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Ford Europe e-Ka electric car
Automakers like Ford have learned that fuel cell vehicles need advanced batteries. Pictured is Ford Europe's battery electric e-Ka powered by lithium batteries.

Advanced Batteries Find New Roles

Technology perpective from the president and CEO of Lithium Technology Corporation

By David Cade

Over the past year much media attention has been devoted to fuel cells as a new, environmentally friendly, "energy independence" power source for automobiles, replacing the fossil-fuel based internal combustion engine which has been the principal propulsion source in cars for over a century.

To a casual observer, the impression created by all this attention is that widespread commercial deployment of fuel cell-powered automobiles is just around the corner. Nothing could be further from the truth.

Many technical, logistical and economic challenges must be mastered before this happens. In fact, most industry experts now place the actual mass-market introduction of automobile fuel cells somewhere between 10 and 20 years. In addition, all of the hype regarding fuel cells, coming on top of the growing publicity being accorded to Hybrid Electric Vehicles (HEVs), has caused some confusion among consumers. This article is intended to clarify the picture.

The Freedom CAR Initiative
The Bush Administration is indeed putting more emphasis on the development of fuel cells, while still providing incentives for HEVs. The Department of Energy (DOE) FY 2003 budget proposes creation of a national infrastructure that would make hydrogen fuel cell-powered vehicles feasible. The new program, to be called Freedom Cooperative Automotive Research, or Freedom Car, is aimed at eliminating passenger cars and trucks as a source of pollution and greenhouse gasses. The DOE budget proposes that consumers receive up to $8,000 in credit toward the purchase of a fuel cell-powered vehicle.

Freedom Car would replace the Partnership for a New Generation of Vehicles (PNGV) program, a consortium including the DOE and the U.S. "Big Three" automakers, on which the federal government has spent $1.5 billion since its inception in 1994. The PNGV emphasis was on creating an 80mpg super car through the use of today's HEV technology, which combines a small gasoline engine and a battery powered electric motor to achieve dramatically improved fuel consumption performance.

While U.S. auto manufacturers say they still can't build an affordable HEV that meets the PNGV target, the gasoline-electric hybrid is rapidly gaining market acceptance with consumers. Toyota and Honda together have sold over 100,000 HEVs since their introduction in 1997, and are now planning to introduce other new gasoline-electric hybrid models. Honda has announced that it will produce 24,000 hybrid Civic sedans annually beginning this year. Toyota has indicated that it intends to begin manufacturing a hybrid SUV, and that over the next five years it wants to put 300,000 new HEVs on the road.

Other automakers are also beginning to jump on the HEV bandwagon. Ford Motor has announced plans to introduce a gasoline-electric hybrid version of the Escape SUV by the end of 2003. Ford is touting this as a "mass market vehicle" (tens of thousands per year), which will deliver 40mpg in city driving but carry a 25% price premium over the conventional gasoline powered Escape. Daimler-Chrysler plans to sell a hybrid version of its Dodge Ram pickup truck beginning in the 2005 model year and GMC says it intends to produce full size hybrid trucks by 2004. The marketing firm J.D. Powers & Associates recently released a study in which 60% of U.S. car buyers surveyed said they would seriously consider buying a hybrid vehicle. Reasons given are fuel economy, environmental friendliness and reduced dependence on foreign oil.

These HEVs all have or will have battery systems ranging from 144-288 volts (compared to today's standard 12 volt car battery), which power the car part of the time in tandem with the small gas engine. The result is a "half electric" vehicle which can increase fuel economy from 15% to 50% or higher over comparable conventional vehicles thereby reducing emissions. Innovative transmission systems assure a smooth blending of the two power sources. The gas engine powers the vehicle while cruising on level roads and charges the on-board battery which provides the extra power needed for acceleration and climbing hills. There is no need to stop frequently for lengthy charges as for fully Electric Vehicles, which may never become sufficiently practical for widespread commercial use.

