Epic EV Conversion Time: Keith’s Corvette
The Chevy Corvette. A storied model with a legacy of high performance known worldwide. Equally at-home cruising Main Street, ripping down the quarter-mile, enduring Le Mans, and now, thanks to Keith Stegath, green as green can be in true EV style. What possesses a man to convert a Corvette to electric power? Here’s the story.
Tell us a little bit about yourself, sir: name, location, what you do for a living?
I’m Keith Stegath and I moved with my wife to Gainesville, Florida, in 1999. For 40+ years, I lived in (or near) Ann Arbor, Michigan where I was heavily involved in the automotive industry. In 1978, I graduated from Ferris State University in Big Rapids, MI, with an Associate Degree in Automotive Technology and a Machinist Certificate for Performance Engines. In 2005, I received a Bachelor of Science in Electrical Engineering and, in 2007, and I received a Master of Science in Mechanical Engineering, both of which came from the University of Florida.
My current job is as a research engineer where I investigate methods for capturing the electrical energy produced from piezoelectric materials.
Now tell us a little bit about your automotive background: what automotive projects lead you to this one?
My automotive and mechanical background started as a 10 year-old fabricating and building go-karts. It progressed to the usual performance modification of automobiles. I worked as an auto mechanic and then as a machinist and CNC programmer. After 15 years in the CAD/CAM software industry, I returned to my roots and started a business, Stegath Coachcraft, customizing cars and complete automobile restorations. My focus was on Corvettes, but I also accepted other vehicles.
Why are you building your own EV?
As Clint Eastwood’s Dirty Harry once said, “A person has to know his limitations.” The fundamentals for converting car to electric are very straightforward; the challenge is making a quality conversion that is on par with a well designed a new car. A quality conversion does not have wires strewn around in a rat’s nest. A quality conversion does not use a rigid choke-cable poking through the firewall for the emergency disconnect. A quality conversion does not use wood 2x4s. So I decided to build a quality electric car.
Why did you decide to convert a Corvette?
When I had my business restoring cars, I had a 1976 Corvette that I was restoring and customizing. The car had been sitting in the garage gathering dust for about 10 years and I was going to part it out, but I had put a lot of time modifying and repairing the body so I didn’t want to send it to the junk yard. Then I thought, “Hey, I’m a green kind of guy; why not convert it to electric?”
How is this EV conversion similar to more traditional automotive builds?
How is it different? Are there any special design/fabrication challenges?
There are far more differences than commonalities between a Corvette EV conversion and a restoration or engine swap; a quality conversion required a lot more planning.
Commonalities
Rear window defogger
Radio antennae
Differences
The Big Issues
- Mounting the motor in a car that had a full frame.
- How to cram 24 full sized lead-acid batteries (1200 lbs) in a Corvette.
- Updating the dash so that it made use of new technologies, and remove gauges that were no longer useful.
- Installing a manual transmission
- High voltage and high current
- Swapped the rusted out 1976 frame for a clean 1982 frame
Other issues
- Brakes – need a vacuum source for the brake booster
- Parking brake – need a quality parking brake (a Corvette weakness) since the parking function of the automatic transmission is no longer available
- Steering – non-power assisted steering was an option for the early Corvettes, so I converted to non-power assisted steering
- Air Conditioning – convert the A/C from R12 to R134; design a 90 volt, 20 amp power supply for a 2.75hp electric motor that drives the compressor; add electric fans for the front condenser; mount the electric motor/compressor in the rear of the car.
- Heater – replace the hot water heater core with a 1500 watt electric unit
- Suspension requirements with 1200 lbs of redistributed weight:
- Front – 600 lbs of batteries, 230 lb motor. Installed coil-over shocks for easy height adjustment.
- Rear – 600 lbs of batteries. The fiberglass leaf spring only required longer bolts for easy height adjustment.
- Mount accelerator potentiometer under the dash
- Add & remove wires to the factory wire-harness bulkhead connector
- Integrate numerous and redundant electrical safety interlocks & relays
- Emergency disconnect switch – using two high-amp circuit breakers (one for each pack of 12 batteries)
What’s a particularly vexing obstacle you’ve had to overcome with this project? How did you solve this problem?
The motor/transmission crossmember was a time-consuming design and fabrication process. I made a CAD model to create and analyze a lot of the components. Using dimensioned drawing, I made a to-scale solid model of the frame, crossmember, battery pack.
I didn’t want to weld the crossmember and I wanted it relatively light, so I made it from T6-6061 aluminum all bolted together with interlocking pieces.
How will you use this Corvette once it’s completed and what are your performance targets?
I work less than 10 miles from home so the car will be used as a daily driver. Computer simulation suggests that with 144 volts and 1,400 amps the car should run the 1/4 mile under 15 seconds. With a light foot and 120 amp/hr of battery power I’m hoping for 50-60 miles per charge.
Where can we find out more information and connect with you online?
I can be contacted at: kstegath (at) gmail or Advanced-EV.
What’s next on the agenda?
The car may never be finished; I’ll keep making changes to it. I have plans for regenerative braking, a new battery pack, and of course you can never push too many amps through the motor.
Gearheads United!
- Do you think you could “go green” in an EV like this one?
- What do you think of Keith’s engineering and fabrication skills?
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