How to Charge Solar Lights Without the Sun

by Malcolm Woods

Direct sunlight is not always available, but that doesn't mean you can't still charge solar-powered lights. I'll show you different ways of charging solar lights without the sun.

Without the sun, life wouldn't be possible on earth. The sun is the primary source of energy for us all.

Apart from making the growth of plants possible to feed us, the sun helps us reduce our utility bill and save the environment by reducing our carbon footprint.

But when the clouds come out and the sun say "ciao!", many people think that solar power is out of reach.

But is it? Not true!

Though at inefficient rates, solar power collection is possible in conditions of indirect sunlight.


Let's find out.

Charging Solar-Powered Lights Without the Sun

 Charging Solar-Powered Lights Without the Sun
Charging Solar-Powered Lights Without the Sun

When it comes to this, there are two main questions:

  1. Way to charge indoor solar lights
  2. Way to charge outdoor solar lights

Let's look at the answers.

How to Charge Indoor Solar Lights

Charging indoor solar lights relies on one thing - regular incandescent lightbulbs.

I have done this many times.

As an adventurous guy, I like to visit places like caves and the woods. And sometimes I find myself in the dark. My solar flashlight comes in handy.

But sometimes I remember that the flashlight is not charged on the eve of the day when I am making such trips. In that case, I have to rely on the artificial lights in my house, and it is not once or twice that those flashlights have saved the day (I should say the night!).

How do I do it?

I put the flashlight beneath the lamp in such a way that the solar panel faces the light. I let the light remain on till morning, and on many occasions, I find the battery more than halfway charged.

As for positioning, I place the flashlight around 20 inches away from the light source. I also make sure there are no obstructions in between.

How does that work?

You see, the photovoltaic cells in solar panels respond to light from incandescent bulbs in a way a lot similar to how they react light rays from the sun.

That's because both the incandescent bulbs and the sun put out light waves that can be converted into energy.

That said, it is important to note that efficiency is not the same. You see, the UV rays from the sun are a lot stronger than the low-dose UV radiation from incandescent light bulbs.

Moreover, bulbs require power to make power while the sun does not.

That is why it takes more time to fully charge a solar-powered light under an incandescent bulb.

While it takes 5 hours to charge my flashlight to full capacity under the sun, it takes around 10 hours to do the same under an incandescent light bulb.

Tip: if possible, use a bulb with a higher wattage. A 100-watt bulb will charge faster than a 40-watt bulb.

What sort of bulbs can I use to charge solar panels?

As long as the light produced is in the right spectrum (UV), you could use any kind of bulb.

There are three options when it comes to light bulbs:

  • LED
  • Incandescent bulbs
  • Halogen

LEDs produce light in a diffused fashion such that it is dispersed in different directions. That's a bit of a problem because it makes it hard for the panels to capture the light.

Incandescent and halogen lights are more focused, which makes it easier to capture the light.

While artificial lights produce light in the right spectrum, UV, they don't produce it as abundantly as the sun does. That is why they're not as efficient as the sun at charging solar panels.

Some people prefer to use UV lamps to charge solar panels, as they're more efficient than other lights.

Note: however, that UV lamps use more energy, and that increases the power bill.

How to Charge Outdoor Solar Lights

Normally, we use direct sunlight to charge your solar-powered items. But sometimes, that is not available. Maybe it is cloudy, or even worse, maybe it is winter.

Let's see how to handle each of these situations.

Charging them when it is cloudy

On a cloudy day, sunlight still reaches us, though it is filtered by the clouds.

Note: there are various types of solar panels, including polycrystalline, monocrystalline, and amorphous panels.

While others feature normal designs, the amorphous solar panels feature a design that ramps up the light-capturing function. These are built for the shadowy and cloudy areas.

So, I would encourage you to get amorphous panels if you live in an area that is often cloudy.

And while charging, try placing the panel in the place that seems to get more light.

Charging in winter

Charging your solar powered lights outdoors is a challenge during winter, as the clouds cover the sky most of the time.

You can still charge the lights because even though there are clouds, the ultraviolet rays are still coming in and hitting the ground.

The biggest problem with collecting energy from the sun with solar panels during winter is not even that direct sunlight is not available. It is rather that the snow can cover the panels, obstructing them and making it impossible to collect energy.

But the problem is that charging will not be very quick or efficient, as the rays are getting filtered.

How to improve the rate of charging

There are a few things you got to do to improve the rate of charging:

  • Place the panels such that they face the south as that is where most light comes from during winter.
  • Clear the snow from the panels regularly to remove obstruction - you can use a small soft-bristle brush and a cloth to remove the accumulated snow.
  • Keep relocating the solar panels to remove shadows.
  • If you have solar panels that can tilt or swivel, try repositioning them throughout the day. And especially at noon when the direction of the incoming sun rays shifts.

Charge Solar-Powered Items Without Direct Sun

Other Ways You Can Charge Solar-Powered Items Without Direct Sun:


Some of the best solar lights come with more than just one option for charging. Some can be charged with electricity as well.

These usually come with a USB slot, so that you can plug them directly into a wall socket or even your car charger.

Such products can be a lifesaver, especially where you find yourself in an emergency situation. You may find that you forgot to charge the solar flashlight, and you're already in the car headed for the camping site.

In that case, you can just plug the flashlight directly into your car's DC charger.


Maybe the solar panel of the light or device you want to charge cannot be taken outside due to limits in the length of the solar cable.

What about the windows? Can you place the solar panel near a window so it gets the light coming in through the window? Try it.

Personally, I use this strategy sometimes, and it works. I place a small mirror on the outside, and it reflects the rays of the sun, projecting them onto the solar panel. This improves the charging efficiency.

Final Word on Charge Solar Lights Without the Sun

You have your answer now - yes, you can charge your solar lights without direct sunlight. These other methods are not as efficient as direct sun rays, but they can be a lifesaver.

As you've seen, there are several ways of doing it. You can use the artificial lights in your home or even electricity if your device allows it.

If you're using artificial lights, keep it in mind that the more the wattage, the higher the speed and efficiency of charging.

You can also charge through the window and use mirrors to redirect the rays of the sun. The secret to charging solar-powered items in cloudy conditions is to ensure there are as few obstructions as possible. It also requires repositioning the panels often to capture as much light as possible.

About Malcolm Woods

Malcolm Woods is a blogger who enjoys writing about technology and solar power. He has a passion for learning new things, and loves to share his knowledge with others. Malcolm is also an advocate for sustainable living, and believes that everyone has a responsibility to do their part in preserving our planet.

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