Although the PNGV program has been superseded, there still are incentives for automakers to develop -- and for consumers to buy -- HEVs. The 2003 DOE budget includes a tax credit of up to $4,000 towards the purchase of an HEV. Moreover, with the notable market success of the Toyota Prius and the Honda Insight HEVs, and increasing demands for more "on board" power, there is growing interest on the part of automakers to apply advanced battery technology to a variety of automotive applications.

The 42-Volt Battery Revolution
While HEVs continue to get the lion's share of publicity, there is another application that is quietly making its way to the showroom floor -- 42-volt battery systems. The 12-volt battery, which has been around for 45 years, cannot accommodate all the new electronic gadgetry available for today's cars. In the mid 90's carmakers in the U.S., Japan and Europe began looking at tripling the on-board battery power to 36 volts, which increases to 42 volts when the car is operating.

Engineers quickly realized that this increase in electric power could also be used to replace mechanical and hydraulic systems with their inefficient belt drives. This increased use of electronic power for such functions as steering and fuel pumping/metering could provide at least a 10 percent improvement in fuel economy, and conceivably reach 20 percent by use of such HEV features as "stop-start" which shuts off the engine power during prolonged stops.

The 42-volt systems would provide multiple advantages -- better fuel efficiency, reduced emissions and more consumer benefits by enabling an expanded array of on-board electronics and creature comforts, some of which operate when the vehicle is not in use. Hence the auto industry now refers to 42-volt systems as "soft" or "mild" hybrids, offering less fuel economy than the higher voltage "full" HEVs, but at less initial cost. The 42-volt systems involve some redesign and modification of the electrical system and its components (particularly lights) although some manufacturers are initially planning to use a 12-volt battery along with the 42-volt battery until the older system can be phased out.

At the outset, the extra cost to consumers for a 42-volt system is expected to be about $1,000. Japanese 42-volt systems are anticipated in the marketplace in 2003, while European manufacturers are aiming at 2004-5 for the introduction. In Europe, the 42-volt initiative has been folded into the ASTOR project to assess and test advanced energy storage systems under the auspices of EUCAR, a consortium of European automakers. The intention of U.S. auto manufacturers regarding 42-volt systems is less clear. In any case, market projections for 42-volt systems over the next ten years range from 12-30% of all new cars sold.

At this juncture, all automakers are faced with critical decisions on whether to introduce 42-volt systems or the higher voltage HEV systems for particular models. However, even if the decision is for an HEV, it is possible that those vehicles would still use a 42-volt battery to power the accessories, freeing up the higher volt HEV battery for propulsion sharing functions. In fact, within the auto industry there are several levels of 42-volt/HEV architectural requirements, depending on the number of functions added to the mix and the decision regarding the most efficient power sources. Thus it is virtually certain that there will not be a single commercial solution or configuration embraced by the global auto industry.

The raising of fuel efficiency standards on internal combustion engines is being touted by environmentalists, but is not being embraced by the auto manufacturers. Indeed, the best way to achieve fuel efficiencies may be to follow where impressive market inroads seem to be heading already -- 42-volt "mild" hybrids and HEVs. Moreover, this more realistic approach has the added advantage of reducing the dependence on Middle East oil, which could become increasingly important given the likelihood of continuing turmoil in that part of the world.

Fuel Cells Go Better with Batteries
Automobile fuel cells running on compressed hydrogen would meet the promise of zero emissions from the vehicle itself. However, as stated previously, there are many issues to be resolved before fuel cell-powered vehicles sit in our driveways. Besides developing a vehicle that compares with the sticker price, driving range and reliability of gasoline powered vehicles, fuel cell-powered vehicles will require a new fuel infrastructure to be viable.

