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BATTERIES FOR ELECTRIC VEHICLES
Background. The 1995 BTAP assessment found that several advanced
battery types with the potential to meet the mid-term performance and
cost targets of the United States Advanced Battery Consortium (USABC)
had reached the pre-prototype stage. That Panel also concluded that
even the leading candidates among these were unlikely to be commercially
available before 20002001, and this only in a complete success scenar
Io that required, in particular, firm commitments to battery production
plants no later than 19989~99。In the absence of historic precedent,
the 1995 BTAP study had to leave open the question of whether
availability of batteries meeting or, at least, coming close to USABC
mid-term targets would lead to successful commercialization of electric
vehicles (EVs). The study??s battery- cost survey indicated [(1), Table
II.4] that the costs of the batteries being developed were likely to
be well above USABC mid-term targets, except possibly in large-scale
production, adding to the uncertainty about the prospects of EVs.
Over the past five years, battery developers and automobile
manufacturers devoted large efforts to the continued advancement of
EV-battery technology and the development of a new generation of
electric vehicles. Under the MoA between the six leading automobile
manufacturers and the California Air Resources Board, a substantial
number of these vehicles has been deployed. Nevertheless, since they
are produced in limited volume only, the vehicles??including their
batteries??are expensive, and vehicle leases had to be subsidized
heavily to attract early users. As the time approaches for critical
decision on actions needed to implement the current ZEV provisions,
the question again arises whether batteries with the required
performance and cost characteristics could be available in time for
commercialization of broadly marketable EVs by 2003. The most important
requirements that must be met by EV batteries are re-examined below
from today??s perspective, and they are used in Section II.2 to identify
the candidate EV batteries that were examined more closely by BATTERY
TARGETSREQUIREMENTS

A technical team drawn primarily from the major U.S. automobile
manufacturers derived the long-term battery targets in Table II.1
nearly a decade ago from the postulate that, to be competitive, an EV
intended for the same purpose as an internal combustion engine
(ICE)-powered vehicle had to match that vehicle with respect
to all key characteristics: performance, durability, safety,
convenience and cost. The target ICE vehicle assumed in that derivation
was a mass-produced (45-passenger) family sedan with characteristics
similar to the Chevrolet Lumina, Ford Taurus or Chrysler Concorde.
Recognizing the difficulty of emerging EV-battery technology meeting

the very demanding long-term targets, USABC also defined a less severe
set of near- term targets (see Table II.1) for the batteries of EVs that
might find limited applications. Recently, USABC defined a set of
battery ?°Commercialization?± targets that, if met, should permit EVs
to begin entering the market. As shown in Table II.1, the
commercialization targets for performance fall generally between
the near and long-term values. The commercialization targets for
cycle and calendar life are as demanding as the long-term values, while
the cost target is relaxed to the near-term value of $$150kWh. The most
important requirements for EV batteries are reviewed below from
today??s perspective and compared to the USABC targets.

1.1. Performance
Specific Energy. As shown in Appendix C, today??s state-of-the-art
45-passenger vehicles (Table C.1) have practical ranges of about
75-100 miles (Table C.2, lines 4B and 4C) with 29-32 kWh batteries.
These batteries weigh between 450kg (NiMH) and 360kg (Li Ion), and they
represent approximately 30% and 20%, respectively, of vehicle curb
weights. The specific energy of the NiMH batteries used varies from
about 50 to 64 Whkg; it is nearly 90 Whkg for the Li Ion battery.
Utility vehicles and vans (see Table C.1) attain about 65-85 miles (Table
C.2) with NiMH batteries having approximately the same
capacity, and battery weights represent about 25% of the utility
vehicles?? 25-35% higher curb weights. Only the lightweight,
aerodynamically very efficient 2-seat EV1 has a practical range
substantially
Power Density. The USABC targets for power density (see Table II.1)
were set to give an EV acceptable acceleration from a battery that meets
the minimum specific energy requirements. These targets need to be met
by a battery discharged to 20% of its capacity at the lowest design
operating temperature, and until the end of battery life when power
capability is substantially degraded. (Fully charged, new batteries
typically have much higher power capability than needed by EVs.) Since
the mass-produced ICE vehicles of today generally have higher
acceleration capability than those of 5-10 years ago, the USABC
commercialization target for power density probably should also be
considered a minimum requirement. In the longer term, advances in
automobile technology??especially substantial reductions of weight and
aerodynamic drag??could result in decreased EV-battery power and
capacity requirements andor increases in EV performance, as has been
demonstrated by GM??s EV1.
1.2. DurabilityBattery Life
The useful service life of a battery is limited by loss of its ability
to meet certain minimum requirements for delivery of energy and power.

For EV batteries, the minimum requirements are nominally set at 80%
of both the new battery??s energy storage capacity and the EV??s power
capability specification. Loss of power capability (?°power fading?±)
and energy capacity is caused by cycling batteries. It can also occur
while batteries are not being cycled, as a result of chemical processes
that over time transform battery active materials irreversibly into
inactive forms, andor reduce the current carrying capability of the
battery. If these processes are relatively rapid, battery life can
become unacceptably short. Typically, power fading is the limiting
factor in EV-battery life. As will be discussed in more detail below,
the likely cost of nickel-metal hydride and other advanced EV batteries
is such that, for acceptable life cycle costs, these batteries need
to last for at least 100-120 k miles, the nominal service-life of the
vehicle. For a battery that can deliver an EV range of 100 miles per
charge, the 100k-120k mile life requirement is equivalent to the USABC
long-term target of at least 1000 deep cycles over its service life.
A 600 deep cycle, 5-year life capability??the near-term USABC
target??is almost certainly insufficient in view of the high cost of
battery replacement.

