Seiko started the trend two years ago with the splashy and successful introduction of its Kinetic series of watches. Last year, the Swiss watch giant SMH bought out its own battery-less technology, called Autoquartz, in the Tissot brand. SMH brands Omega and Longines followed this year with their own battery-less models, while Seiko has incorporated Kinetic movements into its new Arctura line. What's gotten into these brands? Read on.

by Norma Buchanan

- The wearer need never replace the battery.

- The watch will never stop unexpectedly the way a battery-powered watch will when the battery runs down.

- The wearer need not worry about any environmental pollution that could be caused by disposal of used batteries.

Battery-less watches are powered by the movement of the wearer's arm. That movement causes a weight to move back an forth, which sets a micro-generator spinning which produces electrical energy. The electricity is stored in a capacitor (analogous to a battery in a battery-powered watch).

From this point on, the battery-less watch functions as a normal quartz watch does: the electricity is transmitted to an integrated circuit, which keeps the quartz crystal oscillating at 32,768 Hertz. The integrated circuit sends impulses at one-second intervals to the stepping motor, which powers the gear train, which moves the watch's hands.

The major players are Seiko and SMH. Other companies are also experimenting with battery-less technology. Citizen makes a battery-less movement which it sells to Festina for use in its watches, but so far hasn't introduced it into the Citizen brand.

No. The terms "automatic" and "self-winding" refer to mechanical watches powered by a mainspring (not electricity, as in the new battery-less watches) and using an oscillating balance wheel (rather than a vibrating quartz crystal) to measure time. The only similarity between automatic watches and watches like Seiko's Kinetic or the Omega-matic is the rotating weight that creates the energy to make the movement work.

Basically. There are, of course, some variations in the technology used by the different companies. (Seiko, for example, filed 50 patents for its Kinetic movements). The basic principle, thought, is the same: an oscillating weight generates electrical power which is stored and released gradually to power the movement.

Not really. It's true these watches don't need to have their batteries replaced ( they are continuously recharged by light), but they do have batteries.

Yes. Both use a quartz crystal as an oscillator, and it is the type of oscillator used that determines a watch's accuracy (in a mechanical watch the balance wheel serves as the oscillator).

No. Battery-less watches store electricity so they can keep running when they are not being worn. If the watch is fully charged when it is taken off, it will continue to keep time for between three and 14 days, depending on the watch brand and model.

Companies are working on ways to increase the length of time battery-less watches will run without being moved. Seiko has just introduced a Kinetic movement called the 1M which it claims will run for three months.

Yes. Battery-less watches have a power reserve indicator that shows how long the watch will run once it is removed.

The mechanisms vary from brand to brand and model to model. In Seiko Kinetic models, the wearer pushes a button and the seconds hand moves to indicate how much power is left. The hand will move through a 30-second arc if it is fully charged. If it moves less than the full 180 degrees, the watch is only partially charged.

Some watches also have a warning system to alert the wearer that the power is running low. In Seiko Kinetic models, for example, the seconds hand moves in a jerking motion at two-second intervals to indicate that the watch has only a few hours' worth of power remaining.

You can start a battery-less watch by moving it vigorously. This action gets the rotor spinning, generating electrical energy. Once you've done so, the ordinary motion of your arm will be enough to keep the watch working. Manufacturers have also deviced other ways to start the movement once it has run out of power. The Omega-matic, for example, can be repowered by winding the crown, which generates electricity.

That a tough question, and opinions within the watch industry are clearly mixed. Seiko is putting enormous emphasis on its Kinetic technology; placing it at the center of its marketing campaign. SMH, which actively promoting its battery-less watches, is making less of a fuss about them than is Seiko.

Proponents of battery-less watches cite Seiko's success with Kinetic as a reason to expect battery-less watch to one day eclipse battery-powered ones. Skeptics point to ever-longer battery life -- some lithium-iodine batteries last 20 years-- when they question whether the advantages now offered by battery-less technology will one day become negligible.