Solar Powered Wheels Jerry Fetterman c. 1993 Jerry Fetterman It was in the early '80s when I first got the fever Ä electric car fever. We were paying a visit to Windy Dankoff in New Mexico and got to see his electric-powered Corvair. What a great way to dump the surplus power from a photovoltaic (PV) powered home and cut down on the use of gasoline! For the next several years, I dreamed of buying a surplus generator and a junker car (this part really worried my wife), and putting together my electric vehicle. However, I am not (or ever will be) as handy a tinkerer as Windy is, and realizing my limitations, never did accumulate the necessary parts. Not only would an electric car be a wonderful place to dump my surplus power, I thought the car would be a good way of advertising our solar business, Yellow Jacket Solar. The First Car In 1986, the battery distributor I had been dealing with turned me on to the Jet Manufacturing Corporation, a manufacturer of electric cars. Although I learned Jet was no longer in business, I was able to locate and buy a used Jet Escort hatchback. The Jet Escort Hatchback was a Ford Escort Hatchback that was converted to run on electric power. The literature available on the Jet Escort indicated that it had a range of 60 miles and a top speed of 70 mph. It ran on 96 Volts (16 golf cart batteries) and had a 12 Volt marine battery to run the electronics and lights. The battery power was delivered via an SCR controller to a 20 hp G.E. DC motor which connected directly through a stock clutch and transaxle. The first problem I ran into was how to charge the car. While it had a 220 Volt built-in charger, the only way I could charge it was through my #$&@ gas generator Ä hardly the idea I had in mind when I bought the car. I eventually rigged up a variable transformer with a full wave bridge rectifier to charge the batteries from my Heart Interface inverter, but this system was only partially successful. Since the car was supposed to show the ability of solar power at the trade shows we went to, I decided to put some solar panels on it. With 96 Volt nominal battery pack and 12 Volt nominal panels I needed 8 panels to charge it: no small financial undertaking or small array to fit on a Ford Escort. We ended up settling for eight 16 Watt panels and mounted them on a roof rack. The next problem we had with this vehicle was its limited range. While it was reported to be able to travel 60 miles on a charge, this figure must have been obtained on a downhill slope with a tail wind. Given our hilly terrain and the added friction of gravel roads, we could only get about 25 miles on a charge before the batteries were empty. Which leads to the next related problem: the voracious appetite the car had for electric power. While it didn't bother me to see 24 Volts / 60 Amps running into my inverter to power my washing machine, it really bothered me to see 96 Volts / 100-200 Amps going into the motor of the Jet Escort. With that kind of load, it took a long time for the car to charge between drives. Thus we drove the car less and less and after a year or so of owning the car, I realized that if I didn't sell it, the car would slowly deteriorate into the ground. While my electric car fever wasn't broken, the Jet Escort surely reduced it. Contemplation After selling the Escort, I got to thinking. Maybe trying to run conventional cars on electricity is like running conventional houses on solar power: it can be done but it takes lots of power and batteries. Perhaps if I applied the energy-efficient techniques used in solar home construction to to my solar car's construction, I could design a vehicle that would meet my needs yet not consume excessive amounts of power. One element of the Escort, the weight, just kept coming back to me. Because Jet Manufacturing had started with a standard, heavy American-made vehicle (albeit one of the lightest ones available), they therefore had to put in a heavy, powerful motor to propel the car, and this in turn had required numerous heavy batteries. When I figured it out, I knew I wanted to build a light electric vehicle. At the same time, I knew that building an ultralight vehicle from scratch was beyond my technical abilities. So I decided to build an electric car from a stripped-down converted donor vehicle. Since my only period of surplus power is during the summer, I decided to build a strictly summer-use car. This meant that I could forego the need for doors, roof, etc. and thus save weight. The design started to take the form of a modern horseless carriage Ä an electric buckboard. Within a short time I had decided to use a VW bug as the donor vehicles and a sand rail frame as means of lightening the framework of the bug. The sand rail frame was a good idea, but I could see that it would need some customizing. First, I didn't want a race car, where you sat on the floor of the vehicle, but rather more of a buckboard Ä a sort of Jeep with a bench seat and a pickup bed. Second, I needed room for stowing the batteries. Originally, I had really wanted a 24 Volt system