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Old 09-12-2006, 06:33 PM   #11
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Here is an interesting read about traction batteries for an EV.

You may be over-engineering the motor / battery specs (a 50 hp motor may be more than needed in a car, muchless a trike). Usually the limiting factor is the current capacity of the controller itself.
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Old 09-13-2006, 07:35 AM   #12
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Yup, if the car were using an AC motor, 50hp may be the equivalent to a 150hp gasser because they rev to 10K+ rpm, but DC's only be able to equate to a gasser of roughly twice as much power because they don't rev as much as ACs. In any event, the torque would probably surprise most.

For the trike, I'd like to build something that's obscenely fast, but still is obscenely economical as well as affordable. The Tesla Roadster, just in stripped down microcar form. I doubt there would be much interest because it would be fairly spartan, but an ideal 12s quarter mile, ~1000mpg EPA combined energy equivalent, the ability to be powered by a single 100-200W solar panel, along with a sub $5k price tag for the DIY'er would be too cool.
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I think if i could get that type of FE i would have no problem driving a dildo shaped car.
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Old 09-13-2006, 08:54 AM   #13
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Something I found this morning . . .

http://www.evconvert.com/eve/the-battery-dilemma

— John Westlund May 10, 10:30 PM #

We had the better batteries 10 years ago. The Ovonic NiMH. 70 wh/kg specific capacity, 1,750 cycles to 100% depth of discharge. Robert Stemple, chairman of Energy Conversion Devices, quoted them at $150/kWh for a production run of 20,000 cars.

General Motors, not wishing to see the electric car go mainstream, sold the patent to Chevron Texaco. Chevron Texaco vigourously protects this battery and has sued Toyota for making a similar design. Further, with the oil company winning that case, it can now restrict the maximum AH size of the batteries to 10 AH. This prevents them from ever being used in a road EV, as it is not practical to go above 400V or so and NiMH cannot be charged in parallel with ease. Further, this oil company is responsible for about half of the price premiums on Today’s hybrids; they charge $1,200/kWh for the battery when it could be much cheaper!

At 70 wh/kg, a midsize car with attention to aerodynamics could have 200+ miles highway range with a 500 kg, 36 kWh pack costing $5,600 and lasting well in excess of 300,000 miles in theory. This battery has been denied to us. This battery would allow hobbyists to make 120-150 mile range conversions a norm, and 200-300 mile range conversions a possibility.
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Old 09-13-2006, 09:16 AM   #14
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To bypass getting the crap sued out of them, iirc electro energy is selling their NiMH design, which supposedly is similar but better than the ovonics design, to the US military/government at something like $500/kwh. Here it is. Some more.
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Old 09-16-2006, 05:03 PM   #15
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I was searching for something relatively unrelated and was pointed towards this article.

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Using parts that he had purchased for under $1,500, Dave designed and built an engine system for his Opel GT that could propel the car 75 miles or more on a single gallon of gas! Dave's Opel was a hybrid electric vehicle. That is, the car was driven by both an electric motor and a conventional internal combustion engine. An array of six-volt batteries provided the direct power for the electric drive, while an efficient six-horsepower (hp) lawnmower engine ran continuously to generate power for and recharge the batteries. The combination of power plants made the car amazingly versatile. The batteries alone could be used for trips of under 25 miles, but the car had an unlimited range as long as the generator engine was running and the driver didn't have a penchant for drag racing
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Originally Posted by Dave Arthurs
A 25-mile test run using the nine-hp diesel engine showed that a gallon of fuel could produce sufficient amperage at 36 volts to drive the car two hours at 45 mph. That's 90 miles to the gallon. If the terrain had been a bit less hilly, the average speed would have been closer to 55 mph. It's important to realize, however that stop-and-go traffic shortens the range and reduces efficiency because of the heavy current draws (600 amps) in taking off. That's where the surge current (cranking power) of the battery comes in. A great deal of city driving will certainly affect overall fuel economy.
Short trips can be made all electric, and with gasoline/electric prices about the same per kwh, an electric motor that's ~three times more efficient equates to 1/3rd of the fuel costs. And ~90mpg with a diesel "generator" at 45-55mph in a pickup sure sounds nice to me. I bet there are plenty of classic car shells that we could appropriate for this kind of system, and see great mpg numbers without having to shut the engine off, or worry about traffic, etc... Just hit the cruise control and watch 100mpg roll by.
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Old 09-16-2006, 08:13 PM   #16
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I don't think they're that bad, especially when comparing low load/high displacement to high load/low displacement gasoline engine operation. For instance Honda's small (~15hp?) GX series seems to have a minimum BSFC of 313g/kwh, and at minimal efficiency, the Prius' engine is operating at ~672g/kwh (assuming 224g/kwh is 36% eff, and 12% is triple this), so pumping losses are pretty big even in today's advanced variable valve atkinson cycle engines. Iirc a member posted that they used as much fuel at idle as they did cruising at ~35mph(?) or something. Putting a small disp engine in a gasser would work as well, but image how slow a 20-30hp 3000lb car would be...

edit- playing around with metrompg's resistance calculator and the Prius' supposed stats (Crr=.01, Cd=.26, A=2.16m^2) seems to indicate that at 50mph, the Prius' engine is only operating at ~21% efficiency, and BSFC is ~384g/kwh. I'd bet small gasoline generators designed to run at one speed could easily return ~250g/kwh.
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