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Batteries for Electric Cars

Batteries for Electric Cars

The Electric Car Places Heavy Demands on its Batteries

Whether making an electric car from an existing fueled vehicle or developing a new model, the batteries of electric cars should have the following characteristics:

1) Store as much energy as possible in a given volume to achieve a long operating range.
2) Have the lowest weight possible to reduce the load on the drive system.
3) Recharge rapidly and easily.
4) Perform well through many charge/discharge cycles over the life of the vehicle.

For an amateur builder converting a standard internal combustion gasoline-powered automobile, nickel-zinc batteries may offer attractive features. They are less expensive than lithium-ion batteries of comparable size. Their energy density is about 70 watt-hours per kilogram, compared to 150 or more for Lithium-ion. On the other hand, they are easier to charge, accepting either a constant voltage charging system or a constant current charge, with little overcharge required. The metals used in the nickel-zinc battery do not present a hazardous waste disposal problem when the battery needs to be replaced, and there is no lithium present that could cause a fire in case of an accident.

See the PowerGenix Company for more information on nickel-zinc batteries.

The race is on to bring an electric auto to market

The automobile manufacturers realize that the time to develop an electric automobile is now. Ecological pressure is on to move away from hydrocarbon-fueled vehicles including bio-diesel and methanol derived from the fermentation of grain or biomass. Although the latter fuels may be considered renewable resources, they still produce carbon dioxide when burned, contributing to global warming. Electric vehicles may be charged using energy produced by hydro-electric and wind power or other sources of non-polluting electricity such as thermal power and wave and tidal power from the oceans.

In searching for the best batteries to store energy to drive these vehicles, carmakers want to provide a long-range operation between recharges. The goal is to store many kilowatt-hours of energy in the smallest, lightest, and least costly package. It is necessary to store about 35 kilowatt-hours in a battery to drive a small car for more than 100 miles. Lithium-ion batteries have been chosen by most automakers for their vehicles, except in the case of hybrid vehicles, where there is an internal combustion engine to supply long-distance driving energy. In hybrid vehicles such as those made by Hyundai Motors, a smaller lithium-polymer battery supplies about 1.5 kilowatt-hours, sufficient to drive the car for only a limited number of miles, but it is backed up by an efficient 2.4-liter gasoline engine. The Hyundai Sonata hybrid was announced at the 2008 Los Angeles Auto Show in November, 2008.

Comparison of battery types

Four figures help choose which battery type is best for a given application: The energy/weight ratio, the energy/volume ratio, the power to weight ratio, and the cost in watt-hours per dollar. In comparison to the common lead-acid battery, which is probably the least desirable to run an electric vehicle, the numbers are

Lead-acid 30-40 60-75 180 4-10
NIckel-Zinc 60-70 170 900 2-3
Lithium-Ion 160 270 1800 3-5
Lithium-Polymer 130-200 300 to 2800 3-5

Two other values should also be considered, the self-discharge rate, which causes the charge to diminish over time, and the cycle life of the batteries, the number of times the batteries can undergo a deep discharge and still accept charge. The batteries listed above perform well in those categories.

New partnerships announced

Beginning in the fall of 2008 and continuing into 2009, many companies announced partnerships to develop electric automobiles. Some of these are listed below.

Hyundai (Korea) and LG Chem (Korea) for the development of a lithium polymer battery to power hybrids and electric vehicles.

Hyundai (Korea) and the California Fuel Cell Partnership (since 2000)
Hyundai (Korea) and Chevron Corp. and UTC Power — fleet vehicle testing program (2004)

BMW Group (Europe) launches the MINI E with 204-HP Li-Ion Battery Pack (battery manufacturer and controller not specified, but probably Johnson Controls-Saft(US-France). Battery consists of 5,088 cells grouped into 48 modules, supplying a nominal 380 volts d-c.) Announced in Oct. 2008.

General Motors, Vauxhall, Samsung, and Bosch

Ford Motor Co. and Johnson Controls-Saft (joint US-France venture) for a plug-in hybrid auto in 2012 and an all-electric small car in 2011.

Johnson Controls-Saft and Maxwell Technologies for a process to coat lithium electrodes for lithium-ion batteries for hybrid vehicles.

General Motors and LG Chem (Korea) for the batteries for the GM Volt.

Toyota (Japan) and Pansonic EV (Japan) for hybrid batteries

Ford Motor Co. and Magna International (Canada)
Ford Motor Co. and California Edison
Ford Motor Co. and Changan Auto Group (China)
Ford Motor Co. and Tanfield (UK)

Mitsubishi Motors (Japan) and Pacific Gas And Electric

See Also

Tesla Motors (US) and Daimler AG

Better Place Mobility Group (Palo Alto, CA – includes Renault and Nissan), with Province of Ontario (Canada), Bullfrog Power(Canada) and Macquarie Group (Canada, banking)

Better Place Mobility Group with the State of California, Israel, Denmark, and Australia

LG Chem (Korea) and ST Microelectronics for a battery management package to balance up to 1600 volts worth of cells

Nissan (Japan) and NEC (Japan) to form Automotive Energy Supply Corporation making Lithium-ion batteries

A plug-in doesn’t mean a free fill-up

Some of the prices you used to pay at the pump will be reflected in your electric utility bill if you plug in your new electric car to recharge it at home. Consider that a small car like the MINI E from the BMW Group will need about 30 kilowatt-hours of electricity to go 150 miles (240 km). Depending on the electricity rates where you live, which may vary from 7 to 18 cents per kilowatt-hour, this may cost between $2.10 to $5.40. Although this compares favorably with about $9 spent at the gas pump for an equivalent trip, the cost may change when a way is found to add in what used to be collected as a gas tax at the pumps. Do you have any idea how much it costs annually to mow the grass on a section of the Interstate, or light a traffic interchange for a year? Right now, electricity costs are high in the Northeast United States and California, but low where there is an abundant supply of hydro-electric power. However, this may change when the utilities find that it is necessary to rebuild their power grids to handle the increased demands of charging electric vehicles.

Here are some related articles on other pages of the All About Batteries web site:

Lithium-Metal-Polymer batteries for electric vehicles

Maxwell Technologies Ultracapacitors for ultracapacitors to provide long cycle life and high peak currents in fuel-cell, hybrid, and electric cars.

Zinc-Air batteries for electric vehicles.

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