Electric cars use electric motors to generate the kinetic energy necessary. They use electrical energy stored in batteries. Sometimes the battery is supplemented by a small gasoline engine as a backup. Electric cars have been around for over a century but never been able to compete with cars outfitted with internal combustion engines.
As of January 2012 series production models available in some countries include the Tesla Roadster, REVAi, Renault Fluence Z.E., Buddy, Mitsubishi i MiEV, Tazzari Zero, Nissan Leaf, Smart ED, Wheego Whip LiFe, Mia electric, BYD e6, and Bolloré Blue Car. The Leaf, with more than 21,000 units sold worldwide through December 2011, and the i-MiEV, with global cumulative sales of more than 17,000 units through October 2011, are the world’s top selling highway-capable electric cars.
Electric cars have several potential benefits as compared to conventional internal combustion automobiles that include a significant reduction of urban air pollution as they do not emit harmful tailpipe pollutants from the onboard source of power at the point of operation (zero tail pipe emissions); reduced greenhouse gas emissions from the onboard source of power depending on the fuel and technology used for electricity generation to charge the batteries; and less dependence on foreign oil, which for the United States, other developed and emerging countries is cause of concerns about their vulnerability to price shocks and supply disruption. Also for many developing countries, and particularly for the poorest in Africa, high oil prices have an adverse impact on their balance of payments, hindering their economic growth.
Despite their potential benefits, widespread adoption of electric cars faces several hurdles and limitations. As of 2011 electric cars are significantly more expensive than conventional internal combustion engine vehicles and hybrid electric vehicles due to the additional cost of their lithium-ion battery pack. However, battery prices are coming down with mass production and expected to drop further. Other factors discouraging the adoption of electric cars are the lack of public and private recharging infrastructure and the driver’s fear of the batteries running out of energy before reaching their destination (range anxiety) due to the limited range of existing electric cars. Several governments have established policies and economic incentives to overcome existing barriers, to promote the sales of electric cars, and to fund further development of electric vehicles, more cost-effective battery technology and their components. The U.S. has pledged US$2.4 billion in federal grants for electric cars and batteries. China has announced it will provide US$15 billion to initiate an electric car industry within its borders. Several national and local governments have established tax credits, subsidies, and other incentives to reduce the net purchase price of electric cars and other plug-ins.
Electric cars are a variety of electric vehicle (EV); the term “electric vehicle” refers to any vehicle that uses electric motors for propulsion, while “electric car” generally refers to road-going automobiles powered by electricity. While an electric car’s power source is not explicitly an on-board battery, electric cars with motors powered by other energy sources are generally referred to by a different name: an electric car powered by sunlight is a solar car, and an electric car powered by a gasoline generator is a form of hybrid car. Thus, an electric car that derives its power from an on-board battery pack is a form of battery electric vehicle (BEV). Most often, the term “electric car” is used to refer to pure battery electric vehicles.
1990s to present: Revival of mass interest
The energy crises of the 1970s and 80s brought about renewed interest in the perceived independence that electric cars had from the fluctuations of the hydrocarbon energy market. In the early 1990s, the California Air Resources Board (CARB) began a push for more fuel-efficient, lower-emissions vehicles, with the ultimate goal being a move to zero-emissions vehicles such as electric vehicles. In response, automakers developed electric models, including the Chrysler TEVan, Ford Ranger EV pickup truck, GM EV1 and S10 EV pickup, Honda EV Plus hatchback, Nissan lithium-battery Altra EV miniwagon and Toyota RAV4 EV. These cars were eventually withdrawn from the U.S. market.
First Nissan Leaf delivered in the U.S. on the road south of San Francisco
The global economic recession in the late 2000s led to increased calls for automakers to abandon fuel-inefficient SUVs, which were seen as a symbol of the excess that caused the recession, in favor of small cars, hybrid cars, and electric cars. California electric car maker Tesla Motors began development in 2004 on the Tesla Roadster, which was first delivered to customers in 2008. As of January 2011 Tesla had produced more than 1,500 Roadsters sold in at least 31 countries. The Mitsubishi i MiEV was launched for fleet customers in Japan in July 2009, and for individual customers in April 2010, followed by sales to the public in Hong Kong in May 2010, and Australia in July 2010 via leasing.
Retail customer deliveries of the Nissan Leaf in Japan and the United States began in December 2010, though initial availability is restricted to a few launch markets and in limited quantities. As of September 2011 other electric automobiles, city cars, and light trucks available in some markets included the REVAi, Buddy, Citroën C1 ev’ie, Transit Connect Electric, Mercedes-Benz Vito E-Cell, Smart ED, Wheego Whip LiFe, and several neighborhood electric vehicles.
Comparison with internal combustion engine vehicles
An important goal for electric vehicles is overcoming the disparity between their costs of development, production, and operation, with respect to those of equivalent internal combustion engine vehicles (ICEVs).
Sales of the Mitsubishi i MiEV to the public began in Japan in April 2010, in Hong Kong in May 2010 and in Australia in July 2010.
