For decades, the drive to make smaller and smaller electronics products has been powered by the continual miniaturization of circuitry and components, such as transistors.
But now that increasingly powerful hand-held and laptop products are coming on line, the bottleneck no longer is circuitry or chips. Instead, in such power-hungry products as cellular telephones and laptop computers, one of the oldest, lowest-tech components in the innards often blocks further reductions: the battery.The introduction of Compaq Computer Corp.'s first laptop computer was held up, in part, by limitations in existing batteries. In keeping with the company's Mercedes-Benz strategy, its laptop was to include internal floppy and hard-disk drives and the ability to support not just its own high-resolution, backlit black-and-white screen - but an external high-resolution, backlit color screen.
Such items are big power hogs. Existing batteries using traditional ways could not meet the task.
The Houston company's answer was twofold: first, a battery that could hold its charge for three hours and then be recharged in 90 minutes, compared with the overnight recharge periods for many laptops; secondly, hardware and software features that reduce power consumption by automatically turning off such subsystems as the keyboard, modem, hard drive or display when not in use.
Similar "intelligent power management" techniques are in use at Zenith Data Systems in Glenview, Ill. That's because rechargeable battery packs still account for about 20 percent of the weight of its 14-pound laptops - and are expected to remain such a burden.
"We don't see much in the way of advances in battery technology in the near future," Zenith computer unit's spokesman Matt Mirapaul said.
Since an Italian count stacked pairs of silver and zinc disks into something called a voltaic pile, battery makers have been endlessly searching the well-known set of available metals and elements for combinations of chemically active materials which can generate power on demand in lighter, smaller and more long-lasting combinations.
The general-purpose batteries used in flashlights and other everyday devices use carbon and zinc. In recent years, those batteries have been vastly improved with the introduction of an alkaline solution as the agent that promotes reaction.
Alkaline batteries now account for more than half of all the factory shipments of portable batteries in this country and an overwhelming majority of the disposable batteries sold here.
Such batteries are adequate even for some simple laptop computers, such as Tandy Corp.'s 100, 102 and 200 models, which primarily process text, do not have much memory storage and do not try to support fancy screens or heavy-duty storage devices such as hard-disk drives.
But users of the company's more powerful laptops, such as the 1400 LT, or portable products such as its CT-300 cellular phone, need batteries that have more power and can be used again and again.
That has promoted the use of batteries based on a combination of nickel and cadmium. Those materials have chemical reactions that can be reversed after delivering their original electrical energy.
But those batteries, found in most laptop computers, are bulky and have awkward characteristics. For instance, such batteries work best when they are completely spent and then recharged, not before. Also, users get little advance warning before the power runs out. That can be disastrous if you're in the middle of a task.
"You wouldn't drive a car with a leak in the gas tank, without a gas gauge," said Ken Rekrutiak, vice president of Moli Energy Ltd, Burnaby, British Columbia.
Moli makes a rechargeable battery based on lithium, nature's third-lightest element, the lightest metal and a highly active electrical material.
Its Molicell batteries deliver three-volt charges, instead of the 1.5 volts delivered by most AA-size batteries. That means two Molicell batteries can do the work of four comparable AA batteries.
But the batteries have other "user-friendly" characteristics, as Rekrutiak puts it. They "don't mind being partially discharged" and can be measured at any time for the remaining charge, so "gas" gauges can be put on products such as laptops.
The cells already are found in portable phones, radio-relay data terminals and the much-publicized NEC Ultralite laptop computer. That laptop, also introduced in October, weighs only 4.4 pounds - including seven AA Molicells - is 1.5 inches thick and fits in an 81/2- by 11-inch envelope. Of course, the computer does not include such features as disk drives, modems or fancy graphic displays.
But lithium is being highly touted by North American battery makers, including Eastman Kodak's battery subsidiary in Newark, N.Y., Ultra Technologies; Eveready Battery Co. Inc., St. Louis, Mo.; and Duracell Inc., Bethel, Conn.
Disposable lithium batteries were Kodak's big innovation when it entered the battery market a couple of years ago, trying to wedge its way into a consumer business dominated by Eveready and Duracell. Its nine-volt lithium batteries have a shelf life of 10 years, compared with three or four years for alkaline batteries, which Kodak also sells.
The lithium batteries have found greatest acceptance in specialized security, medical, military and consumer uses, where long life is important, says Paul Dickinson, Ultra's director of market development. The most notable use, so far, makes parent Kodak very happy. It's in cameras, particularly the new generations of highly automated, all-everything cameras, such as the Minolta Maxxum line.
Kodak has only sold nine-volt lithium batteries, since that is a natural multiple of the typical three-volt discharge of such devices. But Eveready plans to introduce 1.5-volt batteries early in 1989, using iron sulfide - "fool's gold" - as the other active material.
The lithium AA batteries will cost $2 or $3 apiece, compared with $1 each for alkaline cells, says Gilbert Merritt, director of technical resources for Eveready, but will deliver two-and-a-half times as much power and may well become the disposable battery of choice for high-tech products, such as laptops and portable phones.
That's because they work best when asked to do a lot. "This is a high-tech battery at a premium price that will give you a lot of zoom if you push it," said the technical resources director of a battery company that this past year introduced a specialized battery for portable stereo products, the Conductor.