running the car, since at that voltage, I could easily dump surplus power from my house. However, several electric car enthusiasts convinced me that I would be very disappointed in 24 Volt DC motor performance. I therefore decided to go with a 72 Volt 10 hp system. To minimize weight in the car, I decided to go with six 12 Volt RV marine batteries, instead of twelve 6 Volt golf cart batteries. This would save over 350 pounds in the car but would also leave me with vastly inferior batteries. In anticipation of charging the batteries, I hooked up my solar panels through a series of relays triggered by voltage sensing switches. When my house voltage got low, the panels were configured at 24 Volt nominal to charge my house batteries. When they reached 28 Volts, the panels would switch to 72 nominal and charge the car batteries to 90 Volts. At this point the panels would switch back to 24 Volts nominal to float my house batteries. While I was developing the initial design of the car, i was very lucky to meet John Davis, master mechanic and welder, and a Bug aficionado. I did the rough sketches and John did the final design work, welding, and fabrication. The end result of the vehicle is as much a result of my ideas as John's pragmatic and technological abilities. The New Car In designing and building the new solar car, we kept in mind four goals: the car should be light in weight, tough enough to handle rough roads, safe, and capable of being licensed as street legal. In order to lighten the car, we used aluminum for the fabrication of the frame and the front end beam, and replaced the stock rear torsion suspension with a coil-over-shock suspension system. It became real obvious in short order that how light the car would get would be directly proportional to how much money I wanted to put in it. The after-market products available for dune buggies and sand rails are numerous and often expensive. After indulging with some things (gas shocks that weigh only 5 pounds each) and stopping at others (disc brakes) we ended up with a relatively light vehicle that could be further lightened as funds became available. Specifications The vehicle weighs 900 pounds, of which 325 pounds are the batteries, 100 pounds are the motor, 150 pounds are the frame, and the remaining 325 pounds are the transaxle, clutch, wheels, tires, seat, etc. The power components were purchased new from Steve Van Ronk of Global Light and Power. They consist of a 10 hp (72-120 Volt DC) motor, a pulse width power controller (to vary the speed of the motor), and adapter plate to mount to the VW transaxle, a lightened flywheel, meters, and various relays and power disconnects. The power is run from six 105 Amp- hour RV/Marine batteries in series. Acceleration is quick and power is amazing. the car climbs any hill without the slightest hesitation and is wonderful on back- country 4-wheel-drive roads. Top speed on a flat surface in 4th gear is 50 mph. Faster speeds could be obtained by increasing the voltage (adding more batteries in series). Power consumption is approximately 200-300 Watt-hours per mile (0.2 -0.3 kiloWatt-hours per mile, or 3-4 Amp-hours at 72 Volts DC per mile) in hilly country on gravel roads. This is two to three times better than the 750-800 Watt-hours per mile I got with the Jet Escort. With the RV/Marine batteries my range is approximately 30 miles Ä not much better than the Escort. However, a longer range could be achieved with (you guessed it) a larger battery bank. Conclusion The vehicle I have built fits my needs wonderfully. I use it to go to our garden (3.5 miles from our house), to get the mail (7.5 miles), to visit friends, to explore back country roads, and to go to the local convenience store. It is a great vehicle for taking short trips on remote roads. The open air approach allows driver and passengers the wonderful experience of enjoying their surroundings while being whisked silently along. Doubling the satisfaction is the knowledge that the power used to propel the car is surplus power generated by solar electricity. One friend stated that driving in the car was like sailing on a boat. This car, however, is hardly the electric vehicle for everyone. Its open-air approach makes it basically useless in inclement weather, and it is of questionable safety in commuter traffic. Based on the work we have done on the car, I believe that a practical, efficient electric commuting car can be made. Such a vehicle must be light enough to cut the consumption of power. If we continue our current trend of making heavy cars and charging them on utility power, all we will have done is to substitute decentralized power production and consumption (many motors burning fossil fuels) with centralized power production and decentralized consumption (large fossil fuel burning power plants generating electricity to be used later in vehicles). We need to rethink the automobile, not just remodel it. Access Jerry Fetterman, Yellow Jacket Solar, CO ù 303-562-4884 John A. Davis, Mancos, CO ù 303-533-7105 Steve Van Ronk, Global Light and Power,