Electric Vehicle Battery University

6 Апр 2014 | Author: | Комментарии к записи Electric Vehicle Battery University отключены
BAIC E150 EV Electric Cars

Electric Vehicle

Cars with electric powertrains have been around for more than 100 years. At the turn of the century, a car buyer had three choices of propulsion system: electric, steam, and internal combustion (IC) engine, of which the IC engine was the least common.

The electric cars appealed to the upper class and the vehicles were finished with fancy interiors and expensive materials. Although they were higher in price than the steam and gasoline-powered vehicles, the wealthy chose the electric car for its quiet and comfortable ride over the vibration, smell and high maintenance of gasoline-powered counterpart. Best of all, the electric vehicle (EV) did not require changing gears.

Back then, the knuckle busting, wrist-wrenching chore of shifting gears was the most dreaded task for driving a gasoline-powered car. Nor did the EV need manual cranking to start the motor, a task the upper class did not want to be seen doing. Since the only good roads were in town, the limited range of the EV was no problem, and most of the driving was local commuting.

Production of the EV peaked in 1912 and continued until the 1920s.

The battery of choice for the EV was lead acid. For an added fee, the buyer could fit the Detroit Electric with a nickel-iron (NiFe) battery, a technology Thomas Edison promoted. NiFe had a cell voltage of 1.2V, was robust and could endure overcharging and repeated full discharging. Being a good businessman, Edison continued to promote NiFe over lead acid by boasting its good performance at subfreezing and hot temperatures. Then in 1914, a devastating fire destroyed the Edison factory and the popularity for this battery began to decline.

On a purely technological level, NiFe provided only a slightly better specific energy to lead acid and was expensive to manufacture. In addition, the battery performed poorly at low temperatures and the self-discharge was 2040 percent a month, considerably higher than lead acid.

The Detroit Electric, one of the most popular EVs then, was said to get 130km (80 miles) between battery charges. Its top speed was 32km/h (20mph), a pace considered adequate for driving. Physicians and women were the main buyers.

Thomas Edison, John D. Rockefeller, Jr. and Clara Ford, the wife of Henry Ford, drove Detroit Electrics. Figure 1 shows Thomas Edison with his 1914 Detroit Electric model.

Figure 1:

Thomas Edison with a 1914 Detroit Electric, model 47

Thomas Edison felt that nickel-iron was superior to lead acid for the EV and promoted his more expensive batteries.

Courtesy of National Museum of American History

Henry Ford’s mass-production and cost-cutting measures in 1912 were not the only reason for the shift towards gasoline-powered cars. The invention of the starter motor, the need to travel longer distances, and the discovery of Texas crude oil made the IC engine more attractive and affordable to the general public.

The EV became a thing of the past until the early 1990s when the California Air Resources Board (CARB) began pushing for more fuel-efficient and lower-emission vehicles. It was the CARB zero-emission policy that prompted General Motors to produce the EV1. Available for lease between 19961999, the EV1 initially ran on an 18kWh lead acid battery.

The lead acid was later replaced with a 26kWh NiMH pack. Although the NiMH gave an impressive driving range of 260km (160 miles), the EV1 was not without problems. Manufacturing costs rose to three times the cost of a regular gasoline-powered car, and in 2001 politicians changed the CARB requirements, which prompted General Motors to withdraw the EV1, to the dismay of many owners.

The 2006 documentary film Who Killed the Electric Car? gives a mixed impression of government-initiated programs for cleaner transportation.

To match the range of an IC-powered vehicle, the EV needs a battery capable of delivering 2540kWh. This is twice the battery size of a PHEV and 10 times that of the HEV. The electro-chemical battery is not the only expense added to the EV; the power electronics to manage the battery make up a large part of the vehicle cost.

An EV without a battery is roughly the same cost as a traditional gasoline-powered car. Figure 2 shows the battery of the Nissan Leaf as part of the under-chassis installation.

Figure 2: Cutaway battery of Nissan Leaf electric vehicle. The Leaf includes a 24kWh lithium-ion battery with a city driving range of 160km (100 miles). The battery fits under the floor of the car, weighs 272kg (600lb) and is estimated to cost $15,600 (2010).

Courtesy of Nissan Motors

A valid concern with the EV is the limited driving range, especially in cold and hot weather. Designed to go 160km (100 miles) on a charge, a BMW Mini E traveled about half that distance in cold weather before running out of power. Additional energy is drawn to heat the cabin and battery performance drops in cold temperatures. While thermal technologies are making advances, achieving a comfortable cabin environment remains an issue with most EV designs.

To conserve energy, EV drivers use the heat and air-conditioning sparingly and drive in a reasonable manner.

