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User Info	What IS This Nonsense? (Electric Cars); entered at 2011-05-16 13:35:20
2b\|!2b:? Posts: 102 Registered: 2009-05-22 Unraveling Scams of America	Ok, I feel I need to chime in on a couple of things. First, make up your minds regarding home vs. "charging station". The hand-wringing about typical house wiring not being able to cope with a QUICK charge, are nonsense. Nobody is going to NEED a QUICK charge at home. The QUICK charge is needed when you're on the road, and need to pull into a SPECIALIZED station, recharge, and continue on your way. At HOME, you're going to trickle-charge (probably overnight). Moreover, your employer eventually might have trickle-charging stations in your parking lot, so your car could get topped off while you spend those 8-9 hours a day at the office. Next, energy density. Yes, gasoline has much higher density, but as Genesis recently pointed out, internal combustion engines have horribly low efficiencies compared to electric motors. Using 12.3 KWh/kg for gasoline (per Wikipedia), at 25% efficiency it's 3 KWh/kg. For the electric equivalent, let's ignore charging losses (since they don't impact the car itself -- only the overall cost of "fuel" per quantity of miles driven), and assume 10% discharge loss (heat), and 80% efficient motor. That's 72% overall efficiency for the engine, nearly 3x the maximum for a state of the art gasoline engine. To achieve parity with gasoline, the battery would need an energy density of ~3/.72 = 4.2 KWh/kg. Which is roughly 3x the current state of the art... However let's not forget that the IC engines are huge and heavy in themselves (not just the engine block, but also all the cooling and exhaust management systems surrounding it.) The transmission system for an electric car can be much simpler and lighter as well, since most electric motors can naturally provide reasonably consistent torque over a wide range of RPM: to the point that there are even proposals to put a small electric motor directly into each of a car's wheels. Overall, an electric power train is much more compact and much lighter, making the overall car more compact and lighter, which means you need a lot less energy to move it compared to an IC car. AND, having an electric motor on the axle allows you to naturally use it as a generator when coasting downhill or braking, which lets you recover power that would be wasted by an IC car (this is what all the hybrids do already.) All of which means you can get away with hauling a heavier/larger battery pack holding less overall energy and still achieve overall form-factor and performance similar to the gasoline-powered car. So in fact you don't need full energy density parity in the first place. And if you're willing to compromise on the range (e.g. go down to 200 miles vs. 400 miles between "fill-ups"), altogether the concept makes sense -- even with TODAY's technology. It'll only get better as technology continues to improve. 2011-05-16 13:35:20