Electric cars are generally more expensive than gasoline cars. The primary reason is the high cost of car batteries. US and British car buyers seem to be unwilling to pay more for an electric car. This prohibits the mass transition from gasoline cars to electric cars. A survey taken by Nielsen for the Financial Times has shown that 65 percent of Americans and 76 percent of Britons are not willing to pay more for an electric car above the price of a gasoline car. Also a report by J.D. Power and Associates claims that about 50 percent of U.S. car buyers are not willing to spend more than US$5,000 on a green vehicle above the price of a petrol car despite their concern about the environment.
The Nissan LEAF is the most affordable five door family electric car in the U.S. at a price of US$32,780 going down to US$25,280 after federal tax rebate of US$7,500, going further down to US$20,280 after the US$5,000 tax rebate in California and similar incentives in other states.
The Renault Fluence Z.E. five door family saloon electric car will be priced at less than US$20,000 before any U.S. federal and state tax rebates are applied. It will be sold without the battery thus the significant price difference. The customer will buy the Renault Fluence Z.E. with a contract to lease the battery from the company Better Place.
The electric car company Tesla Motors is using laptop battery technology for the battery packs of their electric cars that are 3 to 4 times cheaper than dedicated electric car battery packs that other auto makers are using. While dedicated battery packs cost $700–$800 per kilowatt hour, battery packs using small laptop cells cost about $200. That could potentially drive down the cost of electric cars that are using Tesla’s battery technology such as the Toyota RAV4 EV and the Smart ED as well as their own upcoming 2014 models such as the Model X.
A study published in 2011 by the Belfer Center, Harvard University, found that the gasoline costs savings of plug-in electric cars over the vehicles’ lifetimes do not offset their higher purchase prices. This finding was estimated comparing their lifetime net present value at 2010 purchase and operating costs for the U.S. market, and assuming no government subidies. According to the study estimates, a PHEV-40 is US$5,377 more expensive than a conventional internal combustion engine, while a battery electric vehicle is US$4,819 more expensive. The study also examined how this balance will change over the next 10 to 20 years, assuming that battery costs will decrease while gasoline prices increase. Under the future scenarios considered, the study found that BEVs will be significantly less expensive than conventional cars (US$1,155 to US$7,181 cheaper), while PHEVs, will be more expensive than BEVs in almost all comparison scenarios, and only less expensive than conventional cars in an scenario with very low battery costs and high gasoline prices. The reason for the different savings among plug-in cars is due to the fact that BEVs are simpler to build and do not use liquid fuel, while PHEVs have more complicated powertrains and still have gasoline-powered engines.
Running costs and maintenance
The Tesla Roadster is sold in the US and Europe and has a range of 245 miles per charge.
Most of the running cost of an electric vehicle can be attributed to the maintenance and replacement of the battery pack because an electric vehicle has only around 5 moving parts in its motor, compared to a gasoline car that has hundreds of parts in its internal combustion engine. Electric cars have expensive batteries that must be replaced but otherwise incur very low maintenance costs, particularly in the case of current Lithium based designs.
To calculate the cost per kilometer of an electric vehicle it is therefore necessary to assign a monetary value to the wear incurred on the battery. This can be difficult due to the fact that it will have a slightly lower capacity each time it is charged and is only considered to be at the end of its life when the owner decides its performance is no longer acceptable. Even then an ‘end of life’ battery is not completely worthless as it can be re-purposed, recycled or used as a spare.
Since a battery is made of many individual cells that do not necessarily wear evenly, periodically replacing the worst of them can retain the vehicle’s range.
The Tesla Roadster’s very large battery pack is expected to last seven years with typical driving and costs US$12,000 when pre-purchased today. Driving 40 miles (64 km) per day for seven years or 102,200 miles (164,500 km) leads to a battery consumption cost of US$0.1174 per 1 mile (1.6 km) or US$4.70 per 40 miles (64 km). The company Better Place provides another cost comparison as they anticipate meeting contractual obligations to deliver batteries as well as clean electricity to recharge the batteries at a total cost of US$0.08 per 1 mile (1.6 km) in 2010, US$0.04 per mile by 2015 and US$0.02 per mile by 2020. 40 miles (64 km) of driving would initially cost US$3.20 and fall over time to US$0.80.
In 2010 the U.S. government estimated that a battery with a 100 miles (160 km) range would cost about US$33,000. Concerns remain about durability and longevity of the battery.
Nissan estimates that the Leaf’s 5 year operating cost will be US$1,800 versus US$6,000 for a gasoline car. The documentary film Who Killed the Electric Car? shows a comparison between the parts that require replacement in a gasoline powered cars and EV1s, with the garages stating that they bring the electric cars in every 5,000 mi (8,000 km), rotate the tires, fill the windshield washer fluid and send them back out again.
Electricity vs. hydrocarbon fuel
“Fuel” cost comparison: the Tesla Roadster sport car’s plug-to-wheel energy use is 280 W·h/mi. In Northern California, the local electric utility company PG&E says that “The E-9 rate is mandatory for those customers that are currently on a residential electric rate and who plan on refueling an EV on their premises.” Combining these two facts implies that driving a Tesla Roadster 40 miles (64 km) a day would use 11.2 kW·h of electricity costing between US$0.56 and US$3.18 depending on the time of day chosen for recharging. For comparison, driving an internal combustion engine-powered car the same 40 miles (64 km), at a mileage of 25 miles per US gallon (9.4 L/100 km; 30 mpg-imp), would use 1.6 US gallons (6.1 l; 1.3 imp gal) of fuel and, at a cost of US$4 per 1 US gallon (3.8 l; 0.83 imp gal), would cost US$6.40.
