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Why Do Solar Lights Need Batteries?

A few months ago, I had an electrical failure in my home while I was preparing a barbecue with my family. At first, I did not panic because I figured my outdoor solar light would come on automatically in a few seconds.

Why do solar lights need batteries? Solar lights require batteries to store the electricity generated during the day for use later on.  

Why do solar lights need batteries?

Solar lights work well with solar cells that can keep them operational until they die in a few months up to a year. When shopping for batteries for solar lights, it is essential to understand the type of cells to buy and how to dispose of used solar light batteries.  

Why Solar Lights Need Batteries

Many people often wonder if solar lights require batteries because they use the suns energy to stay on. Well, solar lights are designed to convert the sun’s energy into electricity that powers the lights.

During the day, the lights do not necessarily need batteries because they can instantly convert the sun’s energy into electricity. You do not necessarily need batteries for your solar lights to work during the day.

You probably do not need to use solar lights during the day because the sun provides enough light for us to use. Therefore, you need a way of storing the suns energy during the day so that you can use it when you need it, at night.

Many solar lights come with:

  • Rechargeable batteries to store the sun’s energy during the day.
  • The batteries are standard features in most electronic appliances and gadgets ranging from watches to cameras.  

Types of Rechargeable Batteries

  • There are different types of rechargeable batteries on the market, each with its pros and cons.
  • Rechargeable batteries are not the same; some provide lasting battery life than others.
  • Rechargeable batteries have electrons that store and release energy when required.

Lithium-based batteries

Like smartphones and laptops, many solar lights on the market feature lithium-based batteries. Users often prefer solar lights with lithium-based batteries because their energy density is almost twice as high as nickel-based batteries.

 Lithium-based batteries save space because you can get one 3.6 volt battery pack instead of several 1.2 volts cells joined in a series. Their space-saving feature is a considerable advantage in solar lights where you do not need many smaller batteries packed next to each other.  

Nickel-based batteries

Cheaper solar lights often come with nickel-based batteries. Nickel-based batteries can be put into two main categories:

  1. Nickel-cadmium
  2. Nickel-metal hydride

Nickel metal hydride batteries have a few advantages over nickel-cadmium batteries. For starters, nickel-metal hydride batteries are:

  • Affordable
  • Eco-friendly
  • High capacity

 If you are going to use nickel-cadmium batteries, it is essential to know that cadmium is highly toxic and should not be left near children or pets. In addition, it is harmful to the environment if not correctly disposed of.

Cadmium batteries are still available on some devices including some solar lights. Some manufacturers prefer to use cadmium batteries because:

  • They provide optimum discharge rates
  • They have lower self-discharge rates, which is the rate at which batteries lose charge due to non-use.

However, for many users, the advantages of cadmium batteries are outweighed by the fact that they are not suitable for the environment.  

Using Non-Rechargeable Batteries in Solar Lights

It is advisable not to use standard non-rechargeable batteries in solar lights.  Some people may be tempted to use non-rechargeable batteries lying around their homes in their solar lights. However, solar lights are designed to work with rechargeable batteries.

When you put non-rechargeable batteries on your solar lights, the light will try to recharge the batteries. Although non-rechargeable batteries can handle a small degree of recharge, prolonged recharge will cause them to explode. The explosion of the battery may ruin your solar lights or leave you with a lot of mess to clean up.  

Meaning of mAh in Solar Light Batteries

You have probably seen the abbreviation mAh in solar light batteries. mAh stands for milliampere-hours, which is a measure of the length of time a battery will last when fully charged.

Contrary to the common misconception, your solar lights will not be brighter or stay on for longer if you use a higher mAh value battery. Exposure to sunlight determines how long your lights can stay on.

For instance, if your solar lights are designed to work with 500mAh batteries, they will not stay on for longer if you use 800mAh batteries. Solar light batteries are designed to store as much energy as they receive from the sun. However, a higher mAh battery has the potential to provide longer battery life for each charge.

How to Dispose of Used Batteries 

 Used solar light batteries can be harmful not just to the environment but also to pets and people. Therefore, dispose of used solar cells properly.

There are many battery-recycling centers in the U.S. Research battery recycling centers near you. Alternatively, many stores that sell electronic hardware have battery recycling points that you can use to dispose of used solar light batteries.

Things to Look for When Buying Solar Light Batteries


The capacity of solar light batteries varies depending on the model. The length of time solar light batteries will remain charged is determined by its capacity. High capacity batteries often last longer before the next recharge. Consider choosing batteries with high capacity ratings. The best way to know the capacity of solar light batteries is by checking its mAh ratings. The higher the mAh, the higher the solar light battery capacity.


Solar light batteries do not have fixed prices. Their cost is determined by various factors, which vary from one manufacturer to another. Set a budget for solar light batteries and buy batteries whose prices are within your budget.

Expensive solar light batteries do not necessarily provide optimal performance or durability. Today, there are affordable solar light batteries on the market that last long and perform exceptionally.


There are many types of solar light batteries, including:

  • Lithium-based
  • Nickel batteries

It is essential to use batteries that are specifically recommended for your solar lights. Many solar lights use between one to four batteries. Consider using solar light batteries that can provide optimal performance and last as long as possible.

This article is owned by and was first published on September 5, 2019

Memory Effect

Newer solar light batteries charge to full capacity with each recharge. However, the same cannot be said of older nickel-cadmium cells mostly due to a phenomenon known as cyclic memory effect. Unlike nickel-metal hydride batteries, NiCd batteries “remember” their lowest points of recharge and often reset their capacities to match the last low level.

To illustrate, let’s say you have charged your solar lights with NiCd batteries to 90 percent. The next time you recharge the light, it will charge up to 90 percent only instead of full capacity. This is what the cyclic memory effect means.

Effects on the Environment

Some solar light batteries, including nickel-cadmium have detrimental impact on the environment. Cadmium is a heavy metal that is considered highly toxic. Although used sealed batteries may not pose any harm, open and leaking batteries require extra attention during handling because they can be poisonous. Cadmium can be absorbed into the body when it comes in contact with the skin.

It is advisable to dispose of used solar light batteries in recycling stations. Solar light batteries can be harmful if they end up in landfills or water bodies.

Solar lights need batteries to store up energy from the sun. There are many types of solar light batteries, including lithium-ion and nickel-based batteries. When shopping for solar light batteries consider their price, environmental impact, memory effect, capacity, and type.

This article is owned by and was first published on September 5, 2019

Title image by Ken Whytock

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This article is owned by and was first published on September 5, 2019

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