With so much media attention showered on nickel-metal hydride and lithium-ion batteries that power the electric motors in hybrid vehicles, it's easy to forget that lead-acid batteries are omnipresent in the hybrid fleet.
Lead-acid battery makers say their product will continue to play an important role in the auto industry, but that's not stopping them from researching and developing new chemistries to meet the power needs of future vehicles.
"In the lithium- and nickel-powered cars there is a small lead-acid battery that's used for starting those cars. The (Toyota) Prius has a lead-acid battery in it—they all do," said Tom Granville, chief executive officer of Axion Power International Inc., a New Castle, Pa.-based battery maker.
"Even the (Chevy) Volt has a lead-acid battery in it," Daniel R. Langdon, president of privately held battery maker East Penn Manufacturing Co. Inc., said. The Lyon Station, Pa.-based company manufactures the Deka battery brand.
Indeed, while new battery formulations like lithium-ion and nickel-metal hydride have stolen the limelight from the humble lead-acid battery, its role in new vehicles has remained fairly constant. A mild hybrid, like Toyota Motor Corp.'s popular Prius sedan, combines a smaller combustion engine with an electric one that is powered by a nickel-metal hydride battery.
But as Granville pointed out, the Prius still relies on a 12-volt lead-acid battery to spark that combustion engine to life. The same battery powers the Prius' electrical systems, like air conditioning, power windows, radio and windshield wipers. Since car interiors have certain standard design features, like wiring and voltage requirements, it makes sense to include a smaller lead-acid battery to run those systems.
So while the high-technology batteries grab all the attention, the Prius' lead-acid battery serves the same functions it would in a standard combustion engine vehicle, albeit as a slightly smaller version.
The main reason for retaining the lead-acid battery in the system is its reliability.
"I don't see today that there will be a technology to take the place of a lead-acid battery for starting purposes. If you have a combustion engine, you will still have a lead-acid battery as part of the setup," according to Alex Molinaroli, president of Johnson Controls Inc.'s Power Solutions Group.
"It's in every hybrid car," Granville said. "It's required in order to meet cold-temperature performance and to meet the airport test—restarting a car that's been sitting there for 30 to 35 days."
Meanwhile, newer formulations like lithium have earned an unenviable reputation for being unstable and, at times, dangerous. Who could forget the exploding Sony Corp. laptop batteries recalled in 2006, or General Motors Co.'s troubled 2007 Saturn Vue Green Line, whose battery pack experienced sudden voltage drops? The automaker instituted a voluntary recall and replaced 9,000 battery packs in 2008 to address the problem.
In contrast, lead-acid is a proven, century-old technology that continues to foster innovation. One form of advanced lead-acid battery has even found a role in micro-hybrid applications. Micro refers to the degree of hybrid technology in the car rather than the vehicle size, and most micro-hybrids are simply conventional cars fitted with stop-start technology that turns off the engine each time the vehicle comes to a complete stop.
While the technology seems simple, the demands it places on the lead-acid battery aren't. The battery must power the cabin's electrical systems and seamlessly restart the engine each time a driver takes their foot off the brake.
"The technology cuts carbon dioxide emissions by around 15 percent, and it saves fuel in a like amount so it increases your miles per gallon by about 15 percent. If you add mild regenerative braking into this equation, you can get it up by about 25 percent, and the cost of doing this is just a few hundred dollars as opposed to a nickel-metal hydride or a lithium battery, which would cost a few thousand," Granville said.
European original equipment manufacturers (OEMs) began introducing stop-start technologies in their fleets to meet the tighter emission standards due to come into force in 2013, but they ran into trouble while working with traditional lead-acid batteries. After 4,000 to 6,000 cycles—roughly four to six months in a hybrid stop-start operation—the charge would drop to about 20 amps from 80 amps and refuse to recharge.
Axion developed a solution to the problem, which resulted from a buildup of sulfide on the negative electrode. By replacing the negative lead electrode with a carbon one, Axion's batteries avoid the sulfide buildup that renders traditional batteries inefficient. "The product cycles longer and more efficiently, and that's a very important part of the hybrid market," Granville said. "Everyone thought that lead-acid would be frozen out of these markets, and now there's apparent potential to use advanced lead-acid to do the micro-hybrid applications."
Indeed, in the months following the European Commission's introduction of tighter emission standards, Axion was swamped with inquiries from Europe's largest OEMs. "We're a small company in New Castle, Pa., and all of a sudden we had some of the largest car manufacturers in the world requesting meetings with us and wanting to get our product into their test vehicles," Granville said.
Axion got another boost last August when its partnership with Exide Technologies, one of the largest international battery producers, received a $34.3-million grant from the U.S. Energy Department to develop lead-carbon technology for micro-hybrid applications under the American Recovery and Reinvestment Act.
"It's what I call the circle of green—building the economy, producing jobs in this green economy, reducing foreign oil dependence so that the dollar stays here in this country, better air quality, recycling. It's the whole shooting match, really," Granville said.
While Axion focuses on lead-carbon, East Penn Manufacturing is hedging its bets by pursuing research on a variety of battery chemistries as the company develops products for vehicles of the future.
"I think you need to be hedging, looking where it's going," Langdon said. "We have to be flexible enough in our new product development so that we can meet the demands of the consumer in the future, whether that's lead-acid, carbon lead, lithium or something else.
"We have to be in all those technologies in the next 10 years to make sure we have a viable product line," he added. "There very well may be a place for both. We're not looking at it as just being in the lead-acid business. We know how to manufacture, we know how to handle materials. All of us in this business are looking at where the future technology is going to go and we're getting in line for where those opportunities can take us, whether its lead-acid or not."
East Penn Manufacturing is pursuing some lead-carbon projects, but declined to comment on the technology due to non-disclosure agreements. The company also is working on the development of advanced lead-acid batteries, and last August received a $32.5-million grant from the Energy Department to expand production capabilities of these batteries in the United States.
Langdon readily acknowledges that the company is seeking opportunities outside the lead-acid battery arena. "If we saw we had an opportunity in lithium, certainly we'd pursue it. We're certainly not turning a blind eye. That could be one of the products we make in the future," he said.
Molinaroli holds a similar view, noting that Johnson Controls' Power Solutions Group—with sales of nearly $4 billion in fiscal 2009—was the company's most profitable business. It has been working on both flooded lead-acid batteries and advanced absorbent glass mat (AGM) batteries in Europe. This includes an enhanced flooded lead-acid battery with carbon additives, while its partnership with French battery maker Saft SA manufactures lithium batteries used by Daimler AG in its Mercedes-Benz hybrid.
"We have lots of activity with other chemistries, including lithium, but we believe it will be more than one chemistry solution. The lead-acid chemistry will be around and several other chemistries will come forward," he said.
"I don't know if there's going to be a winner. We need to know the demands for the applications from OEMs so we can anticipate how far those chemistries can go, and we haven't yet been able to get an answer from our customers so we're pursuing both."