three years, wh...