Mother's Own Hybrid Car!

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Furthermore, even with the battery pack fully drained and disconnected, we found it possible to motor along at a speed of 45 miles per hour on the generator engine alone. Under engine-only operation, we were still able to achieve 60.5 MPG . . . a figure which could increase by as much as 20% after the Lombardini breaks in.

What all these numbers boil down to is this: When the car is operated in the hybrid mode (using both batteries and engine as it was designed to do), it's possible to achieve astounding fuel economy over a more than reasonable commuting distance. Any driving done beyond the 78-mile hybrid range would—in our vehicle under our test conditions—be at the expense of such excellent MPG figures . . . though the numbers wouldn't ever drop to quite as "low" as the 60 (plus) MPG possible using the generator engine alone. And, of course, as long as there's fuel in the on-board diesel, the car's total range is unlimited.

BUT THERE ARESOME LIMITATIONS

The figures achieved during our testing vary from those that Robert Marshall reported were "racked up" by David Arthurs' original hybrid some months ago. Several of the discrepancies can likely be attributed to the differences in vehicles and propulsion system configurations, and others to the inequality of terrain involved. But there were several points made in that article that were inaccurate (as folks who ordered the plans, in which the errors were corrected, already know), owing to the fact that David's vehicle was then experimental and still under initial—and at times necessarily somewhat crude—testing.

For one thing, it was reported in the original piece that Mr. Arthurs' drive motor had current draws of 23 amps at 1,800 RPM. In reality, the motors that we bench-tested at 30 volts had free-running draws of about 40 amps at 4,800 RPM . . . which—under load on the highway at 30 volts—increased to 100-150 amps on level ground at 30 miles per hour, with the car in third gear.

Another point that needs some clarification is the statement, made in the article, that Arthurs' engine-driven generator could handle the demand from the main motor at speeds of up to 50 MPH, after which the energy in the batteries came into play. Our testing so far indicates that the generator, without the "hybrid" boost provided by the storage pack, is capable of propelling the car at around only 45 MPH and—at that velocity—doesn't produce enough surplus to significantly charge the battery bank.

Which brings us to another point concerning performance of the vehicle: Dave's original car was set up to use a 24/48-volt system (an option emphasized in the plans) . . . in other words, the auto could be switched to the higher voltage to achieve greater speeds for passing and such. Making a switch to "48", however, increases amperage draws drastically (causing a corresponding reduction in the vehicle's range), and—since the batteries can't be charged at 48 volts—continuous travel at such speeds would be impossible. (Furthermore, though it was reported that Dave's speedometer registered 90 MPH on a gradual downhill grade, we feel that the drive motor would have had to be fed yet more voltage—at least on level ground—to achieve such an admittedly excessive speed.)

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