The Mini E takes 68 hours to fully charge the battery on a regular 115VAC outlet. High-power outlets (220240VAC) can reduce the charge time to 35 hours, and high-power public fill-up stations can charge a battery in two hours. In most cases it’s the available electrical outlet and not the battery that governs charge times. Charging a 40kWh battery in six minutes, as some battery manufacturers might claim possible, would require 400kW of power.

An ordinary 115VAC electrical outlet provides only 1.5kW, and a 230VAC, 40A kitchen stove outlet delivers 9kW. (The electric kitchen stove is often the household appliance that draws the most power. It feeds off a 230VAC, 40-ampere circuit.)

BAIC E150 EV Electric Cars

Car manufacturer Tesla Motors focuses on building EVs that generate zero emissions with very high performance. Its electric Roadster boasts a zero-to-96km (zero-to-60 mp) acceleration of 3.9 seconds. The 7,000 Li-ion cells store 53kWh of electrical power and deliver a driving range of 320km (200 miles). Liquid cooling prevents the cells from exceeding 35C (95F).

To achieve the five-year warranty, Tesla charges the Li-cobalt cells to only 4.10V instead of 4.20V/cell. The electronics circuits inhibit charging at freezing temperatures. At $130,000, this car turns heads and becomes a discussion item, however, the $40,000 cost of a replacement battery could cause concern for long-term Tesla owners.

A battery for the electric powertrain currently costs between $1,000 and $1,200 per kWh. According to The Boston Consulting Group (BCG), relief is in sight. BCG claims that the price of Li-ion will fall to $750 per kWh within the next decade. Meanwhile, batteries for consumer electronics are only US$250400 per kWh.


High volume, automated manufacturing, lower safety requirements and shorter calendar life make this low price possible. BCG predicts that Li-ion batteries for the powertrain will eventually match these consumer prices, and the cost of a 15kWh battery will drop to about $6,000 from $16,000.

The largest decrease in battery prices is expected to occur between now and 2020, with a more gradual decline thereafter. According to BCG, the anticipated calendar life of the battery will be 1015 years. E-One Moli Energy, a manufacturer of lithium-ion cells for power tools and electric vehicles, points out that the cost of Li-ion can be reduced to $400 per kWh in high volume, however, the peripheral electronics managing the battery, including heating and cooling, will remain high, essentially doubling the price of a pack. Reductions are also possible here, and E-One Moli Energy predicts that the electronics will only make up 20 percent of the cost of an EV battery in five years. These forecasts are speculative, and other analysts express concern that the carmakers may not be able to achieve the long-term cost target without a major breakthrough in battery technology.

They say that the current battery cost is 3 to 5 times too high to appeal to the consumer market.

On the surface, driving on electricity is cheaper than burning gasoline but today’s low fuel prices, uncertainty about the battery’s service life, along with unknown abuse tolerances and high replacement costs, will reduce the incentive for buyers to switch from a proven concept to an electric vehicle. If a driver wants the 500km range between fill-ups that is achievable with a gasoline-powered car,the battery would need a capacity of 75kWh according to Technology Roadmaps Electric and Plug-in Hybrid Electric Vehicles (EV/PHEV). At an estimated $400 price tag per kWh, such a battery would cost over $30,000 and weigh nearly a ton.

Technology Roadmap compares the energy consumption and cost of gasoline versus electric propulsion as follows: An EV requires between 150 and 200Wh per km depending on speed and terrain. At a consumption of 200Wh/km and an electricity price of $0.15 per kWh, the energy cost to drive an EV translates to $0.03 per km. This compares to $0.06 per km for an equal-size gasoline-powered car and $0.05 per km for diesel.

The price estimations exclude equipment costs, service and eventual replacement of the battery and IC engine.

To prepare for the EV market, researchers and battery manufacturers have invested significant resources to develop better battery technologies, and many are taking advantage of generous government incentives. But there is a danger. For the sake of optimal specific energy, some start-up companies are experimenting with aggressive design concepts using volatile chemicals that compromise safety.

They may push the envelope by announcing impressive advances, emphasizing only the pros and squelching the cons. Such behavior will get media attention and entice venture capitalists to invest, however, hype contributes little in finding a solution that will improve existing battery technologies.

The battery will determine the success of the EV, and until improvements are achieved in terms of higher specific energy, longer service life and lower cost, the electric powertrain may be limited to a niche market. While governments spend large sums in the hope of improving current battery technologies, we must realize that the electrochemical battery has limitations. This was made evident when motorists tested eight current and future models with electric powertrains and attained driving ranges that were one-third less than estimated.

Table 3 lists a rundown of range and charge times. The electric cars were tested in real-life conditions on highways, over mountain passes and under winter conditions in 2010.

Electric vehicle

BAIC E150 EV Electric Cars

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