FARHAD MANJOO: It’s the battery, stupid: The looming 4G smartphone crisis.

Whatever other features it may have, a phone’s battery is its limiting factor. If the battery doesn’t work, nothing else does. This week J.D. Power and Associates put out its 2012 smartphone customer satisfaction survey, and the results bear this out. The study shows that battery life is one of the most important factors in determining whether people love or hate their phones. Owners of 4G phones were less happy with their devices’ batteries than owners of 3G phones, mainly because 4G phones don’t live as long as 3G ones. What’s more, among people with 4G phones, battery life was the deciding factor in whether or not you’d be willing to buy the same brand of phone again. If you give your phone a 10 out of 10 for battery life, you’re definitely buying that same phone next time. If you give it anything less, you’re going to look elsewhere for your next device.

That underlines a looming problem in the smartphone business, one that will haunt every manufacturer and may undermine the post-PC revolution over the next few years: Every year, everything about phones keeps getting better—except the battery.

Batteries don’t follow Moore’s Law.

UPDATE: Reader Matt Andrade writes: “If Batteries followed Moore’s Law, by now my MacBook Pro, fully charged, would be able to power my house.”