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IF YOU want to buy an electric car, you can. Tesla Motors, a firm based in San Carlos, California, will sell you a nifty open-top sports job for $109,000. Not cheap, admittedly, but cheap to run. Plugged in overnight, it can be refuelled for the equivalent of 25 cents a litre of petrol. The catch is, “plugged in overnight”. Tesla’s vehicles use standard lithium-ion battery cells. As any owner of a mobile phone or laptop computer knows, these take time to charge. If you use 6,831 of them, as a Tesla sports car does, that time does tend to drag on. Which is fine if you are not planning a long trip the following day, for a full charge will take you about 350km (220 miles). But it might cramp the style of anyone planning to bomb down from, say, Paris to Cannes, and who would therefore need to refuel on the way.