Thursday, January 24, 2008

A Cheaper Battery for Hybrid Cars

New lead-acid batteries could achieve high performance.

By Tyler Hamilton

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.