view of Electric Cars
News1.net New York March 4, 2010 By Frank X. Didik
and Answers regarding Electric Vehicles
Since the early 1980's, I have designed and built about 20 solar, electric and non gasoline powered vehicles. I am also the founder of the Electric Car Owners Club (now known as the Electric Car Society). The following is an answer to many common questions and addresses some of the misconceptions that people have regarding electric cars with respect to pollution, safety, pollution and economy issues.
Overview: Electric cars are in many ways similar to gasoline powered cars. They can be comfortable, reliable and handle well. Electric cars are very quiet. So quiet that you can barely hear the motor run, even at top speed. This silence can be a danger to pedestrians crossing the street since pedestrians can not hear the car coming. An electric car operator must be constantly aware of this problem while driving in populated areas. Until recently, most electric cars fell into two categories--cars converted from gasoline power, such as a VW or a Chevy Chevette or tiny cars such as Citi-Car and CommutaCars from the mid 1970's to the early 1980's. . In the case of the Citi-Car, the normal range in the summer of about 40 miles and in the winter time about 30 miles per charge. With intermittent charging throughout the day, the range can be extended up to 70 miles per day. The average driver drives an estimated 28 miles per day. Most electric cars today have built in battery chargers and all that is required to recharge is a long extension cord and plug into a regular 110 Volt home outlet. It takes about 7 hours to fully recharge the batteries. It is possible to greatly reduce the charging time by increasing the charging voltage, however by doing this, the life of the batteries is shortened. The Citi-Car uses eight special 6 volt "deep cycle" batteries, which are also commonly known as marine batteries. These batteries weigh more then normal car batteries and are designed to endure up to 2000 charges. Under normal conditions, this translates to about two years of use. A set of eight deep cycle batteries can cost as little as $800. When the cost of replacing the batteries and the cost to recharge the batteries are considered, the cost to run a small electric car (non-hybrid) is about three times more than a conventional economy gasoline car. Since the cost of electricity tends to more or less follow the cost of fuel, it is unlikely that this ratio will change in the future. Electric cars are fun to have and drive, but you will not save money, nor will you really help the environment.
Converting a car from gasoline to electric: It is possible to convert any vehicle to electric, however the frame of a convention car would have to be greatly strengthened in order to sustain the weight of the batteries. I would have to say that the vast majority of conversions, which I have seen would have seen, would have to be considered almost unacceptable. In most cases, the end result is too heavy, underpowered, very short range and low top speed. From what I have observed, the person converting the vehicle has a conventional gasoline powered car that has a bad motor or the person has access to a smaller car at a very favorable price. After removing the existing gasoline engine, the chases is strengthened and a rather heavy (and expensive) load of batteries are installed, in most cases in the trunk and under the rear seat of the vehicle. The gasoline engine being replaced by a 10 to 20hp dc electric motor or an ac motor with a power inverter. The result is a vehicle that is now anywhere from 700lbs to 1500lbs (300kg to 600kg) heavier than the original gasoline powered car, even taking into consideration the removal of the heavy gasoline engine. In many cases, the original car was only 2000lbs and is now 1/3 heavier. Since the original vehicle was never designed for such a heavy weight, the stability and handling are often adversely effected. Conversions often seem to have a range of 25 to 40 miles and a top speed of 50mph. These dismal figures are rarely exceeded ... from what I have observed. Sadly, I have noticed many exaggerated claims in the press, regarding top sped and range. Prior to converting the vehicle, most people had expected far greater performance. Another factor in home conversions is that the projects are often not completed, since the person converting either loses interest or runs into minor technical problems or can not find specific parts. I have seen a wide variety of conversions including a Porsche 914, Saab, fiat 850, Chevrolet Vans, Renault LeCars (R5), VW Beatles and VW buses. Perhaps surprisingly, the most successful conversions seem to be the VW bus. I think that the reason is that the frame is relatively strong to begin with, so that the batteries have a relatively good base and the VW bus is a rather light weight vehicle.