The Tesla Roadster uses about 17.4 kW·h/100 km (0.63 MJ/km; 0.280 kW·h/mi), the EV1 used about 11 kW·h/100 km (0.40 MJ/km; 0.18 kW·h/mi). Other electric vehicles such as the Nissan Leaf are quoted at 21.25 kW·h/100 km (0.765 MJ/km; 0.3420 kW·h/mi) by the US Environmental Protection Agency. These differences reflect the different design and utility targets for the vehicles, and the varying testing standards. The actual energy use is greatly dependent on the actual driving conditions and driving style.
Range and refuelling time
Cars with internal combustion engines can be considered to have indefinite range, as they can be refuelled very quickly almost anywhere. Electric cars often have less maximum range on one charge than cars powered by fossil fuels, and they can take considerable time to recharge. This is a reason that many automakers marketed EVs as “daily drivers” suitable for city trips and other short hauls. The average American drives less than 40 miles (64 km) per day; so the GM EV1 would have been adequate for the daily driving needs of about 90% of U.S. consumers. Nevertheless, people can be concerned that they would run out of energy from their battery before reaching their destination, a worry known as range anxiety.
The Tesla Roadster can travel 245 miles (394 km) per charge; more than double that of prototypes and evaluation fleet cars currently on the roads. The Roadster can be fully recharged in about 3.5 hours from a 220-volt, 70-amp outlet which can be installed in a home.
One way automakers can extend the short range of electric vehicles is by building them with battery switch technology. An EV with battery switch technology and a 100 miles (160 km) driving range will be able to go to a battery switch station and switch a depleted battery with a fully charged one in 59.1 seconds giving the EV an additional 100 miles (160 km) driving range. The process is cleaner and faster than filling a tank with gasoline and the driver remains in the car the entire time, but because of the high investment cost, its economics are unclear. As of late 2010 there are only 2 companies with plans to integrate battery switching technology to their electric 2010 and announced a commitment to open four battery switch stations in California, USA.
Another way is the installation of DC Fast Charging stations with high-speed charging capability from three-phase industrial outlets so that consumers could recharge the 100 mile battery of their electric vehicle to 80 percent in about 30 minutes. A nationwide fast charging infrastructure is currently being deployed in the US that by 2013 will cover the entire nation. DC Fast Chargers are going to be installed at 45 BP and ARCO locations and will be made available to the public as early as March 2011. The EV Project will deploy charge infrastructure in 16 cities and major metropolitan areas in six states. Nissan has announced that 200 of its dealers in Japan will install fast chargers for the December 2010 launch of its Leaf EV, with the goal of having fast chargers everywhere in Japan within a 25 mile radius.
In July 2011, there are hints that Whole Foods, Walmart, etc. will be adding various charging stations.
Air pollution and carbon emissions
Sources of electricity in the U.S. in 2009.
Electric cars contribute to cleaner air in cities because they produce no harmful pollution at the tailpipe from the onboard source of power, such as particulates (soot), volatile organic compounds, hydrocarbons, carbon monoxide, ozone, lead, and various oxides of nitrogen. The clean air benefit is usually local because, depending on the source of the electricity used to recharge the batteries, air pollutant emissions are shifted to the location of the generation plants. The amount of carbon dioxide emitted depends on the emission intensity of the power source used to charge the vehicle, the efficiency of the said vehicle and the energy wasted in the charging process.
For mains electricity the emission intensity varies significantly per country and within a particular country it will vary depending on demand, the availability of renewable sources and the efficiency of the fossil fuel-based generation used at a given time. Charging a vehicle using off-grid renewable energy yields very low carbon intensity (only that to produce and install the off-grid generation system e.g. domestic wind turbine).
An EV recharged from the existing US grid electricity emits about 115 grams of CO2 per kilometer driven (6.5 oz(CO2)/mi), whereas a conventional US-market gasoline powered car emits 250 g(CO2)/km (14 oz(CO2)/mi) (most from its tailpipe, some from the production and distribution of gasoline). The savings are questionable relative to hybrid or diesel cars (according to official British government testing, the most efficient European market cars are well below 115 grams of CO2 per kilometer driven, although a study in Scotland gave 149.5gCO2/km as the average for new cars in the UK), but would be more significant in countries with cleaner electric infrastructure. In a worst-case scenario where incremental electricity demand would be met exclusively with coal, a 2009 study conducted by the World Wide Fund for Nature and IZES found that a mid-size EV would emit roughly 200 g(CO2)/km (11 oz(CO2)/mi), compared with an average of 170 g(CO2)/km (9.7 oz(CO2)/mi) for a gasoline-powered compact car. This study concluded that introducing 1 million EV cars to Germany would, in the best-case scenario, only reduce CO2 emissions by 0.1%, if nothing is done to upgrade the electricity infrastructure or manage demand.
