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How Does a Solar Watch Work?

Posted by Momentum Watches - February, 01

Learn how our solar-powered watches work.

how a solar powered watch works

How does a solar watch work?

A solar watch is a quartz watch with an added solar panel and a special, rechargeable battery. Solar watches have semi-transparent dials (faces), so light hitting the face of the watch passes through the dial and hits the solar panel behind it. The solar panel converts the light into energy, which charges the rechargeable battery in the movement.

The rechargeable battery acts as a “power reserve”, storing power, so that the watch will continue to run in the dark, without any light. When fully charged, the latest solar movements will run in complete darkness for 6 months or more.

“Solar” movements are light powered, so they do not need to be exposed to the sun. They will charge in any light, not just in sunlight. The brighter the light, the faster the watch will charge. Direct sunlight is very bright and will charge a watch fully in around 6 hours. Almost any light will still charge the watch in everyday use, just more slowly. In typical office lighting, under cloudy skies, or on a table under a bedside lamp, the watch will always be charging. Most users never need to consciously “put the watch in the light", finding that it is always well charged with everyday exposure to any kind of light.

The 7 key reasons why a solar watch might be the perfect everyday watch.

1. A Momentum solar watch saves you money, by making light work. It is charged by light, so regular battery changes are eliminated. This makes a Momentum solar watch like a perpetual motion machine, that just keeps on running. You can expect to save big bucks on the cost of regular battery changes and you will save even more on shipping costs, if you usually send in your watch for servicing. Our solar watches offer an unmatched low cost of ownership.

2. Convenience: while many modern quartz watches have a low-battery warning feature, the battery in a solar watch will almost never need replacement. This means your watch will not stop suddenly in the middle of a business trip, or the day before you leave on an extended hiking trip. (Our solar models even have a low charge warning, so the second hand will do a “double-step”, warning you to put it in the light, if the power is low and the watch needs charging.) Power reserves are so good that, once it is fully charged, you can leave a Momentum solar watch in a dark drawer for weeks or months and it will still be right on time when you take it out of the drawer to wear it.

3. Improved reliability and waterproof performance: most issues with a quartz watch happen after servicing. Opening a watch to change the battery will break the waterproof seal. We often see watches that have leaked because the back o-ring seal was not put back in place or was damaged on re-assembly after a battery change. If a watchmaker is not careful, small amounts of dust or dirt can get into the movement when a watch is opened, making it run less reliably, or even stop sporadically. Momentum solar models will almost never need to be opened, so the waterproof seals will stay intact making it more reliably waterproof and virtually eliminating any risk of getting any debris into your watch.

4. Fast charging: it only takes about 6 hours in the sun to fully charge your Momentum watch. Once fully charged, smaller models (VS22) will run for up to 6 months without any additional exposure to light. On larger models (VS42, VS43) with slightly larger batteries, the power reserve from a full charge is up to 12 months!

5. Power up in almost any light. While charging in direct sun is very quick, almost any office lighting, home lighting, or natural light on a cloudy day will also reliably charge your Momentum solar watch… just a little slower than direct sunlight!

6. Sustainability: While our service centers recycle used batteries, most places do not, so used batteries are usually thrown away. Your Momentum solar watch will eliminate regular battery changes, resulting in far fewer batteries ending up in our landfills. For many customers, with no good local watchmaker and nobody with a modern waterproof tester, watches need to be packed up and shipped off for service, so by making regular battery changes a thing of the past, Momentum solar models mean less packaging, less shipping back and forth and less impact on our environment.

7. Outstanding warranty: Our solar models are covered by our 6-year limited warranty, so in the unlikely event that the battery no longer holds a charge any time within the first 6 years, you are covered. (Of course, impact damage, band replacement, theft or normal wear-and-tear are not part of this warranty.)