Cost of operating an electric vehicle (non-hybrid): On average, a straight electric (non-hybrid) car, which uses standard deep cycle lead acid marine type batteries and is charged from the mains, costs about 3 times more to run than a conventional gasoline car. From a financial point of view, a diesel car, running on something like filtered, used vegetable oil, such as the discarded oil from restaurants, might be a better solution, however, the effort in doing the conversion and in acquiring the used oil might not be worth the effort. Perhaps buying an economy car such as a Ford Aspire (43mpg), Honda Civic or one of the hybrids, such as the Toyota Prius, might also be a solution. If gasoline should ever become difficult to obtain (which, for the moment, seems unlikely), it may be possible to use an electric car charged from such local sources as wind power, or less likely, because of the high price of solar cells, solar power.
Do electric vehicles pollute?: Electric vehicles do pollute, though most of the pollution is at the point of electric generation. Though the electric car itself does not burn fuel, most power plants use "fossil" fuels to generate electricity, so we must consider the pollution created at the power plant. Another issue that is rarely addressed is the fact that most electric cars use batteries which themselves have the potential to pollute if they are not disposed of correctly. In many cases, batteries, while they are being charged, gives off gasses, which can vary depending upon the type of battery. This can be hydrogen and oxygen or sulfur fumes or other gases. Hydrogen and Oxygen themselves are not considered pollution of course, however the mixture can be explosive if they are allowed to reform water. Another type of pollution that may be of concern is the electro-magnetic emissions that some people feel can cause various human ailments. Electric motors can be shielded with special alloys, such as a highly tempered copper/nickel alloy, creating a type of Faraday cage, however this adds weight to the vehicle and it is not conclusive that all emissions can be contained.
WHAT ABOUT SOLAR POWER? With current technology, it is not possible to effectively run a car directly from the sun. So-called solar powered cars are in reality solar charging battery powered cars. The sun is used to charge the batteries. Nevertheless, there have been remarkable developments in the area of solar cells and in the development of ultra light weight solar charging battery powered cars. For example, the GM Sunraycer, weighs 390 lbs, is 3.3 feet high, 6.6 feet wide and 19.7 feet long and averaged 41.6 miles per hour over a total of 44.9 driving hours. The GM Sunraycer is considered one of the most advanced "solar" cars in the world and in 1987 won the Solar Challenge race in Australia--a 1,950 mile race. Other solar cars have attained speeds of over 110 mile per hour.
Are Electric vehicles safe?: These days, some people are concerned with the electromagnetic emissions of cell phones. It should be pointed out that the electromagnetic emissions emitted from an electric car is many times greater than that of a cell phone. Please also refer to the paragraph above entitled "Do Electric Vehicles Pollute?". There are many different types and sizes of electric cars. Most electric cars are much heavier then they look, due mostly to the weight of the batteries. The Citi-Car for example, weighs about 1600 lbs. Since most electric cars are limited production cars, they are built the same way as most racing cars--with tubular steel frames. As a result, most electric cars are structurally very strong--stronger then most conventionally produced gasoline cars!
Acceleration: An electric motor has what is known as continuous torque and therefor has almost the same horsepower at any speed, though an electric motor is more efficient at high rotational speeds. For this reason, an electric car normally has better acceleration from standstill of then the acceleration of a gasoline powered car! The Citi-Car can out accelerate most cars from 0 to 20 miles per hour. The top speed of the Citi-Car is however only 40 miles per hour.
What kind of DC motors you use? To save weight, I use low HP (horse power) motors, usually between 3 and 6HP to power a car that has a total weight of 1800pounds (including batteries). This is enough power to move the vehicle between 35 and 55 miles per hour. This means that the car weighs about 800kg and can travel between 50km and 90km per hour. A normal small gasoline car, such as the old (1972) VW 1300cc Beatle has about 18hp and can travel up to 110km hour. An electric motor has continuous torque and has different properties than a gasoline engine. At 100km per hour, a normal car weighing 1000kg, only needs to have a 7hp motor to keep going at 100km an hour. The problem is acceleration and the time it takes to go 100km per hour.
What is the average speed that
can be reached with such a motor?
Should I use 4 separate motors (1 for every wheel) to get the best in performance or would it be better to use 1 in the front and 1 in the back of the car and linking the two together? This system of using motors in every wheel was first used over 100 years ago. The problem with this setup is that it is difficult to keep each wheel at an exact constant speed. It leads to an instable car, in most cases.