In France, which has a clean energy grid, CO2 emissions from electric car use would be about 12g per kilometer.
A study made in the UK in 2008 concluded that electric vehicles had the potential to cut down carbon dioxide and greenhouse gas emissions by at least 40%, even taking into account the emissions due to current electricity generation in the UK and emissions relating to the production and disposal of electric vehicles.
A 2011 report prepared by Ricardo found that hybrid electric vehicles, plug-in hybrids and all-electric cars generate more carbon emissions during their production than current conventional vehicles, but still have a lower overall carbon footprint over the full life cycle. The initial higher carbon footprint is due mainly to battery production. As an example, the study estimated that 43 percent of production emissions for a mid-size electric car are generated from the battery production.
Acceleration and drivetrain design
Electric motors can provide high power-to-weight ratios, and batteries can be designed to supply the large currents to support these motors.
Although some electric vehicles have very small motors, 15 kW (20 hp) or less and therefore have modest acceleration, many electric cars have large motors and brisk acceleration. In addition, the relatively constant torque of an electric motor, even at very low speeds tends to increase the acceleration performance of an electric vehicle relative to that of the same rated motor power internal combustion engine. Another early solution was American Motors’ experimental Amitron piggyback system of batteries with one type designed for sustained speeds while a different set boosted acceleration when needed.
Electric vehicles can also use a direct motor-to-wheel configuration which increases the amount of available power. Having multiple motors connected directly to the wheels allows for each of the wheels to be used for both propulsion and as braking systems, thereby increasing traction. In some cases, the motor can be housed directly in the wheel, such as in the Whispering Wheel design, which lowers the vehicle’s center of gravity and reduces the number of moving parts. When not fitted with an axle, differential, or transmission, electric vehicles have less drivetrain rotational inertia. However, housing the motor within the wheel can increase the unsprung weight of the wheel, which can have an adverse effect on the handling of the vehicle.
A gearless or single gear design in some EVs eliminates the need for gear shifting, giving such vehicles both smoother acceleration and smoother braking. Because the torque of an electric motor is a function of current, not rotational speed, electric vehicles have a high torque over a larger range of speeds during acceleration, as compared to an internal combustion engine. As there is no delay in developing torque in an EV, EV drivers report generally high satisfaction with acceleration.
The disadvantage of providing high acceleration by high torque from the motor is lowered efficiency due to higher losses in the form of Joule heating in the motor windings caused by the high electric current. This energy loss increases fourfold as the input current is doubled, so the practical limit for sustained torque from an electric motor depends on how well it can be cooled during operation. There is always a compromise between torque and energy efficiency. This limits the top speed of electric vehicles operating on a single gear due to the need to limit the required torque and maintain efficiency at low vehicle speeds.
For example, the Venturi Fetish delivers supercar acceleration despite a relatively modest 220 kW (295 hp), and top speed of around 160 km/h (100 mph). Some DC motor-equipped drag racer EVs, have simple two-speed manual transmissions to improve top speed. The Tesla Roadster 2.5 Sport can accelerate from 0 to 60 mph (97 km/h) in 3.7 seconds with a motor rated at 215 kW (288 hp).
Also the Wrightspeed X1 prototype created by Wrightspeed Inc is the worlds fastest street legal electric car. With an acceleration of 0-60 mph in 2.9 seconds the X1 has bested some of the worlds fastest sports cars.
Production and conversion electric cars typically use 10 to 23 kW·h/100 km (0.17 to 0.37 kW·h/mi). Approximately 20% of this power consumption is due to inefficiencies in charging the batteries. Tesla Motors indicates that the vehicle efficiency (including charging inefficiencies) of their lithium-ion battery powered vehicle is 12.7 kW·h/100 km (0.21 kW·h/mi) and the well-to-wheels efficiency (assuming the electricity is generated from natural gas) is 24.4 kW·h/100 km (0.39 kW·h/mi).
The safety issues of BEVs are largely dealt with by the international standard ISO 6469. This document is divided in three parts dealing with specific issues:
- On-board electrical energy storage, i.e. the battery
- Functional safety means and protection against failures
- Protection of persons against electrical hazards.
Risk of fire
Frontal crash test of a Volvo C30 DRIVe Electric to assess the safety of the battery pack.
In the United States, General Motors run in several cities a training program for firefighters and first responders to demonstrate the sequence of tasks required to safely disable the Chevrolet Volt’s powertrain and its 12 volt electrical system, which controls its high-voltage components, and then proceed to extricate injured occupants. The Volt’s high-voltage system is designed to shut down automatically in the event of an airbag deployment, and to detect a loss of communication from an airbag control module. GM also made available an Emergency Response Guide for the 2011 Volt for use by emergency responders. The guide also describes methods of disabling the high voltage system and identifies cut zone information. Nissan also published a guide for first responders that details procedures for handling a damaged 2011 Leaf at the scene of an accident, including a manual high-voltage system shutdown, rather than the automatic process built-in the car’s safety systems. As of December 2011, no fires after a crash have been reported in the U.S. associated with the Volt, the Leaf or the Tesla Roadster.
