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The Cutting Edge: Computing / Technology / Innovation : Shocking Claims About Batteries

October 05, 1994|RICHARD O'REILLY | RICHARD O'REILLY is director of computer analysis for The Times

When Dell Computer Corp. bragged a few weeks ago that the battery in one of its new Latitude notebook computers lasted 17 hours and 5 minutes in an independent lab test, I was intrigued. Short battery life, after all, is the proverbial Achilles' heel of mobile computing, and Dell was saying it had essentially solved the problem.

Then I had the opportunity to test two of the color models in the Latitude XP family, and in both cases the fancy new lithium ion batteries died in less than three hours. False advertising? Well, not exactly. But as I soon learned, battery life remains a vexing problem, and a definitive solution is nowhere in sight.

That said, I should also say that Dell appears to have gained at least a temporary lead in the hotly contested battery-life race. The company chose to make longer battery life a central feature of its re-entry into the notebook computer market--it had been forced to pull out last year after a string of failed products--and the results are impressive.

The new Dell line ranges in price from a $1,399 black-and-white model with a 33-megahertz 486SX microprocessor to a $5,000-plus fully configured active-matrix color Latitude XP with a 100-MHz 486DX4 microprocessor and a whopping 524 megabytes of hard disk storage.

All machines have built-in 3.5-inch floppy drives and full-size keys. The screens measure about 9.5 inches diagonally, which is just fine for Windows software. They also have a comfortable palm rest and a central track ball below the space bar, much like the original Macintosh PowerBook--a design I prefer.

The most original feature, though, is the lithium ion battery technology, which is also used in some Toshiba laptops. The main advantage of lithium ion batteries is that they weigh about a third less than other batteries of the same capacity and don't have the re-charging difficulties of nickel metal hydride and nickel cadmium batteries, the main alternatives. The disadvantage is cost: Dell prices the lithium ion battery at $199, compared to $99 for a nickel metal hydride (NiMH) battery. (Nickel cadmium batteries are even cheaper, but Dell does not use them.)

Now what about this 17-hour life span? For help, I turned to Marc Abrams, special projects manager at VeriTest Inc. in Santa Monica, the independent lab that had tested the Dell notebooks.

The 17 hours didn't really represent a typical user, Abrams explained. That result was just one from a series of different tests, and it was performed on a 50-MHz model with passive-matrix color screen, which uses less power than active-matrix color. The test scenario basically represented someone who turned the machine on and left it on all day, but mostly with the lid closed and not in use.

Dell achieved such astounding results because its power management system draws far less power when the computer is in "sleep" mode than any computer previously seen at VeriTest: It draws just 10 milliamps of power, compared to the previous champion miser, IBM's ThinkPad, which draws 50 milliamps. Abrams noted that some cheap off-brand notebooks don't have a sleep mode at all and merely blank the screen while continuing to draw up to one amp from the battery.

Many machines, including the ThinkPad color computer, also cheat on performance by reducing screen brightness when operating on the battery. That's a good way for anyone to extend battery life, because the screen is the biggest power drain, but I'd rather have the option of trading a bright screen for shorter endurance. The Dell Latitude XP models I tested showed the same brightness whether I was on battery power or had the AC line plugged in.

I did my own tests with a software program from DiagSoft Inc., part of is PowerMeter performance-testing software, which worked the computer harder than users normally would. I ran the test with all power management disabled, which prevented the computer from shutting down the hard drive, central processing unit or screen. And the program itself recorded the time on the hard disk every five seconds, which is more disk exercise than would normally occur.

The VeriTest measures, by contrast, use a mechanical gadget, Keyboard Annie, which is programmed to type a series of real keystrokes into real Windows programs, with periodic bursts of activity and pauses, just the way most people actually work.

So how long will the Dell notebooks with lithium ion batteries actually run? They lasted longer than any other make VeriTest has examined. According to Abrams, "You really can fly across the country with it."

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