There are three basic infrastructure models under consideration:

The first two options are not very "consumer friendly" in terms of ease of operations and the time required to "fill up", and are not very "supplier friendly" either because today's gas stations would require significant modifications. The third option, an on-board "reformer", has the advantage of staying with a liquid hydrocarbon fuel that can be pumped into the gas tank in the same way as gasoline fuel is today. However, it should be noted that in doing their job, "reformers" will produce some greenhouse gas emissions.

Regardless of which infrastructure model is eventually selected, adding a high performance battery to the fuel cell-powered vehicle will allow it to capture energy from regenerative braking and thus increase the efficiency of the fuel cell just as it does for the small internal combustion engine of today's HEV.

Moreover, in the case of the most viable economic option, an on- board "reformer", the increased fuel economy afforded by the fuel cell-battery hybrid would actually decrease the pollution generated by the vehicle during the on-board production of the hydrogen fuel. As a matter of fact, the PNGV came to the conclusion that high performance batteries are a critical enabling technology for automobile fuel cells.

Many of the major automakers are building and testing fuel cell vehicle prototypes -- with and without hybrid battery systems. For example, Toyota is experimenting with a series of Fuel Cell Hybrid Vehicles (FCHVs) that use a variety of fuels and different methods to store these fuels. One of these prototypes, which Toyota calls the FCHV-4, incorporates a battery along with the fuel cell. No doubt in designing the FCHV-4, Toyota has incorporated what it has learned about improved fuel efficiency from the Prius and its other HEV platforms. Ford is developing an FCHV version of its Focus sedan, and has stated that the fuel cell-battery combination results in a 25% improvement of overall fuel economy. .

The new Freedom Car initiative supports the development of a fuel distribution infrastructure for hydrogen-powered fuel cell vehicles, without specifying a particular option. But whatever the outcome, it is clear that HEV technology will contribute to improving fuel economy with any future hydrogen-based fuel supply.

Advanced Batteries Are Key
From the standpoint of the global auto industry, there clearly are different camps regarding advanced battery technology. U.S. carmakers generally believe there is little justification for introducing new battery technology unless they can do it in all of their models and can show that the annual fuel savings will offset the added cost of the advanced battery.

The Europeans look at it differently: more powerful batteries can provide added value in terms of creature comforts on select high-end models. In addition, the fuel savings aspect is viewed much more importantly because of the higher cost of gasoline in Europe, and consumers are much more attuned to environmental factors. The Japanese are much more focused and pragmatic -- they are just "doing it" without debating the merits or cost, and simply judging consumer acceptance.

Thus, advanced high-performance batteries are the key enabling technology for gasoline- electric HEVs as well as for fuel cell-electric hybrids (FCHVs). So let's examine the various battery technologies available for these platforms by comparing and contrasting their cost, performance, size and weight factors.

The global market for rechargeable batteries can be split into two major sectors -- one for portable electronics and another for larger applications such as automotive. Batteries for portable electronics were dominated by sealed lead acid and nickel cadmium technologies until about 1991. Nickel metal hydride and lithium ion technologies developed as demand for lighter weight, smaller and more powerful batteries grew in this market sector. Today, for commodity items such as cell phones, PDAs and notebook computers, the higher energy density lithium ion technology has overtaken nickel metal hydride in sales, due to decreasing material costs and decreasing manufacturing costs for lithium ion.

A similar progression in battery technology has begun for automotive battery applications. Automotive batteries have been dominated by lead acid technology for over 100 years. However, increasing demand for better performance -- particularly improved life cycle and operation over a broad temperature range -- has driven the development of advanced high performance battery technologies. The market has first turned to nickel metal hydride, which provides improved cycle life over lead acid. Lithium ion systems, which are expected to enter this market in the near future, also provide improved cycle life under pulsing or under deep discharge when compared to lead acid. Moreover, lithium ion technology provides higher energy density and generally outperforms nickel metal hydride at high and low application temperatures.