As a result of a crashed tested Chevolet Volt that caught fire in June 2011 three weeks after the testing, the National Highway Traffic Safety Administration ( NHTSA) issued an statement saying that the agency does not believe the Volt or other electric vehicles are at a greater risk of fire than gasoline-powered vehicles. “In fact, all vehicles – both electric and gasoline-powered – have some risk of fire in the event of a serious crash.” The NHTSA announced in November 2011 that it was working with all automakers to develop postcrash procedures to keep occupants of electric vehicles and emergency personnel who respond to crash scenes safe. General Motors said the fire would have been avoided if GM’s protocols for deactivating the battery after the crash had been followed, and also stated that they “are working with other vehicle manufacturers, first responders, tow truck operators, and salvage associations with the goal of implementing industrywide protocols.”
In further testing of the Volt’s batteries carried out by NHTSA in November 2011, two of the three tests resulted in thermal events, including fire. Therefore the NHTSA opened a formal safety defect investigation on November 25, 2011, to examine the potential risks involved from intrusion damage to the battery in the Chevrolet Volt. As opposed to the Volt’s battery, the Nissan Leaf’s pack is shielded from damage by a layer of steel reinforcement. Also, Nissan clarified that the Nissan Leaf, unlike the Volt, has an air cooled battery pack that does not required to be depowered after a crash. The Leaf was designed with a battery safety systems that is activated in a crash that involves the airbags. The airbag control unit sends a signal mechanically to the battery and disconnects the high voltage from the vehicle. Both the Tesla Roadster and the Ford Focus Electric have liquid-cooling systems, and the Focus battery is enclosed in a steel case. After the initial Volt fire, the NHTSA examined the Leaf and other electric vehicles and said its testing “has not raised safety concerns about vehicles other than the Chevy Volt.”
On January 5, 2012, General Motors announced that it would offer a customer satisfaction program to provide modifications to the Chevrolet Volt to reduce the chance that the battery pack could catch fire days or weeks after a severe accident. General Motors explained the modifications will enhance the vehicle structure that surround the battery and the battery coolant system to improve battery protection after a severe crash. The safety enhancements consist of strengthen an existing portion of the Volt’s vehicle safety structure to further protect the battery pack in a severe side collision; add a sensor in the reservoir of the battery coolant system to monitor coolant levels; and add a tamper-resistant bracket to the top of the battery coolant reservoir to help prevent potential coolant overfill. On January 20, 2012, the NHTSA closed the Volt’s safety defect investigation related to post-crash fire risk. The agency concluded concluded that “no discernible defect trend exists” and also found that the modifications recently developed by General Motors are sufficient to reduce the potential for battery intrusion resulting from side impacts. The NHTSA also said that “based on the available data, NHTSA does not believe that Chevy Volts or other electric vehicles pose a greater risk of fire than gasoline-powered vehicles.” The agency also announced it has developed interim guidance to increase awareness and identify appropriate safety measures regarding electric vehicles for the emergency response community, law enforcement officers, tow truck operators, storage facilities and consumers.
All 12,400 Chevrolet Volts produced until December 2011, including all Amperas in stock at European dealerships, will receive the safety enhacements. Since production was halted during the holidays, the enhacements will be in place when production resumes in early 2012. Sales will continue and dealers will modified the Volts they have in stock, either before or after they are sold. General Motors sent a letter to Volt owners indicating that Chevrolet will contact them with more details about the service effort scheduled to begin in February 2012.
In December 2011, Fisker recalled the first 239 Karmas delivered to the U.S. due to a risk of battery fire caused by coolant leak. Of the 239 cars, less than fifty have been delivered to customers, the rest were in dealerships. In the report filed by Fisker Automotive with the NHTSA, the carmaker said some hose clamps were not properly positioned, which could allow a coolant leak and an electrical short could possibly occur if coolant enters the battery compartment, causing a thermal event within the battery, including a possible fire.
Great effort is taken to keep the mass of an electric vehicle as low as possible to improve its range and endurance. However, the weight and bulk of the batteries themselves usually makes an EV heavier than a comparable gasoline vehicle, reducing range and leading to longer braking distances; it also has less interior space. However, in a collision, the occupants of a heavy vehicle will, on average, suffer fewer and less serious injuries than the occupants of a lighter vehicle; therefore, the additional weight brings safety benefits despite having a negative effect on the car’s performance. An accident in a 2,000 lb (900 kg) vehicle will on average cause about 50% more injuries to its occupants than a 3,000 lb (1,400 kg) vehicle. In a single car accident, and for the other car in a two car accident, the increased mass causes an increase in accelerations and hence an increase in the severity of the accident. Some electric cars use low rolling resistance tires, which typically offer less grip than normal tires. Many electric cars have a small, light and fragile body, though, and therefore offer inadequate safety protection. The Insurance Institute for Highway Safety in America had condemned the use of low speed vehicles and “mini trucks,” referred to as neighborhood electric vehicles (NEVs) when powered by electric motors, on public roads.
