Ten years ago, everyone expected massive improvements in battery technology for laptops, mobile phones and other mobile gadgets.

I mean, why not? Everything else inside our favorite devices is increasing and improving by leaps and bounds -- and getting much cheaper at the same time.

Moore and his Law have been bringing us exponential improvements in processing power. Huge numbers of small improvements have been growing the size or capacity of LCD screens and flash storage while dropping the prices.

Mobile phones have undergone a convergence revolution: GPS, higher-quality cameras, bigger screens, accelerometers, "force-feedback" haptics and more.

Laptops have become thinner, lighter, way more powerful and with cool new input options and tablet configurations.

Everything has changed in the past 10 years. Everything except for batteries.

With only minor improvements, we're still using the same old lithium-ion battery technology that was invented in the '70s. The "History" section of Wikipedia's "Lithium-ion battery" page ends in 1996 -- the last time anything happened to the technology exciting enough to make it into Wikipedia.

So if batteries aren't much better, what made it possible for Dell to announce a laptop last week that gets 19 hours of battery life?

How Dell gets 19 hours of battery life

Dell's Latitude E6400 doesn't really have a 19-hour battery. It has a 10-hour battery, plus a snap-on, 9-hour battery. Both of these are "upgrades" that will set you back about $500 above the base price. Still, 19 hours for a desktop-replacement-class laptop is mind-blowing at any price.

Dell invented new technology that includes both hardware and software, and it relied on both internal R&D and partner cooperation to trick the batteries into giving up less power. On the Latitude E6400's maximum-battery setting -- which Dell calls "All-Day Battery mode" -- the laptop screen refresh rate and brightness are reduced, the optical drive is shut down and other power-saving configuration changes are made.

Separately, Dell developed a new system called Latitude ON, which extends laptop battery life to days, rather than hours. It does this by using a second operating system (Linux) and a second storage medium, which is a low-power flash drive. You can do anything you want using the ON system, as long as the only things you want to do are use e-mail, surf the Web and engage in a few other basic tasks. You can't install anything on the ON part of the system. Still, it's yet another example of how companies are leveraging dramatic improvements in laptop technology to extend battery life -- without the batteries themselves getting much better.

Hewlett-Packard plans to compete with Dell's Latitude E6400 system with its forthcoming Elitebook 6930 system, a full-size notebook that HP claims will get a whopping 24 hours of battery life per charge. Like Dell, HP isn't using ultra super megabatteries, but two good-but-standard batteries augmented by a wide range of tricks, including flash storage and very advanced, software-based power management. The company hasn't revealed many details, but it has reportedly confirmed the 24-hour battery life achievement.

Of course, all this battery-life-extension technology is built on top of Intel's already impressive mobile processor technology. Intel has been leading the industry charge for more energy-efficient mobile technology for many years. The Dell system uses Intel's energy-efficient Core 2 Duo processor. Intel's tiny Atom processor is a marvel of low-power technology, and is or will be used in subnotebooks (Asus Eee PCs) and mobile phones (future iPhones) alike. And the company is working on several generations of increasingly power-savvy processors, including projects code-named Calpella (based on Intel's Nehalem microarchitecture) and Moorestown (the Atom's successor).