By Philip Elmer-DeWitt

    There’s a surprising level of awe and wonder in the tech press about the batteries in the MacBook Pro computers that Apple (AAPL) unveiled last week — especially since they’ve been around for more than a year.

    “Battery life to die for,” was the headline of a widely quoted review in AnandTech.

    “Battery technology simply doesn’t advance this fast,” wrote Computerworld’s Seth Weintraub.

    “This kind of battery life is reserved for iPods and mobile phones, not laptops,” gushed Leander Kahney in Wired’s Cult of Mac. “Who cares if the battery is sealed in?”

    That last remark is especially surprising given that one of the knocks against the first Apple computer to deploy the new battery technology — the MacBook Air that Steve Jobs introduced in January 2008 — was that its battery couldn’t be replaced with a fresh one if it ran out of juice in mid-flight over the Atlantic.

    But the first MacBook Air only promised 5 hours of computer power. Apple claims the new MacBooks will deliver 7 or 8 hours on a single charge and last up to 5 years — longer than the expected life of the average laptop.

    AnandTech tested the first claim in a series of benchmarks reproduced below the fold. Bottom line: the new MacBook Pro delivered …

    • 8.13 hours of light wireless Web browsing, and

    • 4.92 hours of heavy downloading.

    According to Anand Lal Shimpi, who ran the tests, he saw 50% to 100% improvement in battery life over the old MacBook Pros — considerably better than the 46% theoretical improvement he expected based on the new battery’s capacity.

    His review offers several explanations for the improvement:

    • new battery technology (lithium polymer vs. lithium ion)

    • new form factor (rectangles vs. cylinders)

    • better battery management (adaptive charging that senses the power needs of each cell).

    Whether Apple can deliver on its promise of five years of battery life (based on 1,000 recharges vs. 300) remains to be seen. If the battery does need replacing before the computer dies of natural causes, Apple technicians will do the job (and dispose of the old one) for $120 a pop.

    You’ll might be able to get an independent technician to do it for less, but probably not without voiding your warranty.