We hate to rain on iSlate’s apotheosis, but some of us are wondering about battery life.

A portable computer is only as good as its battery. A blogger with the handle of “Andrew”, writing for TabletPCReview.com, said that “Whenever we review notebooks one of the questions that always needs to be answered is, what’s the battery life like on this tablet? We all know manufacturers overstate the quoted battery life for a system, probably because they test for battery life under ideal conditions for getting a high number. For example, wireless off, processor underclocked, system idle, LCD brightness set to low, no DVD and so on. So when your notebook with a quoted 5 hour battery life actually gets three hours, you’re left wondering what happened to those other two hours the manufacturer got?”

Andrew wrote that in 2007, but the fundamental issues have not changed since then.

A January 26-scheduled announcement by Apple, which few pundits believe could be about anything else than the imminent release of a tablet-sized computer/e-book reader, has created nearly messianic frenzy. A New York Times columnist said that some are calling the device a “Jesus tablet”. But at least one authority, physicist Eric Hellmann, thinks we should look under the hood before declaring January 26th a religious holiday.

Hellman, whose popular blog Go To Hellman covers the e-book scene, has speculated on the device’s power source. “The design problem is the battery,” he recently wrote. “Assuming that the iSlate is a multimedia device implies that it’s not an e-ink device. It’s going to have a screen not so different from an iPhone screen, and that will consume power. That will in turn require a battery proportional to the iPhone battery, and batteries are what cause iPhones to be reasonably heavy for their size. The Kindle works as a book-replacement because it’s light enough; I’m guessing the iSlate will be a more of a tv than a book.”

Apple will undoubtedly imbed a state of the art battery in its tablet, but when you consider the load that a tabet will have to pull – movie and game videos, photo archives, videocam, multitouch screen, full color e-books, magazines, newspapers, music, plus countless juice-draining apps, to say nothing of the demands of the tablet’s own operating and processing system, you have to wonder whether Apple’s battery, or anybody else’s at this moment in history, will be able to do the job without adding an unacceptable weight burden.

Knowledgeable insiders confirm these concerns. When a website named islate.org posted some allegedly leaked specs (you can read them here), one commenter wrote that “for as thin as the device is intended to be, there is no possible way it’ll run a HD, 2Gb RAM, and a Core 2 Duo processor. Factor in the large multitouch screen and you could expect a battery life of about 15-minutes with those specs, AND it’d be too hot to handle AND weigh a few pounds. No way.”

There will undoubtedly be a stampede to snap up the iSlate, but the coolheaded will scrutinize the specs before committing to the hefty – rumored at $1000 – price of a device that, if you believe some iSlate evangelists, embeds nothing less than the spiritual hopes and dreams of humankind within its fragile case.

Richard Curtis