Why Your Laptop's Batteries Die So Fast

Imagine if automakers got together and started measuring the gas mileage of new cars with a cool test of their own making—one in which the cars were rolling downhill with their engines idling. Suddenly you'd have some pretty amazing claims: Why, that three-ton SUV gets 300 miles per gallon! This subcompact gets 500! In tiny print at the bottom of the window sticker you'd find a disclaimer saying that, well, um, you know, your mileage may vary.

Crazy, right? Yet that's more or less what's happening with laptop computers and their battery lives. Right now, I'm looking at a Best Buy flier touting a $599 Dell laptop that gets "up to 5 hours and 40 minutes of battery life." Down in the fine print comes a disclaimer explaining that "battery life will vary" based on a bunch of factors. Translation: you ain't gonna get five hours and 40 minutes, bub. Not ever. Not even close.

So how can Dell and Best Buy make that claim? These battery-life numbers are based on a benchmark test called MobileMark 2007 (MM07). The test was created by a consortium called BAPCo (Business Application Performance Corp.), whose members are—you guessed it—computer makers and other tech companies. AMD, the No. 2 maker of microprocessors, is a member of BAPCo, but now has become a whistle-blower. AMD says PC makers know full well that the new tests produce misleading numbers, but they are touting them anyway.

Laptops score big numbers because they're tested with screens dimmed to 20 to 30 percent of full brightness, the Wi-Fi turned off and the main processor chip running at 7.5 percent of capacity—just like those cars idling downhill. Techies and industry insiders have long known that official battery-life claims are pretty much worthless. But regular folks don't. As a result, some are getting pushed toward pricier machines by sales reps who tell them they'll get an extra hour of battery life. Those customers may be paying a premium and getting nothing. "There's only three endings to this story," says Patrick Moorhead, a marketing vice president at AMD. "Either the industry regulates itself, or the FTC steps in and regulates us, or we get hit with a class-action lawsuit. I suggest the industry go with the first option."

AMD is recommending computer makers adopt a new way of measuring battery life, using two states: "active time" and "resting time," similar to the way cell-phone makers describe the "talk time" and "standby time" of a phone. A Dell executive says that approach makes sense, and that the company is considering providing customers with information beyond the MM07 scores. "Customers expect the advertised battery life to reflect the way they really use the product," says Ketan Pandya, head of AMD-based products at Dell.

AMD isn't leading this crusade out of a sense of altruism. Its real gripe is that MM07 gives Intel, its archrival, an unfair advantage. AMD claims MM07 was created in Intel's labs and rigged so that Intel chips would outscore AMD chips, since AMD chips draw more power when idle. (AMD says that in real-life usage, laptops using its chips perform comparably to Intel's.) AMD also points out that the president of BAPCo happens to be the head of performance benchmarking at Intel.

Intel says this is all hogwash. An Intel spokeswoman says that just because the consortium's president is an Intel exec doesn't mean Intel has special influence. Meanwhile, she can't resist taking a crack at AMD: "You will often find that companies who are behind in performance sometimes challenge independent and standards-based benchmarks," she says via e-mail.

Intel and AMD are the Bickersons of the computer industry, with AMD always complaining that Intel is cheating, and Intel always responding that AMD should quit being such a crybaby. But lately AMD has been landing some punches. In May, European antitrust regulators smacked Intel with a $1.45 billion fine, claiming Intel used unfair tactics to bully AMD. (Intel plans to appeal.)

Meanwhile, out in the marketplace, the crazy battery claims persist. Dell says its $2,000 Adamo notebook will run for more than five hours, but The Wall Street Journal got only two hours and 44 minutes. Apple claims eight hours of battery life for its $2,800 17-inch MacBook Pro, but CNET got only four hours and 14 minutes. This stuff is so pervasive that professional reviewers see company-generated battery-life claims as a joke. "The rule of thumb is that in real-world use you get about 50 percent of rated battery life," says Mark Wilson, associate editor at Gizmodo. "It's not that companies are lying, but they're stacking the deck in their favor. [Their claims] are misleading to the general public." That's something to keep in mind next time you're out shopping for a laptop.