Lenovo tested the laptops using the MobileMark 2007 benchmark. The company is also offering another set of batteries with a slightly lower runtime, but which will guarantee the promised runtimes for three years. The batteries are available on all T-series and X-series ThinkPads.

Strong endurance and high capacity (the number of times a laptop battery can be recharged and maintain its runtime) represent the holy grail of PC vendors, who normally have to heavily trade one for the other.

For example, lithium-ion batteries are notorious for wearing out quickly, with battery life commonly shrinking by one-third or a half after a year or two. Every lenovo battery recharge generates heat, which degrades the charge-holding material — the Lithium cathodes — inside the battery. Packing more cathode cells into a battery to increase runtime tends to result in more heat, which cuts the battery’s life span further, according to Robin Tichy, a technical marketing manager at battery manufacturer Micro Power Electronic Inc.

Similarly, increasing voltage to more quickly recharge batteries — a feature sought by on-the-go businesspeople — tends to shorten life span, because of the heat and the extra metal needed to collect that current.

“There is no super magic formula where you can suddenly get fast charges without sacrificing something else like capacity,” Tichy said.

Improvements in battery technology have lagged over the past 20 years, she said, noting that the capacity of state-of-the-art lithium-ion batteries has increased by only about 3% a year during that period. “We’re just looking at incremental improvements,” she said.

Majapuro credits the endurance and capacity boost in Lenovo’s new laptops to a pair of steps taken by the company’s developers.

First, the development team improved the power managers in the T- and X-series ThinkPads to enable devices to adapt their recharging styles to their users. For instance, if users generally keep their laptops plugged in for a long time, the batteries will be charged more gently, which extends battery lifetime.

Second, to ensure its three-year batteries last as guaranteed, Lenovo doesn’t let its ThinkPads tap 100% of the battery in the beginning. “We don’t give all of the capacity at once to a customer,” Majapuro said. That leaves cells fresher for a longer period of time.

For users more interested in long-term battery life, HP offers special Sonata batteries as options on certain laptops.

Designed by a start-up, Boston Power Inc., the lithium-ion Sonata batteries are guaranteed to be rechargeable for at least three years, or about 1,000 charge cycles.

Moreover, the lithium-ion Sonata batteries (lenovo notebook batteries)can be recharged quickly without shortening their life span, says Boston Power CEO Christina Lampe-Onnerud. The batteries can be charged to 40% of capacity in 10 minutes, and to 80% in 30 minutes, she noted.

The trade-off, however, is an unimpressive runtime of about four hours.

In an interview late last fall, Lampe said Boston Power already knows how to make 24-hour batteries.

“Our primary agenda is to drive up capacity (number of charge cycles). But our road map includes both higher capacity and longer runtime,” she said.

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