Auto Industry Working Hard to
Make an Electric Vehicle Battery |
Charles J. Murray, Senior
Technical Editor -- 4/14/2008 9:49:00 AM |
To an engineer, it looks obvious.
Gasoline packs 80 times more energy per kilogram than a lithium-ion
electric vehicle battery. It holds 250 times more energy than a common
lead-acid battery. So, it’s a no-brainer. Batteries can’t possibly
deliver the energy needed to power the future of the auto industry,
right?
Wrong. With vehicle exhaust being blamed for global warming and with
concerns over foreign oil availability growing, the auto industry has
re-ratcheted up its efforts to develop an electric car and the battery
still sits smack-dab in the middle of Alternative Energy Highway.
“The battery is central,” says Mark Verbrugge, director of the
Materials and Processes Lab. at GM
Research Labs. “We know and understand all of the technologies that
are needed, other than the battery.”
Indeed, battery technology is still, to some degree, a mystery. But
automakers don’t want to wait. General Motors has promised a 2010
delivery date for the Chevy
Volt,
a “plug-in hybrid” vehicle that uses lithium-ion batteries. Meanwhile,
Toyota and Ford are working on plug-ins while Chrysler has placed a
handful of Dodge Sprinter plug-ins in a test fleet. All will draw power
from batteries.
Questions remain, however: Can today’s battery technology sustain an
EV market? Do the batteries pack enough energy? Is their cost low
enough? Is the durability there? Are they safe?
The answers are complex and varied. Most automotive engineers and
electrochemists agree on one point, however: A big, full-featured,
battery-powered car isn’t feasible yet. Energy densities are still too
low; range is too short; recharge time, too long. Because no one as yet
can build an electric vehicle with a 300-mile range and 15-min recharge
time, batteries aren’t about to replace the internal combustion engine.
“We’d like to have a direct replacement for what we have today,”
says David Swan, president and engineer for DHS Engineering Inc.,
a consultant to the EV industry. “But creating an electric vehicle that
matches our current vehicles — performance for performance, price for
price — is extraordinarily difficult.”
Still, there’s a market there, albeit a niche market. Such companies
as Global
Electric Motorcars
(GEM), Zap!
Electric Cars and Zenn Motor Co. are producing tiny,
battery-powered neighborhood vehicles. Daimler is testing a diminutive
EV in London.
Moreover, plug-in hybrids are on the rise. Plug-ins, which use
internal combustion engines to extend range, make it easier to build an
EV battery because they eliminate concerns over specific energy.
Even so, makers of plug-in batteries say the task is not a slam
dunk. “This is a big, big challenge,” says Mohammed Alamgir, director
of research for Compact Power,
Inc.,
a battery maker for the GM Volt project. “People in this industry are
accustomed to teeny-weeny cell phone batteries. Now we’re looking at a
battery that has to be forklifted. It’s a huge jump in scale.”
The Energy Density Battle
The drive to make an electric vehicle battery is hardly new. Legend
has it that Thomas Edison and Henry Ford collaborated on the challenge
a century ago. Given five years, they said, they could lick the battery
problem. But while they developed a product, their battery’s energy
density was just a fraction of that of a gallon of gas, and the EV
gradually disappeared.
During the 1980s, the auto industry again made a collective effort
to beat the battery problem. Again, it failed, as EVs from Chrysler,
Ford, GM,
Honda, Nissan and
Toyota were
shelved in the late
1990s.
The issues facing EV batteries of a decade ago were the same as
those of today: Energy density, recharge time, cost, durability and
safety were the big challenges.
Energy density was prime among those, mainly because it directly
translates to vehicle range: the higher the energy density, the greater
the range between recharges. In a full-size sedan, for example, a
specific energy of 100 W-hr/kg translates to approximately 100 miles of
range. To boost range, automakers need to pack more batteries on board,
which can dramatically increase mass.
Mass-related issues were the reason that battery power long failed
to capture the fancy of automotive engineers. Many looked at the
numbers and scratched their heads. Today’s best batteries, for example,
offer a specific energy of approximately 150 W-hr/kg. In contrast, the
accepted specific energy of gasoline is about 12,722 W-hr/kg. Engineers
often argue about how much of gasoline’s energy is usable, but even if
only 4,000 W-hr/kg is usable, gasoline still packs 25 times more energy
than a lithium-ion battery. That, in turn, means that the mass of a
good EV battery is 25 times that of gasoline.
Worse, batteries recharge slowly. Using a 110V outlet, an EV battery
typically hits full recharge in more than six hours.
“You have this great inequity of the density of the energy
(source),” says Larry Oswald, chief executive officer of Global
Electric Motorcars, a Chrysler company. “A battery is like a heavy fuel
tank with a very small neck in it.” During the 1990s, battery makers
skirted the energy density deficiencies by stretching the truth. They
talked about ranges of 400 miles and recharge times of 15 min. Neither,
however, came to pass.
“We hurt ourselves badly by exaggerating where we were, where we
were going, and how long it would take to get there,” says Swan, who
owns three electric vehicles. “The battery makers would internally
calculate the range based on a car that used very little energy. They
made all kinds of great assumptions and, lo and behold, on paper they
were getting 400-mile ranges and 15-minute recharge times.”
Dealing With Cost Issues
That’s why the plug-in hybrid has emerged as such an important
alternative. With the plug-in, range becomes a non-issue. The United
States Advanced Battery Consortium
(USABC), an organization formed by American automakers, has set goals
for plug-ins with 10- and 40-mile ranges. With the shorter range
requirements, it’s not necessary for battery makers to achieve specific
energy levels approaching 300-400 W-hr/kg. Rather, the USABC has set a
goal for the 10-mile plug-in to reach 56 W-hr/kg and for the 40-mile
vehicle to achieve 96 W-hr/kg.
