The Kindle runs longer than Amazon claims—according to Barnes & Noble?

Used for an hour a day, the Kindle e-book reader runs for a month without needing a battery charge, says Amazon. But Barnes & Noble, its key competitor, begs to differ: The Kindle has almost double that battery life, according to test results B&N released this week.

The claim, contained in an e-mail B&N sent to reporters, marks a curious twist in a battery-life battle that's been brewing since last week. The tussle apparently matters a lot to B&N and Amazon. More later on why it may be moot to consumers.

The fight began after Barnes & Noble announced its new Nook Simple Touch Reader and proclaimed that it offers "best-in-class battery life." Amazon responded to B&N's claims of a 2-month battery life for the Simple Touch by revising, upward, its battery-life specs for the Kindle.

Amazon now says of the Kindle that "A single charge lasts up to two months with wireless off based upon a half-hour of daily reading time. If you read for one hour a day, you will get battery life of up to one month."

But B&N's "side-by-side tests" of the Simple Touch and Kindle, "under the exact same conditions," suggest Amazon is being too modest. B&N reports the Kindle lasts for "56 hours," assuming the Wi-Fi is turned off and pages are turned at the realistic pace of 1 per minute. At an hour a day of reading, that's 56 days, nearly twice the 1-month claim made by Amazon.

Of course, B&N released its data not to give a boost to its competitor but to assert even longer run times for the Simple Touch compared with the Kindle. B&N claims the Simple Touch ran more than twice as long in its tests as the Kindle—150 hours, to be precise. At the same hour-per-day reading time as Amazon uses for its Kindle claim, that's a mind-boggling 5 months between charges, or nearly twice as long as B&N's own 2-month claim.

Are these figures reliable? A better question might be: Do they really matter?

In our experience, devices (such as the Kindle and Simple Touch) that have low-energy E Ink screens run for more than ample time on a charge. We're not sure that how many months they claim to run matters much. A supposed run-time of 4 to 5 months rather than a month or two might, we suppose, be marginally more convenient. But it could also allow more opportunity to, say, misplace that seldom-used battery charger.

Our bottom line with battery life and e-book readers: Pay attention to whether the battery times (based on manufacturers' claims) that we include in our Ratings are in hours (like the models that have backlit LCD screens, such as the Nook Color) or in days or weeks (like the models with E Ink screens). After that, worrying about relative differences in battery life may consume more energy than it's worth.

That, in large part, is why we don't test battery life for e-book readers, although we do for most other mobile devices whose run times are typically shorter—and where differences are more important, we think.

We continue to test the new B&N Simple Touch Reader in our labs and will have more information soon. It will soon be added to our Ratings, which are available to subscribers.

—Paul Reynolds