Hazard to pedestrians
At low speeds, electric cars produced less roadway noise as compared to vehicles propelled by internal combustion engines. Blind people or the visually impaired consider the noise of combustion engines a helpful aid while crossing streets, hence electric cars and hybrids could pose an unexpected hazard. Tests have shown that this is a valid concern, as vehicles operating in electric mode can be particularly hard to hear below 20 mph (30 km/h) for all types of road users and not only the visually impaired. At higher speeds, the sound created by tire friction and the air displaced by the vehicle start to make sufficient audible noise.
The US Congress and the Government of Japan passed legislation to regulate the minimum level of sound for hybrids and plug-in electric vehicles when operating in electric mode, so that blind people and other pedestrians and cyclists can hear them coming and detect from which direction they are approaching. The Nissan Leaf is the first electric car to use Nissan’s Vehicle Sound for Pedestrians system, which includes one sound for forward motion and another for reverse.
Differences in controls
Presently most EV manufacturers do their best to emulate the driving experience as closely as possible to that of a car with a conventional automatic transmission that motorists are familiar with. Most models therefore have a PRNDL selector traditionally found in cars with automatic transmission despite the underlying mechanical differences. Push buttons are the easiest to implement as all modes are implemented through software on the vehicle’s controller.
Even though the motor may be permanently connected to the wheels through a fixed-ratio gear and no parking pawl may be present the modes “P” and “N” will still be provided on the selector. In this case the motor is disabled in “N” and an electrically actuated handbrake provides the “P” mode.
In some cars the motor will spin slowly to provide a small amount of creep in “D”, similar to a traditional automatic.
When the foot is lifted from the accelerator of an ICE, engine braking causes the car to slow. An EV would coast under these conditions, and applying mild regenerative braking instead provides a more familiar response. Selecting the L mode will increase this effect for sustained downhill driving, analogous to selecting a lower gear.
Cabin heating and cooling
Electric vehicles generate very little waste heat and resistance electric heat may have to be used to heat the interior of the vehicle if heat generated from battery charging/discharging can not be used to heat the interior.
While heating can be simply provided with an electric resistance heater, higher efficiency and integral cooling can be obtained with a reversible heat pump (this is currently implemented in the hybrid Toyota Prius). Positive Temperature Coefficient (PTC) junction cooling is also attractive for its simplicity — this kind of system is used for example in the Tesla Roadster.
Some electric cars, for example the Citroën Berlingo Electrique, use an auxiliary heating system (for example gasoline-fueled units manufactured by Webasto or Eberspächer) but sacrifice “green” and “Zero emissions” credentials. Cabin cooling can be augmented with solar power, most simply and effectively by inducting outside air to avoid extreme heat buildup when the vehicle is closed and parked in the sunlight (such cooling mechanisms are available as aftermarket kits for conventional vehicles). Two models of the 2010 Toyota Prius include this feature as an option.
Prototypes of 75 watt-hour/kilogram lithium-ion polymer battery. Newer lithium-ion cells can provide up to 130 W·h/kg and last through thousands of charging cycles.
Finding the economic balance of range against performance, energy density, and accumulator type versus cost challenges every EV manufacturer.
While most current highway-speed electric vehicle designs focus on lithium-ion and other lithium-based variants a variety of alternative batteries can also be used. Lithium based batteries are often chosen for their high power and energy density but have a limited shelf-life and cycle lifetime which can significantly increase the running costs of the vehicle. Variants such as Lithium iron phosphate and Lithium-titanate attempt to solve the durability issues with traditional lithium-ion batteries.
Other battery technologies include:
- Lead acid batteries are still the most used form of power for most of the electric vehicles used today. The initial construction costs are significantly lower than for other battery types, and while power output to weight is poorer than other designs, range and power can be easily added by increasing the number of batteries.
- NiCd – Largely superseded by NiMH
- Nickel metal hydride (NiMH)
- Nickel iron battery – Known for its comparatively long lifetime and low power density
Several battery technologies are also in development such as:
- Zinc-air battery
- Molten salt battery
- Zinc-bromine flow batteries or Vanadium redox batteries can be refilled, instead of recharged, saving time. The depleted electrolyte can be recharged at the point of exchange, or taken away to a remote station.
Travel range before recharging
The range of an electric car depends on the number and type of batteries used. The weight and type of vehicle, and the performance demands of the driver, also have an impact just as they do on the range of traditional vehicles. The range of an electric vehicle conversion depends on the battery type:
The Renault Fluence Z.E. will be the first electric car within the Better Place network, with sales scheduled to begin in Israel and Denmark by late 2011.
An alternative to quick recharging is to exchange the drained or nearly drained batteries (or battery range extender modules) with fully charged batteries, similar to how stagecoach horses were changed at coaching inns. Batteries could be leased or rented instead of bought, and then maintenance deferred to the leasing or rental company, and ensures availability.
Renault announced at the 2009 Frankfurt Motor Show that they have sponsored a network of charging stations and plug-in plug-out battery swap stations. Other vehicle manufacturers and companies are also investigating the possibility.
Replaceable batteries were used in the electric buses at the 2008 Summer Olympics.
Vehicle-to-grid: uploading and grid buffering
A Smart grid allows BEVs to provide power to the grid, specifically:
- During peak load periods, when the cost of electricity can be very high. These vehicles can then be recharged during off-peak hours at cheaper rates while helping to absorb excess night time generation. Here the batteries in the vehicles serve as a distributed storage system to buffer power.
