A Cheaper Battery for Hybrid Cars

New lead-acid batteries could achieve high performance.

Still going: Tests of a Honda Insight equipped with a novel type of lead-acid battery showed that the hybrid vehicle can run more than 100,000 miles using the new technology. Credit: Advanced Lead-Acid Battery Consortium

The future market for hybrid-electric vehicles, at least those that are affordable, isn't necessarily paved with lithium. Researchers in Australia have created what could be called a lead-acid battery on steroids, capable of performing as well as the nickel-metal hydride systems found in most hybrid cars but at a fraction of the cost.

The so-called UltraBattery combines 150-year-old lead-acid technology with supercapacitors, electronic devices that can quickly absorb and release large bursts of energy over millions of cycles without significant degradation. As a result, the new battery lasts at least four times longer than conventional lead-acid batteries, and its creators say that it can be manufactured at one-quarter the cost of existing hybrid-electric battery packs.

In the United Kingdom last week, a Honda Insight hybrid powered by the UltraBattery system surpassed 100,000 miles on a test track. "The batteries were still in perfect condition at the end of the test," says David Lamb, who heads up low-emission transport research at the Commonwealth Scientific and Industrial Research Organisation (CSIRO), Australia's national science agency. "What we've got is a lead-acid battery that is nice and cheap but can perform as well as, or better than, the nickel-metal hydride technology, which we know is very expensive."

Lead-acid batteries, invented by French physicist Gaston Plante in 1859, don't get much respect these days, despite being a crucial fixture under the hood of most vehicles. They contain lead, so environmentalists don't like them. They're heavy for the energy they store--a bad trait for mobile applications. And they degrade easily if not cycled properly. Indeed, there have been no major advances in the technology over the decades.

Meanwhile, a newer generation of batteries--most notably lithium-ion ones--are capturing the attention of investors and automakers. "Many have tried to improve the lead-acid battery, but the improvements were usually not that great or worth the added cost," says Malcolm Shemmans, founder and president of BET Services, a provider of battery-testing services to the auto industry.

To compensate for some of the shortcomings of lead-acid technology, many in the past have tried to complement the batteries with supercapacitors. In the late 1990s, for example, Lamb helped design two hybrid cars that used a 60-volt lead-acid pack and a separate 150-volt supercapacitor pack. The lead-acid system allowed the vehicles to drive in all-electric mode in the city, while the supercapacitors gave the cars the jolt that was needed for acceleration and the ability to quickly absorb energy from braking.

The cars worked well, but all the power electronics that were needed to control the two power systems were heavy and prohibitively expensive. Instead of treating the lead-acid batteries and supercapacitors as separate systems, Lamb's team decided to eliminate the need for all external electronics and instead build the supercapacitors directly into the battery. Essentially, one of the plates (the negative electrode) in the lead-acid battery was made half of lead and half of carbon, turning the battery into a supercapacitor-lead-acid hybrid.

CSIRO brought the design to Japanese battery manufacturer Furukawa Battery Company, which saw potential in the technology. After three years of collaboration, the two organizations determined that they could manufacture the UltraBattery much like conventional lead-acid batteries and at similar cost.

Meanwhile, Axion Power International, in New Castle, PA, has also developed a new type of lead-acid battery. Edward Buiel, chief technical officer with Axion, says that lead-acid batteries can play a significant role in the future of transportation and energy supply. Unfortunately, he adds, the automakers don't see the potential. "If you're not lithium-ion or nickel-metal hydride, they're not interested. It's frustrating."

Buiel says that the typical cost of a nickel-metal hydride power pack is $2,000, and close to $5,000 retail. "A comparable lead-acid could be in the range of $1,000 in low volume, and significantly less in high volume," he says. "It's a battery where the consumer could see enough fuel savings for a payback in a year or two."

Despite the reluctance of the auto industry to embrace the technology, Lamb is convinced that by 2010 there will be some Japanese-made hybrid cars on the market offering the UltraBattery option.

However, Axion might have something to say about it. "We definitely think this technology is an excellent choice for hybrid-electric vehicles," says Buiel. "There's a lot of intellectual property in this area, and most of it is owned by Axion. Obviously, if we feel somebody violates our patent, we will defend that vigorously." He says that Axion plans to launch a demonstration project in North America this year that will test dozens of hybrid vehicles retrofitted with its lead-carbon batteries.

http://www.technologyreview.com/Energy/20105/