Can you Charge a Solar Light with Flashlight?

By Matt •  Updated: 02/24/22 •  7 min read

Solar lights use have increased worldwide. The sun is the primary energy source for solar lights and is free. However, the summer does not last the whole year. So how do you charge your Solar lights during the winter or if you live in a cold environment?

Sometimes the weather is unpredictable if you find that your battery is drained and there is no light. Use any of these ways to recharge your solar lights.

Solar Inverter
Solar Inverter
  • Electricity
  • Indirect sunlight and
  • Artificial light.

So can you charge a solar light using a flashlight? 

Can you Charge a Solar Light with Flashlight

A flashlight is an example of artificial light that you can use to Charge your solar lights. Using a flashlight to charge whole solar lights might come as a surprise. However, depending on the brightness, it is possible but relatively slow. 

Before you start to question the logic behind a flashlight charging a solar, let us explain how a solar lighting system charges. 

  • A solar lighting system has a solar panel has amorphous cells and photovoltaic cells that turn sun radiation into electricity. 
  • When the sun waves reach the solar panel, the panel collects the energy and wires it into the battery. This is what we call charging.
  • Energy from the sun is stored in the battery as chemical energy. A sensor on the panel detects darkness at night, and chemical energy is converted into electricity—the electric energy powers the LED bulbs to light up. The exact process repeats itself when daylight comes. 

Artificial light uses the same concept as sunlight energy. Charging using flashlights will be slower as it produces a low amount of Lumen. A bright flashlight produces about 100 lumens, while the sun produces 100,000 lumens. Even when on a cloudy day, the lumens produced are much more than those produced by a flashlight. 

Although the flashlight can charge up solar lights, it is not a practical method in the long run. You can try using a UV light instead. 

Can you charge a solar light with UV light?

A band of UV lights identified as UVA falls under the Red visible light spectrum. A portion of the band charge solar lights but is not as effective as the sunlight or artificial light. 

The red light spectrum, where most UV lights fall, is too low to Charge a solar battery. Their wavelength range is usually 100-400mn. But the wavelength range that is sufficient to charge a battery between the Red-violet wavelength range is about 380- 759mn.

Ways to Charge Solar Lights Indoor

Solar light is an effective way to light your garden. It is cheap and adds to the ambience. During the winter, the solar panel is placed indoors. This is to prevent moisture from destroying the solar panel. Also, there was less to no sunlight at that time. So how do you charge your solar lights indoors?

1. Charge your Solar Lights Thorough the windows

Technically just because it is cloudy doesn’t mean there is no sunlight. 

When your solar panel is replaced on the windows facing the sun’s direction, this qualifies as sunlight charging. The sun will reach the panel indirectly. However, if the sun intensity is high, the battery will charge as usual.

 2. Charge using electricity

Electric charge is far much the best way you can charge your solar lights and solar appliances when there is no sun.

Most appliances have a USB outlet or an adapter directly connected to the socket. 

However, it would help if you refrained from charging your solar battery using electricity. Instead, it would be best to charge your solar battery using electricity only during emergencies like planning for camping or hiking.  

3. Charge using LED bulbs

LED bulbs are efficient ways to charge solar lights indoors. However, you might need to charge the battery for more than 15hrs for it to be fully charged.

Tips to Charge your Solar lights Efficiently

Using your solar lights when there is less sunlight might cause the battery to drain. When the battery is drained frequently, it reduces the lifespan of your solar lights. 

To curb that issue, we will give you three tips you can use to charge your solar lights efficiently.

  1. Keep the Solar Panel Clean

To make sure that the sun reaches the photovoltaic cells in a solar panel, clean the panel regularly. Debris and dust are the most common things that block the solar panel. 

  • A clean solar panel ensures the sensor is exposed. If the sensor is blocked by dirt, the bulb will stay on even during the day. This drains the battery and makes it last for a few hours at night. 
  • Use a microfiber cloth dipped in clean water. Or use a liquid that cannot cause streaking. Avoid detergents at all costs.
  1. Direct the solar panel toward the sun

Solar lights battery charges when directed towards the sun. 

The mirrors should be a bit larger than the panel to direct more sunlight.

  • Sometimes shadows and trees block the sun from reaching the solar panel. In that case, transfer the solar panel to open space. 
  1. Switch off the solar lights for 72 hours for complete charging. 

When the sun is not enough, the battery will not charge fully. When the sun detects darkness at night, despite the battery not being fully charged, the bulbs will light up. 

To prevent the battery from being damaged by frequent drains, switch off the solar lights for 3days until it is fully charged. 

Ensure that the panel is clean and placed in an open place for maximum sunlight exposure.

Frequently Asked Questions (FAQs)

Why do my solar lights go off at night?

Have you checked your solar panel status? A dirty solar panel might be blocking sunlight from reaching the photovoltaic cells. As a result, your battery is not fully charged. In addition, the solar panel might all be blocked by shadows. 

Another reason is that your rechargeable batteries need replacement. Solar lights battery can last up to 4 years without needing a replacement. If your batteries life span has depleted, change the batteries. Solar lights batteries are inexpensive.

What type of bulbs is the best when charging solar lights?

LED bulbs are the most efficient artificial lights for charging solar lights. This is because they have enough brightness and produce more lumens than other bulbs. 

Can fire charge solar lights?

Absolutely no. Solar lights cannot be charged using infrared UV light to charge. 

Fire does not produce a wavelength range between 380-750mn, which is the ideal range for charging solar lights.

Can I use heat to charge my solar light?

It is possible to convert heat energy into electrical energy.

Some solar panels convert sun heat into chemical energy stored in the battery until it is dark. The energy is then converted into electrical energy to light up the bulbs. These solar panels that convert heat into electricity are called thermal panels. 


Sunlight is the most efficient form of energy for changing solar lights. However, sometimes you have to get creative with your charging methods, especially during winter or cloudy days. 

Artificial lights can charge the solar light but are slightly slow. It will take more than 10hrs before the battery is fully charged. 

Electricity is another way you can charge your solar lights. Most solar batteries come with an adapter that can be connected directly to the power source. You should, however, use this method only when there is an emergency.

If the sunlight is back after a few cloudy days, ensure you charge your battery for three days before using them.


I’m Matt, a computer and electronic embedded system developer. Currently, working as an electronic engineer. In my leisure time, I do love to blog about technology stuff. Specially, new advance high tech devices. Portable solar systems are one of topic that I love to investigate. They are becoming more powerful day by day which keep me alert.