- During blackouts, as an emergency backup supply.
Battery life should be considered when calculating the extended cost of ownership, as all batteries eventually wear out and must be replaced. The rate at which they expire depends on the type of battery technology and how they are used — many types of batteries are damaged by depleting them beyond a certain level. Lithium-ion batteries degrade faster when stored at higher temperatures.
The future of battery electric vehicles depends primarily upon the cost and availability of batteries with high specific energy, power density, and long life, as all other aspects such as motors, motor controllers, and chargers are fairly mature and cost-competitive with internal combustion engine components. Diarmuid O’Connell, VP of Business Development at Tesla Motors, estimates that by the year 2020 30% of the cars driving on the road will be battery electric or plug-in hybrid.
Nissan CEO Carlos Ghosn has predicted that one in 10 cars globally will run on battery power alone by 2020. Additionally a recent report claims that by 2020 electric cars and other green cars will take a third of the total of global car sales.
It is estimated that there are sufficient lithium reserves to power 4 billion electric cars.
Other methods of energy storage
Experimental supercapacitors and flywheel energy storage devices offer comparable storage capacity, faster charging, and lower volatility. They have the potential to overtake batteries as the preferred rechargeable storage for EVs. The FIA included their use in its sporting regulations of energy systems for Formula One race vehicles in 2007 (for supercapacitors) and 2009 (for flywheel energy storage devices).
Solar cars are electric cars that derive most or all of their electricity from built in solar panels. After the 2005 World Solar Challenge established that solar race cars could exceed highway speeds, the specifications were changed to provide for vehicles that with little modification could be used for transportation.
Charging station at Rio de Janeiro, Brazil. This station is run by Petrobras and uses solar energy.
Batteries in BEVs must be periodically recharged (see also Replacing, above).
Unlike vehicles powered by fossil fuels, BEVs are most commonly and conveniently charged from the power grid overnight at home, without the inconvenience of having to go to a filling station. Charging can also be done using a street or shop charging station.
The electricity on the grid is in turn generated from a variety of sources; such as coal, hydroelectricity, nuclear and others. Power sources such as roof top photovoltaic solar cell panels, micro hydro or wind may also be used and are promoted because of concerns regarding global warming.
Using regenerative braking, a feature which is present on many hybrid electric vehicles, approximately 20% of the energy usually lost in the brakes is recovered to recharge the batteries.
Smart ED charging from a Level 2 station
More electrical power to the car reduces charging time. Power is limited by the capacity of the grid connection, and, for level 1 and 2 charging, by the power rating of the car’s on-board charger. A normal household outlet is between 1.5 kW (in the US, Canada, Japan, and other countries with 110 volt supply) to 3 kW (in countries with 230V supply). The main connection to a house may sustain 10, 15 or even 20 kW in addition to “normal” domestic loads – though it would be unwise to use all the apparent capability – and special wiring can be installed to use this. As examples of on-board chargers, the Nissan Leaf at launch has a 3.3 kW charger and the Tesla Roadster appears to accept 16.8 kW (240V at 70A) from the Tesla Home Connector. These power numbers are small compared to the effective power delivery rate of an average petrol pump, about 5,000 kW. Even if the electrical supply power can be increased, most batteries do not accept charge at greater than their charge rate (“1C“), because high charge rates have an adverse effect on the discharge capacities of batteries. Despite these power limitations, plugging in to even the least-powerful conventional home outlet provides more than 15 kilowatt-hours of energy overnight, sufficient to propel most electric cars more than 70 kilometres (43 mi) (see Energy efficiency above).
Some types of batteries such as Lithium-titanate, LiFePO4 and even certain NiMH variants can be charged almost to their full capacity in 10–20 minutes. Fast charging requires very high currents often derived from a three-phase power supply. Careful charge management is required to prevent damage to the batteries through overcharging.
Most people do not usually require fast recharging because they have enough time, six to eight hours (depending on discharge level) during the work day or overnight at home to recharge. BEV drivers frequently prefer recharging at home, avoiding the inconvenience of visiting a public charging station.
In the UK, the electricity supply is generally 240 Volts, and a domestic current is generally supplied at 13A. This means that power is supplied to electric vehicles at around 3.1 kW and takes most available electric cars around 8 hours to fully charge. Soon electric vehicles will be able to accept higher currents, and charging times will be reduced (this is already the case for some models, such as the Tesla Roadster)
Hobbyists, conversions, and racing
The full electric Formula Student car of the Eindhoven University of Technology
Hobbyists often build their own EVs by converting existing production cars to run solely on electricity. There is a cottage industry supporting the conversion and construction of BEVs by hobbyists. Universities such as the University of California, Irvine even build their own custom electric or hybrid-electric cars from scratch.
