Electric Car Conversion: The Amazing 75-MPG Hybrid Car
(Page 2 of 3)
July/August 1979
By Robert W. Marshall
Of course, other components (such as relays, charging diodes, rectifiers, and an additional motor speed regulation circuit) are necessary to keep input and output power within optimum limits-and to allow full control of the vehicle at all speeds-but these are standard electrical parts which have been available for years.
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The engine-driven generator can handle the demand from the main motor up to speeds of about 50 miles per hour. The "stored" energy in the batteries comes into play at higher velocities, giving extra kick for passing and climbing hills. To guarantee that the charging system isn't overworked ... Dave has rigged up a regenerative braking circuit which- in effect-turns the drive motor into a generator, to feed the batteries when the vehicle is decelerating. (This not only takes advantage of normally wasted energy, but also saves wear and tear on the car's conventional braking system.) Since the Opel's "stock" cooling apparatus has been removed, two small thermostatically controlled electric fans provide ventilation to the motor and generator as required ... while the gasoline engine is, of course, air-cooled by design.
Growing Pains
Any project fresh off the drawing board has its share of problems, and the Opel hybrid was no exception. When David pressed the accelerator for the first time, he got a 300-amp surge which melted his relays. So he searched his graduate texts for the answer ... and finally found it in-of all places-an old high school physics book: A pulser was necessary to "chop" the current flow and prevent a heavy initial draw to the drive motor.
As Dave explains it, "The motor will always have full voltage and full current, but the pulser makes it 'think' the voltage and amperage are cut down to about 1/4 of what's actually available. With this gadget-which is simply a combination of a reworked car generator and an old fan motor-I can keep the draw within limits and effectively control the car's acceleration ... without sacrificing the maximum current or voltage that's necessary for high-speed driving. I could have achieved the same results with a commercially available FCR control ... but one of those units would have cut my power slightly, and cost in the neighborhood of $800! I can build my own device for about $25, and I can fix it myself if it breaks!"
And It's Really Practical!
Actually "piloting" the hybrid electric isn't much different from motoring in any conventional automobile. There's a slight hum from the electric motor, but the sound is certainly no more obvious than that of an internal combustion engine at speed. And-unlike many electric vehicles-the little Opel' really has some get-up-and-go ... due to the fact that the converted car is only about 50 pounds heavier than its original 2,100-pound weight.
