The new, high-octane iPhone 3GS is loaded with features that could light up your life -- but its battery isn't one of them.

Buyers are finding that the device, introduced two weeks ago, has trouble making it through a workday without a rest stop at the electrical outlet. It's proving to be something of an Achilles' heel on Apple Inc.'s flagship device, more than 1 million of which were sold in the first weekend.

Even the company suggests on its website that users disable some of the phone's most vaunted features, including the faster 3G network itself, to keep it from shutting down during the day.

Industry officials and outside experts sketched a complex picture of the technical and bureaucratic limits that might explain why, after two years and three generations of the device, the newest iPhone has less stamina than the first.