Short-range battery electric vehicles can offer the hobbyist comfort, utility, and quickness, sacrificing only range. Short-range EVs may be built using high-performance lead–acid batteries, using about half the mass needed for a 100 to 130 km (60 to 80 mi) range. The result is a vehicle with about a 50 km (30 mi) range, which, when designed with appropriate weight distribution (40/60 front to rear), does not require power steering, offers exceptional acceleration in the lower end of its operating range, and is freeway capable and legal. But their EVs are expensive due to the higher cost for these higher-performance batteries. By including a manual transmission, short-range EVs can obtain both better performance and greater efficiency than the single-speed EVs developed by major manufacturers. Unlike the converted golf carts used for neighborhood electric vehicles, short-range EVs may be operated on typical suburban throughways (where 60–80 km/h / 35-50 mph speed limits are typical) and can keep up with traffic typical on such roads and the short “slow-lane” on-and-off segments of freeways common in suburban areas.
Faced with chronic fuel shortage on the Gaza Strip, Palestinian electrical engineer Waseem Othman al-Khozendar invented in 2008 a way to convert his car to run on 32 electric batteries. According to al-Khozendar, the batteries can be charged with US$2 worth of electricity to drive from 180 to 240 km (110 to 150 mi). After a 7-hour charge, the car should also be able to run up to a speed of 100 km/h (60 mph).
Japanese Professor Hiroshi Shimizu from Faculty of Environmental Information of the Keio University created an electric limousine: the Eliica (Electric Lithium-Ion Car) has eight wheels with electric 55 kW hub motors (8WD) with an output of 470 kW and zero emissions, a top speed of 370 km/h (230 mph), and a maximum range of 320 km (200 mi) provided by lithium-ion batteries. However, current models cost approximately US$300,000, about one third of which is the cost of the batteries.
In 2008, several Chinese manufacturers began marketing lithium iron phosphate (LiFePO4) batteries directly to hobbyists and vehicle conversion shops. These batteries offered much better power-to-weight ratios allowing vehicle conversions to typically achieve 75 to 150 mi (120 to 240 km) per charge. Prices gradually declined to approximately US$350 per kW·h by mid 2009. As the LiFePO4 cells feature life ratings of 3,000 cycles, compared to typical lead acid battery ratings of 300 cycles, the life expectancy of LiFePO4 cells is around 10 years. This has led to a resurgence in the number of vehicles converted by individuals. LiFePO4 cells do require more expensive battery management and charging systems than lead acid batteries.
Electric drag racing is a sport where electric vehicles start from standstill and attempt the highest possible speed over a short given distance. Organizations such as NEDRA keep track of records world wide using certified equipment.
Currently available electric cars
Norway has the largest electric car ownership per capita in the world. Shown a Tesla Roadster, a REVAi and a Th!nk City at a free parking and charging station in Oslo.
As of early 2012 the number of mass production highway-capable models available in the market is limited. Most electric vehicles in the world roads are low-speed, low-range neighborhood electric vehicles, led by the Global Electric Motorcars (GEM) vehicles, which as of December 2010 had sold more than 45,000 units worldwide since 1998. As of December 2011, the world’s top selling highway-capable electric cars are the Nissan Leaf, with more than 21,000 units sold worldwide through December 2011, and the Mitsubishi i-MiEV, with global cumulative sales of more than 17,000 units through October 2011. The i MiEV sales include units rebadged in France as Peugeot iOn and Citroën C-ZERO for sale in Europe.
The GEM neighborhood electric vehicle is the world’s top selling electric vehicle, with 45,000 units sold through 2010.
As of December 2011, Japan and the United States are the largest highway-capable electric car markets in the world, followed by several European countries. In Japan, more than 13,000 electric cars have been sold by November 2011, including more than 8,000 Leafs and 5,000 i-MiEVs. In the U.S. electric car sales are led by the Nissan Leaf with 9,693 units sold through December 2011. As of December 2011, Norway had 5,532 registered electric cars, the largest fleet of PEVs in Europe and the largest EV ownweship per capita in the world. A total of 5,579 electric vehicles were sold in China during 2011, including passenger and commercial vehicles.
A total of 2,240 cars were sold in Norway during 2011, up from 722 in 2010. Sales in 2011 were led by the Mitsubishi i-MiEV family with 1,477 electric cars including 1,050 i-MiEVs, 217 Peugeot iOns and 210 Citroën C-Zeros. A total of 2,630 electric cars were registered in France in 2011, up from 184 units in 2010. Also during 2010, around 1,200 non highway-capable PEVs were sold in the French market, including 406 heavy quadricycles and 796 utility vehicles. Sales in the French market for 2011 were led by the Citroën C-Zero with 645 units followed by the Peugeot iOns with 639 vehicles, and the Bolloré Blue Car with 399 electric cars. Germany had 2,307 electric car registered by January 1, 2011, and a total of 1,808 vehicles were sold through November 2011. Since 2006 a total of 1,096 electric cars have been registered in the U.K. through December 2010, and a total of 1,082 units were sold during 2011, up from 138 units in 2010. A total of 314 electric cars have been registered in Spain through November 2011, 314 in Austria, 283 in Denmark, 269 in the Netherlands, 111 in Sweden and 103 in Italy through June 2011.
Nissan Leaf at a designated parking space reserved for electric cars
There are also several pre-production models and plug-in conversions of existing internal combustion engine models undergoing field trials or are part of demonstration programs, such as the BMW ActiveE, Volvo C30 DRIVe Electric, Ford Focus Electric, and the RAV4 EV second generation.