What kind of light will charge a solar watch?

By Matthew Joseph Nandirio •  Updated: 10/18/21 •  8 min read

You might feel trouble charging your solar watch without natural sunlight. Fortunately, this problem can easily be resolved! Let us proceed forward to know the ways!

Maybe the place you live in does not have enough exposure to the light of the sun to charge a solar watch. Maybe at the time your need to charge your watch but unfortunately it is dark outside. No light is entering your room also. 

Solar Inverter
Solar Inverter

Although solar watches are genuinely relatively easy to charge with the direct light of the sun so often people can get in positions wherein they do not have daylight to recharge their solar watch. That is in which alternative mild options are available.

Your solar-powered watch or clock can be charged interior by way of the light from an incandescent lamp or fluorescent lamp. However, it will take a much longer time than charging it with the light of the sun.

For wall clocks and alarm clocks, charging utilizing a fluorescent lamp is the most efficient manner. Avoid charging such clocks beneath direct sunlight, as doing so might damage your favorite clock.

Will a light bulb charge a solar watch?

Yes! You can charge a solar watch with a light bulb. Unfortunately, it is not always an ideal approach. LED bulbs generally convert at best 20%-30% of the light into power. 

You can use a high-wattage bulb. It is a good thing to do. On average the solar generates 1000W of electricity consistent with a square meter on this earth. You might not expect a bulb to produce that form of electricity. In that case, you can use an LED bulb available containing high watt. 

Charging a solar watch with a light bulb, or every other artificial light is not as powerful in comparison to the light of the sun.

Will led the light charge a solar watch?

The answer to the above question is yes! LED light can charge your solar watch. the sad part is, it isn’t as effective as the light of the sun. It also does not do fast charging. It is better if you try to keep away from charging the watch with LED light unless you’re in a very critical condition.

Let us now discuss the steps that you need to follow-

Step 1: It is kind of the same as charging your watch with natural daylight. At first, test your watch’s indicator to make sure it needs the charge.

 Step 2: After that place the watch near your LED light. Do remember that smaller LED bulbs are pleasant. It is so because they’re most secure for your solar watch. 

 However, regardless of what LED supply, you select you need to place the watch at least 20 inches from the light supply. Then start the charging process. This distance will hold your watch from potentially being damaged through the LED source.

 Whatever we say but the most efficient and safe manner to charge the solar watch is with natural daylight. You should try to avoid doing it continuously. Or maximum of your time. Your watch may be more secure and remaining for a long period.

 Light time required to charge fully

Source of the lightCharging time (until full battery)
Natural Sunlight (full sunlight)20 hours
Natural Sunlight (cloudy weather)60 hours
LED Light (artificial)150 hours

Will a flashlight charge a solar watch

The flashlight would charge your solar watch. But as I have said earlier that it would not be as good as natural sunlight. You should also remember several things. 

30W-fluorescent lamp or light would provide about 10000lx. It should be kept 5cm apart. Then again 30W-fluorescent light source would provide about 3000lx. It should be kept 20cm apart. 


1. You are requested to study the manual. You can know what is exactly inside the solar watch? Usually, manuals have information concerning that. If you are not able to find it within the guide or if they do not include it then you have to go and search on the internet. Finally, open up the watch and extract the battery on your own.

2. You can simply put the watch anywhere in your house. But make sure there is a minimum passage of light. It’ll slowly absorb the light they need from the out of doors. As well as internal of home. For example – bulbs, lamps, LEDs, and many others. This may take quite a good amount of time but the best thing is you can utilize its several capabilities.

3. It is a common phenomenon that we all want to charge fast. If you want to do fast charging as well as want to control the temperature then there is an easy way. Let us check it out.

At first, you need to place the watch inside a clear bag. You need to put the box inside a container that contains freeze water. 

After that step, you need to put the box beneath the light that you have placed. Here the water will be like a sink for the heat which is generated within. It would also abstain the internal system from getting hot fast.

4. You should not use metallic halide in order to charge your watch. A LED bulb of small size or a UV lamp which have less intensity can assist in charging the watch more safely. Though the cost needed to do so will be higher. As well as the money will be needed more. 

5.  Do you have any idea about soft light? Or you are thinking what soft light is! A soft light normally produces much less warmth and much more light which is interesting. But do remember that the heat produced simply kill your watch.

The interior parts of your watch is build up from sensitive elements.  Unfortunately, this light would create great harm to your watch.  

Did you ever think about the heat that is produced while charging it?  The interior part of your clock will conduct the warmth that is created. 

The unexpected increase of the heat can either enlarge the components or melt them. The extended parts would not be able to preserve their authentic shapes. For that reason, the watch you are using will not function properly. As an example, you could somehow be able to watch the display portion but it is going to be in a very blurred condition.

6. Maintaining a proper distance is very important. Hold at the right distance between the power supply and your watch. In case you maintain the distance very low in a motive to charge the watch quickly, then I am afraid to say that you are doing the wrong thing. 

The warmth can damage the polarizing film of the watch and can bring about permanent damage. In addition, if you focus a small light source via a lens onto the watch’s sun panel then it will deliver even worse effects faster.

Will a solar watch charge on a cloudy day?

Definitely yes! It would get a charge but before going to that topic let us discuss another important topic. 

Luminous Flux is an important term to understand the whole issue. So what it is actually? It is the entire amount of light found in a place.

This implies that LUX is the depth of the overall amount of seen light in keeping with the unit area. Your solar watch wishes the perfect quantity of Lux to get charged. By any chance If lux is low then the watch will get charge somehow but it will be way too slow. 

On the other hand, if the intensity is high then it’s also problematic. The watch will be charged but there would be a high chance that it might melt. 

Just imagine a brilliant sunny day. You just step out of your home and mark a one-meter square location at your ground. This 1square meter box has an intensity consist of 50,000 lux.

The same thing on a cloudy day will be of 5000lux inside your house. Therefore you can understand that you would get the opportunity to charge your watch but its efficiency would not be like the sunny day. 

Final words

Solar watches are a beneficial machine that can hold time without using any batteries. It only needs a simple thing and that is solar power. But the question arises if you do not get the amount of light required from the sun. In the whole article, I tried to resolve the issue. 

Some issues will bother you. Thus, if you ever make any plan to use an artificial source other than sunlight then be carefully about taking the right precautions.

So without any delay notice your watch and take the necessary steps!

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Matthew Joseph Nandirio

Matthew Joseph Nandirio is the Founder of walkingsolar. After graduating from the University of Houston in 2002, matt started working as an electrical and electronic engineer for several multi-national solar energy companies. He has a wide range of experiences including solar system requirement analysis, planning, maintaining, debugging and even solar device development through research. He now shares his 20 years of expertise through his articles on the walkingsolar website. Further, he is also the author of two books on Solar Technology, “Solar Power for Villages” and “DIY Solar System for Dummies”.