STRONGER, smaller, lighter, and cheaper - that's what on-the-go consumers want of batteries for their laptop computers, cellular telephones, cordless screwdrivers, and (soon) electric vehicles.
Rising to the challenge are established manufacturers and start-up companies. Their research is accelerating the once-glacial evolution of two-century-old battery technology. Already, these companies have made power more portable than ever before. But the market demands even better performance, so experimentation continues.
The need is most urgent in the electric-vehicle market. Beginning in 1998, California will require major automakers to sell some vehicles that emit no pollutants. The same may happen in 13 Northeastern states. Only electric vehicles can meet this zero-emission standard, says Gordon Allardyce, director of environmental and engineering affairs at Chrysler Corporation.
But today's batteries are too heavy, weak, and costly to give consumers a vehicle matching the performance and price of gasoline-powered cars. ``The battery is the key to the whole thing,'' Mr. Allardyce says.
The Big Three automakers formed the United States Advanced Battery Consortium in 1991 to look for answers. USABC has budgeted $135 million - with half coming from the Department of Energy - to projects investigating battery technologies like nickel-metal hydride, sodium-sulfur, lithium-ion, lithium-polymer, and lithium-iron disulfide.
While they all have great potential, USABC Chairman John Wallace says, none of those technologies will be ready by 1998. That means automakers' first electric vehicles will have to use lead-acid batteries like those used in today's cars, a technology dating back to the Civil War.
Chrysler is expected to announce soon that its first electric vehicles will be powered by the Horizon, an ``advanced'' lead-acid battery made by the fledgling manufacturer Electrosource in San Marcos, Texas. Mr. Wallace says USABC has not funded research on lead-acid batteries because their potential for improved performance is limited.
But the Horizon meets or beats several of USABC's midterm performance targets. Its ratio of power to weight, which governs vehicle acceleration and economy, is three times better than ordinary lead-acid batteries. It can be recharged 50 percent more times. And it needs only half the time per recharge.
The Horizon's secret is its manufacturing process rather than new chemistry, Electrosource chairman Michael Semmens says. In an ordinary battery, lead plates dangle in an electrolyte of sulfuric acid. In the Horizon, the plates are squares of a mesh woven from a lead filament with a fiberglass core.
Far less lead is needed to generate a given amount of current, saving weight. The process of wrapping the lead around fiberglass also gives the lead high strength and corrosion resistance for a longer battery life.
The mesh plates, covered with a proprietary paste, lie in stacks in the Horizon battery. This unique horizontal configuration improves heat distribution and oxygen recombination, to allow the battery to recharge more efficiently and safely. And it keeps the plates evenly in contact with the electrolyte, which gives the Horizon longer life per charge.
Electrosource has already received a $2 million order from a company that converts vehicles to run on batteries. Solarmax, a two-year-old company based in Sarasota, Fla., is gearing up to produce several thousand electric vehicles a year, says company president Dennis Suave.
``The claims Electrosource has made are very true,'' Mr. Suave says. ``The Horizon battery is far superior to any of the other batteries we've tested.''
A typical lead-acid battery has an energy density, which measures endurance, of 25 watt-hours per kilogram. The Horizon's best competitor achieves 33 Wh/kg, Mr. Semmens says. Production models of the Horizon achieve 41 Wh/kg, and Electrosource has reached 55 Wh/kg in the laboratory.
That's still well short of the USABC midterm goal of 80-100 Wh/kg - enough to carry the whole family on a 100-mile outing with the air conditioning on. Semmens expects further improvement. ``There's a lot of potential in lead-acid that's never been mined,'' he says. Such batteries have a theoretical potential of 180 Wh/kg, close to the USABC's longterm goal of 200 Wh/kg.
``No other lead-acid battery performs like the Horizon,'' Wallace admits. But he remains skeptical that lead-acid technology will provide the performance breakthrough needed to win customers for electric vehicles. And the Horizon's price is more than double the midterm target, though it will fall as monthly production ramps up from 600 units now to 10,000 by year end.
Meanwhile, with automakers already gearing up for the 1998 mandate, ``beggars can't be choosers. We have to have something,'' Wallace says.