By backing up the battery with an internal combustion engine and a
generator — as the plug-in hybrid does — auto executives say they could
dramatically improve the driving range of EVs. GM execs, for example,
say the Chevy Volt could have a range of 400 miles. “If you lived 30
miles from work and charged your vehicle every night when you came home
or during the day at work, you could get 150 miles per gallon,” GM Vice
Chairman Robert Lutz told Auto Show attendees in 2007.
Still, there’s an unresolved cost issue. To keep costs reasonable,
the USABC has set goals of $293/kW-hr for a 40-mile plug-in and
$500/kW-hr for a 10-mile vehicle. Here, too, shorter range has its
advantages. Because short-range battery packs can be smaller, battery
makers no longer need to shoot for the exceptionally difficult figure
of $100/kW-hr, which was the long term goal of a decade ago.
Nevertheless, all acknowledge it won’t be easy. Experts asked by Design
News
to estimate the going rate for today’s lithium-ion battery said it
ranges between $500 and $1,000/kW-hr. Lithium-ion cells alone, they
say, typically cost $300/kW-hr. But EV batteries costs must necessarily
include packaging, protective circuitry, cooling systems and dealer
mark-ups, along with the cell itself.
“It’s not a simple matter,” says Elton Cairns, a professor emeritus
of chemical engineering at the University
of California-Berkeley,
as well as a former developer of fuel cells for General Motors cars and
a designer of batteries for the Gemini spacecraft. “When you put
electronic circuitry and packaging in, you’re probably right around a
$1,000/kW-hr.”
Most experts agree, however, the brunt of the remaining work is
engineering, not invention. “The issue now is one of scaling,” says
David Cole, director of the Center
for Automotive Research.
“From our perspective, it appears some of the critical inventions have
been made. What remains is some good engineering development.”
Safety Solutions
Completing that engineering before the publicly announced start
dates, however, is another matter. General Motors, in particular, has
stuck to its original proclamations of a 2010 introduction date for the
Chevy Volt. Given vehicle development times, however, battery makers
must have their products ready now, or very soon, to meet that schedule.
The good news is that makers of lithium-ion batteries say they’ve
licked the safety issue that has grabbed headlines in the past. Thermal
runaway, which has reportedly plagued lithium-ion in laptops and cell
phones, has been eliminated through a change in chemistries. Instead of
using cobalt oxide in the positive electrode, EV battery makers are
employing alternatives. A123
Systems,
for example, employs a nano-phosphate material in its cathode while LG
Chem and Compact Power Inc. use a manganese-spinel chemistry. Such
chemistries are said to prevent overheating of the battery during
recharge, which can reduce life and possibly even cause fires.
Battery makers are also dealing with heat issues by adding cooling
systems to next-generation battery packs. Such battery packs typically
use liquid coolant that flows in channels between the cells, thus
drawing off heat. They’re also employing battery management electronics
that help keep voltages in line as the batteries cycle.
“Safety is a huge concern,” says Donald Hillebrand, director of the Center
for Transportation
Research at Argonne National Lab. “But there are chemistries out
there that will solve the problems.”
Still, the 2010 schedule presents a monumental challenge to solving
those problems. Automotive engineers worry that there won’t be
sufficient time to study and test battery packs in everyday conditions.
“The big risks we have to overcome if we expect to see widespread
implementation are quality, reliability, and durability,” says
Verbrugge of General Motors. “We’d like to get at least three to four
years (of testing) on these batteries.”
Battery makers, some of whom have already delivered battery packs to
tier-one suppliers, say they performed accelerated life tests on the
batteries with exposure to various ranges of temperature. Executives at
A123, however, say their designs are not “locked down,” meaning that
changes could still be made.
For automakers, the durability issue is inextricably linked to cost.
“The auto industry is very concerned about the cost numbers because,
ultimately, they not only have to buy the battery, they have to
warranty it,” says Hillebrand of Argonne. “If the warranty is 120,000
miles or 10 years, they don’t want to have to start swapping out
batteries at that point. That’s one of the reasons they’re so nervous
about the cost numbers.”
Hard Work Ahead
With such struggles still looming on the horizon, few experts are
looking past the plug-in hybrid. Most say automakers have their hands
full now. They’re not going to start talking about big, full-featured
battery-powered cars just yet.
“When you listen to the big automakers talk about their plans for
plug-ins, EVs and hybrids, they all say the same thing,” Hillebrand
says. “They say they are committed to production, they really intend to
do it, but then they pause and add, ‘... if the battery technology is
available.’ Anybody who is seriously involved in this is still staring
at that battery issue.”
Moreover, experts say battery makers and the auto industry need to
work together to keep battery production in the U.S. “Right now, we are
concerned about using imported petroleum,” Hillebrand says. “We haven’t
accomplished anything if we trade our dependence on imported oil for a
dependence on foreign-made batteries.”
Experts also agree on another point: Commonly repeated stories of a
magic battery, suppressed by big oil companies and hidden in a basement
in Detroit, are folklore. Battery improvements will be eked out in tiny
increments over time, largely through the sweat and hard work of
electrochemists and automotive engineers. There is no other way.
“It would be wonderful if that magic battery in the basement
existed,” Swan says. “But it doesn’t. We just have to keep methodically
making improvements.”
|