How Does a Solar Powered Watch Work – Step by Step

Solar powered watches! Remember how popular they were with our grandpas? Those 1970’s models are long gone, but today’s era is blessed with solar watches with newer technologies. Now they don’t have a pair of solar cells above the dial. Now those solar cells hide underneath the dial and make our watches look classy. And now the solar watches look precisely same as battery powered watches.

The solar watches are very convenient to use. They don’t suddenly stop one day while showing time like regular watches. As long as they are regularly charged, they can live up to a long time.

Though these watches have gained a lot of popularity, a lot of people still do not know how these function. It doesn’t hurt to gain knowledge, right? Then keep on reading!

What is a solar powered watch?

The answer to this question is easy. The watch that uses solar energy to show time and date is a solar powered watch. It merely uses a solar cell to convert light into electrical power to run the watch.

powered watch

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Regular watches run with the power gained from batteries. So, when the total stored energy of the battery is over, you have to buy another battery for your watch. But solar watches are different. They don’t require you to buy a new battery every six months. They can live up to 6 or 8 years if maintained with care.

During the 70s’, solar watches were first introduced to the people. Since then, tremendous improvements have been made to them. The first ever solar watch was the ‘Synchroner’. Roger W Riehl invented it. This watch had the solar cells on top of it and LED display on the sides that showed the time. That watch really had a terrifically impressive style.

How does a solar powered watch work?

The basic operation of a solar powered watch is no different than powered ones. The only difference is that regular wristwatches directly use the battery stored electrical power and solar watches use light power and then convert it to electrical power.


In an old solar watch, you might have seen the solar cells right above the dial or on the dial itself. Light powered watches of these days are different. They don’t have the solar cells exposed as they had before. Now, most of the watches have solar cells built-in under the dial of the watch. They can do from under the dial what they used to do when they used to be placed over the dial.

If you think that a solar watch only uses the sunlight and so you cannot use it at night or on a rainy day, you’re wrong. You can charge up those watches with artificial lights too. Even your bedrooms fluorescent lights can charge up the cells of a solar watch. Surprised, aren’t you? But I’m not kidding. This is the truth!

The solar cells are also mostly made of photovoltaic cells or PV cells. These cells absorb light and turn it into electrical energy; this effect is called photovoltaic effect, and so these are photovoltaic cells. Semiconductors are the basic components used for making PV cells. Each solar cell of a light powered watch has two layers of silicon which are a semiconductor. One of these two layers has missing electrons, and the other one has electrons more than necessary.

Let’s see how these watches work.

  • Moving of the electrons: 

When a solar watch is exposed to sunlight or any other kind of artificial light, the particles of the light hits enters through the dial of it. The layers of the solar cell absorb the energy of the sunlight.


The photons of light hit the deficit layer. The deficit layer already lacks electrons. The electrons of the deficit layer absorb energy from the photons of light. When the electrons of a particle absorb power, they start to shift to the upper layers of the atom. So, absorbing the energy from the photons, the electrons move to the surplus layer. The deficit layer again lacks the electrons then.

  • The flow of electricity:    

To store the charge, a wire is attached to the surplus layer to a rechargeable battery. The deficit layer’s electrons reach the surplus layer. The electrons keep flowing to the surplus layer. When the surplus layer has more electron flow from the deficit layer, a flow of electricity occurs. The wire then transfers the electricity to the battery. There’s another wire which transfers the used and extra electrons back to the deficit layer again.

Regular watches do not have this type of electricity flow. They have batteries that are pre-charged. But in a solar watch, it gets that electricity flow right over our skin and stores it. The whole process is kind of cool. And more than that, it is brilliant.

  • Storing the electrical charge: 

The battery saves the charges in it. It keeps on storing the charge in it. Most solar watches possess an overcharging cut-off feature. So, you don’t have to worry that the overcharging will cause damage to the battery but you have to if your watch doesn’t have that cut-off characteristic.

All the solar watches do not have that characteristic. So, yes, the battery can be damaged if you charge it too much. You have to be careful. The batteries of the solar watches generally have a lifetime of 6 to 8 years. But if you overcharge them frequently, the lifetime of them can lessen.

If you keep the watch for 6 hours under bright sunlight, you are all set for using the watch for a week without the need of charging it again.

If we consider the electrical charge in battery-powered watches, we see that, once the battery’s charge is over, you store charge in it again the way you do with solar watches.

  • The continuity of the circle: 

Some of the used electrons are moved to the deficit layer again to use solar energy again. And the rest is stored in the battery as electrical energy. So, again the electrons of the deficit layer get energy and move to the surplus layer, and some of them make the flow of electricity, and some of them return to the deficit layer again. The process continues till the battery gets charged fully.

Though you can charge the battery via artificial lights, you need to check out the lux intensity. The more the intensity, the less time it takes to charge the battery fully. For instance, charging the battery in with sunlight which has a luminance of 100000 lux, it will take only 6 hours to charge the battery from empty to full.

If you want to charge with artificial light, I suggest you should consider placing the watch near to a light source. This is because the lux intensity reduces as you increase the distance. So, if you keep the watch close to a light source, it will take less time to get charged. But if you think you won’t do this one too, let me warn you that this will take a lot of time to charge the battery fully!

When you are at home or office, and you are not so close to a light bulb, it will take a lot of time to charge the solar watch. Apparently, that is between 150 to 350 hours for most of them.  However, if you keep the watch close to the artificial light source, it will take less time than that. But, under bright sunlight, it will take only 6 hours to charge the battery to full. And believe it or not, most solar watches can reserve this charge for up to 6 months without needing to get charged again.

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Though a little inconvenient sometimes (on a rainy day), a solar watch can be extremely reliable. It won’t stop ticking if the battery loses the charges once. It can be recharged again. But regular watches don’t work this way. Once they stop, they stop until a new pair of batteries is inserted.

But you have to be careful about the solar watches. You cannot leave them for a long time without charging them just because it has a battery life of eight years. You need to get it charged once in every six months if you don’t use it. Otherwise, the battery life will degrade and the watch will be out of order before it even reaches its lifeline.

If you are someone who is too lazy to charge the watch for 30 minutes in a couple of days in the week, I might have an easy escape for you. You’ll find solar chargers in online and local stores. You can have them charge your watch without the need of charging it under sunlight. It will cost you a couple of bucks, but it can be worth the time you are saving.

So, this is how the solar watches work. I hope all your confusions and questions about these watches can go away now after reading this piece.

Team Chooserly

A passionate blogger! Editor at Chooserly, and a regular author at HuffingtonPost, LifeHacker & Forbes!

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