GM Moves Forward with Impact Electric Car

The early 1990s brought many surprises to the advanced technology vehicle field. During this time, the most notable vehicle introduction was that of the GM Impact electric car concept at the Los Angeles Auto Show. Shortly after GM’s top management announced that the concept would become a reality, there was a flurry of activity on many fronts to make this real. GM brought all its resources to bear, from its noted research and development labs to the varied talents of its extensive supplier network. GM’s newly acquired Hughes Aircraft division also provided substantial brainpower from the aircraft and aerospace industries. At the time Green Car editors closely followed this development program and drove the early test mules at GM’s Desert Proving Grounds. This article is reprinted just as it ran in Green Car Journal’s February 1992 issue to share our thoughts on GM’s unfolding electric car efforts.

EVALUATING GM’S ELECTRIC CAR PROGRAM
ORIGINALLY PUBLISHED FEBRUARY 1992 In the two years since GM announced its intention to produce an EV based on the Impact electric vehicle prototype, the automaker has formed an electric vehicle marketing group and brought together an impressive pool of talent to focus on EV development. It has also brought to bear the full impact of its mid-'80s acquisition of high technology-laden Hughes Aircraft through wide-ranging technology transfers. And in an important strategic move, the automaker is using Hughes Systems Engineering and Program Management techniques to guide its complex future EV to market.

Specific component manufacturing sites have also been determined for the EV program. Named to date: Delco Remy Division (Muncie, Ind.) to build the batteries. GM Lansing Craft Centre (Lansing, Mich.) to assemble the vehicles. Delco Remy Plant 17 (Anderson, Ind.) to produce propulsion motors. And Hughes Power Control Systems (Torrance, Calif.) to design and manufacture power electronics and charging systems.

Green Car recently gathered first-hand knowledge of GM's electric vehicle progress at the automaker's Mesa, Ariz. proving grounds. Three electric test "mules", a specially outfitted Chevrolet Lumina APV van and two Geo Storms, were placed at our disposal. We were able to get a feel for off-the-line and passing performance and experience GM's developmental regenerative braking system. Importantly, this session also produced some hard numbers that allow an analysis of EV performance potential.

All three test vehicles were equipped with the componentry being developed for GM's coming Impact-style electric vehicle. Included: A pair of 57 hp (114 hp total) AC induction motors that drive the front wheels; dual MOSFET inverters; and a 42.5 amp-hour, 13.6 kWh battery pack with 32 series-wired 10V batteries.

Elapsed 0-60 mph (0-97 kph) test times of 12 seconds were attained by a Geo test mule. That's within 1 1/2 seconds of the 0-60 mph times attained by an internal combustion (IC) engine powered Storm, and about the same performance as some sport/utility vehicles. Data recorded by one onboard computer indicated an 8 kW power draw at 50 mph (80 kph), 13 kW at 60 mph (97 kph), and 21 kW at 70 mph (113 kph). The Storm's performance times are a full one-third slower than those projected for the Impact-style EV that GM will produce. But the Geos were handicapped with curb weights 610 lbs (277 kg) greater than the Impact prototype, and aerodynamics less favorable at 0.31 Cd vs. 0.19 Cd.

While the heavier Lumina APV was notably slower than the Storm mules, its taller gearing netted an 85 mph (137 kph) top speed, 10 mph (16 kph) faster than the Geos. The electric APV's overall performance and handling suggest the potential as a future fleet vehicle should GM decide to go this route. Certainly, APV styling is already in tune with the image of a future transport vehicle. GM sources advised Green Car that no plans are on the table at this time. In the interim, the APV serves as the perfect developmental vehicle since its cavernous interior allows straightforward testing of various battery configurations.

The only developmental glitch experienced during our testing was with one Storm's inverter, a problem that temporarily affected the synchronous operation of its front-drive motors. This was later remedied. The APV and second Storm did not experience a similar problem. GM Hughes Electronics is currently working on the program's second-generation inverter to make it a low-cost, reliable, and manufacturable unit for a production EV. "To develop the inverter, we have adopted an approach used with the Strategic Defense Initiative Project," shares James Abrahamson, Executive Vice President at Hughes Aircraft Co. "This approach is to work concurrently on several generations of technology at the same time... and the payoff is real." Improvements over the original prototype have found the total number of parts reduced by 85% and costs cut by 97%.

Test sessions like these are eye-opening. But they do leave certain important questions, most notably range, unanswered. When battery power is heavily tapped by quick off-the-line starts and relatively high speeds, range is greatly compromised. Physical laws dictate that an EV will go farther with gentle acceleration and moderate speeds. Unfortunately, not all motorists drive this way.

While this test session was not designed to establish range parameters, Green Car editors feel safe in concluding that a 120 mile jaunt was not in the cards for any of these vehicles on this test day. But the fact that these EVs did accelerate and handle well, and felt so conventionally car-like in many respects, make this a very important milestone for GM and its electric vehicle program.