A bright reporter at C|Net made the discovery. Amazon says the Kindle now has a battery life of two months. Wednesday morning Amazon released a new version of the “Kindle with Special Offers” — a 3G version that’s discounted to $164. But instead of promising the usual one month of use without a battery charge, Amazon now says this Kindle’s battery will last two months!

And Amazon’s also doubled the battery life that they’re reporting for the Kindle 3 and Kindle WiFi…

So what’s going on? C|Net’s reporter has it all figured out. On Tuesday Barnes and Noble launched a brand new touch-screen Nook — and then claimed that its two-month battery life was double that of the Kindle (calling it “the longest battery life of any eReader”). “Amazon countered by magically upping the battery life of the Kindle to two months,” reports David Carnoy. But it turns out that Amazon may have had a good reason…

The Nook’s battery life was calculated by assuming just one half hour of reading time each day. “Let the math shell games begin!” joked one user in a Barnes and Noble discussion forum. “Anyone want to lay odds on who will go to 4-month battery life assuming a 15 minutes a day reading habit?”

The CEO of Kobo also took issue with the Nook’s ‘half-hour-a-day” figures, complaining “that’s not a typical usage scenario,” and arguing that the same lofty claim could be made about the battery life of the Kobo.

“It appears that [Amazon] just took issue with how its competitor was calculating and presenting its battery life numbers,” C|Net reports, noting that Amazon also updated their Kindle product descriptions with a full explanation.

“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. Keep wireless always on and it lasts for up to 10 days. Battery life will vary based on wireless usage, such as shopping the Kindle Store, Web browsing, and downloading content. In low-coverage areas or in EDGE/GPRS-only coverage, wireless usage will consume battery power more quickly.”

So the Kindle’s battery hasn’t suddenly become twice as powerful as it was before. And I thought C|Net’s reporter gave this episode the perfect epitaph. “Amazon didn’t have any comment about its number changes, but it clearly shows that the competition is intensifying in the dedicated e-reader space…”