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Wednesday, 29 July 2009

Getting to grips with electric cars

This looks interesting at first blush, but is it any more than a typical undrgraduate engineering project, albeit that they have a budget the size of a house and a power supply from the on campus ower station at MIT?

Mind you i like the idea that they are getting to grips with high speed charging, although the idea looks quite daunting if we assume that the typical running time between charges is 5 hours then the bateries would have to charge 30 times faster than they discharge. This is not too difficult for the batteries, although I suspect that it shortens the lives of lithium batteries considerably, but let us not be too concerned about that.

The problem is that if we assume the average output of a standard car is around 40kW when running, it would take a 1.2MW supply to charge the battery in 10 minutes. At 240V that would be 5,000 amps, which would be an extraordinary cable. More likely would be 2,400V at 500 amps, but that is not the sort of voltage you would want to be handling, particularly at a petrol filling station. I don't have that sort of power on my domestic supply, and it would be quite a transformer. to get that to work.

Still if they can get it to work they would have my vote. Not for any green issues but because electric cars can be very fast and light, and because the day of the petrol car is largely over. If there is one thing that annoys me about cars, it is not the emissions, but the simple fact that a $90,000 Porsche only costs $22,000 to build, the rest is overheads and marketing. So give me a Tesla or a Wrightspeed X1 any day. Simple cars cost less and go faster.

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