Nevertheless, displacing the low cost, lead acid technology will take time. In part, this is due to recent advances with Sealed Lead Acid (SLA) or Valve Regulated Lead Acid (VLRA) battery technology that has improved cycling capability over its predecessor, flooded lead acid technology. This strong starting position of lead acid is being countered by a growing awareness of the higher life cycle cost of lead acid batteries. Considering the replacement and maintenance cost of batteries over the life of an automobile or a stationary distributed power unit tips the balance to nickel metal hydride and the more robust lithium ion technology.

Some market studies predict that nickel metal hydride will replace lead acid technology in the advanced automotive battery market. Nickel metal hydride technology has in fact penetrated this market with the Toyota Prius and Honda Insight HEVs and is expected to follow suit in 42-volt automotive systems. After entering the marketplace, lithium ion should compete more than favorably with nickel metal hydride in cost, size, weight, and performance. The active materials in nickel metal hydride batteries are inherently expensive, while new materials for lithium ion continue to decrease in cost while giving improved performance. Also, batteries with lithium ion chemistry require fewer cells to reach system voltage -- an important factor that simplifies battery assembly, increases energy density and improves high power performance.

In the final analysis, there are two key performance measures when comparing the principal battery chemistries for automotive applications -- power and calendar life. The chart below provides a general comparison of these two key factors as well as other important requirements for batteries in advanced automotive applications such as 42V and HEV systems. The numbers represent averages of available performance data.

Battery Type

Specific Power

W/kg

Specific Energy

Wh/kg

Operating Temperature

oC

Calendar Life

[In Vehicle

Years]

Sealed Lead Acid

600

40

-20 to +70

2

Nickel Cadmium

300

45

-20 to +45

3

Nickel Metal Hydride

400

65

-10 to +45

5

Lithium Ion Polymer

500

150

-20 to +60

5

Lithium Ion Liquid

600

130

-30 to +80

8

Considering the broadest set of conditions and requirements -- high/low temperature performance, high energy or high power, and long calendar life -- lithium ion is developing into the most cost effective battery solution for advanced automotive applications.

This conclusion is true for both general types of lithium ion technologies -- lithium ion liquid and lithium ion polymer. Lithium ion liquid technology is simpler to manufacture and has been proven on a large commercial scale in portable electronics applications. These have been produced as small cylindrical or small wound prismatic cells. Lithium ion polymer has also been proven commercially in portable electronics, but only in a few selected applications where the ultrathin form factor adds premium value. However, lithium ion polymer has been more difficult and costly to manufacture and has tended not to work well in applications requiring high power density or high/low temperature operations. Lithium ion liquid also provides the best combination of power and calendar life, the most critical requirements for advanced automotive systems.

Lithium ion liquid therefore appears to offer a quicker route to market and a better solution for automotive applications. Advances in manufacturing technology by Lithium Technology Corporation (LTC) have resulted in the development of thin, flat lithium ion liquid cells which can be stacked and which heretofore have been the exclusive form factor domain of lithium ion polymer. This technology is being extended to large footprint lithium ion liquid cell stacks for automotive applications.

The automotive battery market segment requires customized, tailored solutions for each application by each auto manufacturer. This is totally different than for the portable electronics market segment, which has been driven by very inexpensive, standardized commodity products from the Pacific Rim. Since 1997, LTC has been developing and evaluating a wide range of lithium ion cell designs and large battery assemblies (complete with battery management and control systems) to cover the full spectrum of automotive applications. We are working with selected automotive OEMs on specific product requirements to leverage our large battery know-how and expertise in entering this rapidly growing market segment.

We have in fact already produced a 144-volt HEV prototype battery, and together with our German lithium-polymer battery company partner, GAIA, expect to deliver our first 42-volt prototype battery to a major German automobile manufacturer in the second quarter of 2002.

From our perspective, we have a very firm conviction that lithium-based rechargeable batteries will be a key component of automotive power plants and operations for the foreseeable future -- certainly for the next two decades at the very least.

Times Article Viewed: 4252
Published: 14-Apr-2002

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