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EV Noble Rev2
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Written on: 16 April 2010 [23:49]
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rkdjones
Topic creator
registered since: 25.02.2010
Posts: 3
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An electric car came to my attention recently that looks like it might have some unique features. Revolution cars sells EV Noble Rev2. It's a Smartcar look-alike: 72V, 2500lbs, 8.5KW, lead-acid batteries with lithium option. My local electric car dealer said he saw one but wasn't impressed with the fit and finish. That said, the thing that appeals to me is the 5 speed manual transmission. Most electrics don't have transmissions and I've wondered why. I've test driven a number of electrics in hilly Seattle and their performance on hills in not impressive. (My 500W electric bike has an 8 speed transmission that allows me to climb hills; without it I would be topping out at 8 mph or stalling on hills). My understanding of electric motors is that they have an efficiency band near their free-run speed. Though they can generate a lot of torque at low rpms their efficiency drops off. If a car without a transmission manages to climb hills the range suffers because the motor is operating at very low efficiency. So I throw out two questions: - Has anyone seen and driven a Noble Rev2? - Am I missing something about the technology with my understanding about efficiency as a function of RPM. Robert |
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Written on: 20 April 2010 [19:03]
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ecoadmin
Administrator
registered since: 20.07.2007
Posts: 583
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Hi Robert, Here is a graph which might explain it a bit:  The chart shows max torque at 0 rpm i.e. when the motor is stalled; Max power is at 50% of peak rpm; Maximum efficiency at approximately 75% of peak rpm – 90% for a good brushless I am no expert on this, but it looks like your statement is confirmed by the graph. Anyone else with more insight on electric motors and their efficiency at low rpms? ...and no, I haven't seen a Noble Rev2 yet. Twike 890
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