II.1.3. Safety
Today??s automobile safety requirements are very stringent, and the
assurance of a very high level of safety will be a critical requirement
for electric vehicles deployed as a broadly available new automotive
product. As a high-energy system, the battery is the main safety
challenge associated with electric vehicles. However, no statistically
valid experience base exists for defining and quantifying adequate
safety for the advanced batteries used in EV propulsion. Moreover, the
safety issues differ substantially from one type of battery to another,
and even within a battery type from one design to another. Given this
difficulty, USABC and the battery and EV developers have resorted to
characterizing candidate advanced EV batteries in terms of their
tolerance to a series of 10?°abuses?±, as a provisional indication of
the batteries?? level of safety. Representative battery abuse tests
that EV- battery developers apply routinely to cells and modules are
summarized in Appendix D. It needs to be emphasized, however, that there
are as yet no data correlating test results and failure criteria with
safety-related incidents experienced by vehicles equipped with
advanced EV batteries. Remarkably, such incidents are extremely
rare or altogether absent. Thus, while some of the abuse
tests probably represent a realistic failure mode, others may not
simulate likely occurrences, and an EV-battery failing to meet one of
the standard abuse tests could conceivably be safe under all but the
most extraordinary and unlikely conditions. Conversely, it is noted

that unsafe situations may not be fully captured by the existing abuse
tests but could surface in the future.

1.4. Convenience

Several battery characteristics that may offer particular
advantages (or, conversely, pose limitations) in EV applications can
be grouped under the broad term ?°convenience?±: for example, quick
charging capability, low self-discharge rate, and wide
battery-operating-temperature range. The USABC targets for these
characteristics form a reasonable set of requirements, but none of these
are as critical to the acceptability of batteries for EV service as
are the targets for performance, durability and safety. The numerical
values listed in Table II.1 thus appear to be desirable, rather than
required, characteristics although some of them may prove to be
important for acceptance of an EV in the market. (Not mentioned
among the requirements but also important is the stipulation
that EV batteries must be chemically and mechanically maintenance-free
to avoid the cost of skilled maintenance labor andor the
inconvenience to the owneroperator. This requirement does not
extend to electrical maintenance [such as cell balancing, etc.] that
can be provided automatically as part of the battery??s electrical-
control functions during charging or other phases of operation.)

1.5. Cost
Background. By general agreement, the costs of advanced EV batteries
having the potential to meet the other critical requirements for EV
service are a major barrier to the competitiveness and widespread
introduction of EVs. For example, the actual costs of the advanced
batteries in the EVs introduced in limited numbers over the past several
years range from nearly $$30,000 to more than $$80,000 per pack,
requiring heavy subsidies by the EV manufacturers to attract vehicle
lessees. The specific costs target for advanced batteries would be
substantially higher only if motor-fuel costs increased
drastically above $$2gal, or if the needed EV-battery
capacities were to decrease substantially below 28kWh because of
much-reduced range requirements andor greatly increased EV
efficiencies. None of these possibilities seems likely in the
foreseeable future, at least in the United States, although some of
them might materialize over the long term.

2. EV-BATTERY COST FACTORS
From the outset of this study, it was clear that battery costs were
not only important issues with the advanced systems currently used in

EVs, but were recognized as a major economic barrier to the widespread
market introduction of electric vehicles. Acquisition and analysis of
battery-cost information, therefore, became important aspects of the
Panel??s work. This section reviews the major factors that contribute
to battery cost. Additionally, an EV-battery-pack will have a thermal
management system for heating, cooling, or both, as well as electrical
and electronic controls to regulate charge and discharge, assure safety,
and prevent electrical abuse. The level of sophistication and
complexity of the needed controls depends on the requirements of
specific battery systems. The major steps in EV-battery-pack production
are shown in Figure II.2. While production activities up to the level
of modules are exclusively the province of the battery manufacturer,
pack assembly, electrical- control integration, and reliability testing
are operations frequently carried out by the EV-battery customer, the
vehicle manufacturer.
How these responsibilities are divided affects the selling price of
the battery. Thus, while the specific cost (in $$kWh) of the battery
pack ready for installation in the vehicle is the most important battery
cost characteristic, most of the cost data gathered and reported in
this study are for module costs. To arrive at the pack price, we have
added a fixed amount to the module cost, using the approximate numbers
provided by battery developers and USABC.
Direct labor costs, as a percentage of total costs, decline with
increasing capital investment in labor-saving manufacturing equipment
that becomes progressively more productive as battery production
volume rises. At any given production level, there is a tradeoff
between the costs of direct labor and the ownership costs of automated
production equipment. The inherently greater efficiency and precision
that automation enables in most manufacturing operations make large
contributions to the decline in costs as production volume increases.
The third major contributor to costs is manufacturing ?°overhead?±,
a category that includes the ownership and operating costs of plants
and equipment, as well as the costs of manufacturing support services
(manufacturing engineering, material handling, quality assurance,
etc.). The sum of materials and component costs, labor costs
and manufacturing overhead is usually termed the
(COG) for battery roduction.
how pack costs aggregate from the cost components identified above
through the various steps involved in manufacturing batteries on a
commercial scale. In the larger manufacturing facilities that could
be operational by 2003 if plant commitments were made in the near future,
costs and prices would be considerably lower than present levels.
Economies of scale will result from discounts on bulk purchases of
materials and components, higher efficiencies in the use of labor and

equipment and, especially, use of custom-designed automated
manufacturing equipment with high production rates and product
yields. Although depreciation charges related to this equipment
will contribute significantly to the factory costs of the batteries,
they will be more than offset by the savings in labor costs realized.