Can I recharge the batteries by placing a generator or an alternator on the electric motor, so that I can drive indefinitely? No. This setup will not work since there is a concept of conservation of energy and therefore, it would take the same (or more) energy to recharge the batteries, thus the car would not move. This is also known as perpetual motion and is contrary to the know and established laws of physics. It should be noted however, that while braking the car, you can slow it down by converting the forward motion of the car into electricity that can be redirected to the batteries. This is known as regenerative braking. From my perspective, the added weight and complexity of the regenerative braking system, plus the low absorption efficiency rate of conventional batteries, ultimately provides for little if any gain in range for the vehicle. In the case of long range driving, with little braking required, the added weight of the regenerative braking system, probably reduces range somewhat.
How many batteries will I need to run a small two person electric vehicle? In general, to run a small electric vehicle, weighing 700lbs, without batteries, you will probably use between 8 and 10 6 volt batteries for a combined voltage would be from 48 to 60 or more volts.
More about batteries including the time consuming issues regarding charging: If you are using conventional 6 or 12 volt "deep cycle" batteries, the charging time will be about 8 hours per day. Once a week, it will be necessary to take the caps off of all of the cells and top the cells off with distilled water and then charge the batteries for 12 hours. If one cell in the battery array is bad, it is important to replace the battery immediately, since that one cell with drain the charge from the entire battery array. Lead acid batteries have what is referred to as a memory. This is a very inconvenient phenomenon whereby if you re-charge the batteries before they are fully discharged, over time, the batteries will remember that point and this will actually reduce the amount of electricity that can be stored in the battery. If your battery pack, when fully charged, is able to let you drive 40 miles and you drive 30 miles to a particular location, it is possible to charge the batteries for an hour or two and then have the necessary power to go the additional 20 miles to complete your 60 mile round trip. The problems that arise in this case again, is the memory issue. As mentioned above, a fully discharged set of batteries requires 7 to 8 hours of charging, but it is interesting to note that within two to three hours, the batteries are charged to an 80% level. This means that most charging occurs in the first few hours. Again, however, if you charge your batteries for only a few hours, the batteries will be greatly effected by the memory issue and will rapidly decline in overall output.
Should I use a gearbox, if I build an electric car? Hard to say, though most car companies use gear boxes. Perhaps a bicycle transmission or a transmission from an old DAF car would be a good idea. You may also be able to adapt standard machine tool components that have variable speed Vbelt adjusters. For optimum efficiency, it is better for an electric motor to spin at a higher rpm (revolutions per minute) so that gearing, when starting from a standstill, can measurably increase performance and duration. In the case of a gasoline engine, the opposite is true, in that for maximum mpg (miles per gallon), it is important to keep the engine running at a relatively low rpm.
Should I use an electronic voltage control system or an electro-mechanical system? I use all types of systems, but I find that the electric savings using a fully electronic system is so small, that it is not worth the effort and expense of the equipment.
Should I make the body out of fiberglass, carbon fiber, aluminum or what else? These are basic car design issues. I think that fiberglass is too heavy. Perhaps a lightweight frame and then use shaped Styrofoam covered with a very thin coating or thin plastic. UV sunlight can destroy many types of plastic in just a year or two. I believe that carbon fiber is vastly over rated for a number of reasons. Though in theory, carbon fiber is extremely light and at the same time, is substantially stronger than steel, I have noticed that all too often, parts made of carbon fiber are not well designed and thus the potential weight advantage is not achieved. Further, if a carbon fiber component is not well engineered, it can, in fact, fracture. In general, the material that you feel most comfortable and most experienced to work with is probably the best material to use, but you should always, at all phases of both design and construction, keep weight down, but at the same time, do not compromise safety. I have seen strong, effective vehicles made out of a light weight tubular frame with stretched and shrunk thin film mylar used for the side and rear panels. The problem of mylar is that it is greatly effected by UV light and degenerates, under normal conditions, in less than two years. I have also seen the same using thin canvas. -Original article can be found at: http://www.didik.com/criticalev.htm
© 1977 - 2010 Frank X. Didik