Technically speaking, solar lights do not run on solar energy. They run on electric energy stored inside rechargeable batteries that, in turn, are recharged using miniature solar panels.
Semantics aside, you need to have the right batteries in your solar outdoor lights if you want them to provide you with illumination throughout the night. To help you determine what types of batteries for solar lights you should use, this article will supply information about your choices.
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What Kinds of Batteries are Used in your Solar Lights?
These days, solar lights can use several types of batteries – with each one having their shares of pros and cons. You should weigh them against each other using your preferences. This will let you know which battery type is the best for your solar outdoor lights.
1. NiCad (Nickel Cadmium) Batteries
Nickel Cadmium (NiCad) batteries were once the most popular type of rechargeable batteries. They hit the peak of their popularity in the 90s. NiCad batteries come in similar sizes to alkaline batteries, which is why they are the most popular choice when it comes to powering portable devices.
One advantage that NiCad batteries have over alkaline batteries, aside from being rechargeable, is that they do not suffer from significant voltage drop when their charge gets low.
NiCad batteries’ voltages even pretty much remain the same until they are fully discharged compared to alkaline batteries with voltages that can drop to as low as 0.9 volts as the battery discharges.
2. NiMH (Nickel Metal Hydride)
NiMH (Nickel Metal Hydride) batteries have taken the throne from NiCad batteries as the most popular battery type used in solar lights and general use as well. This kind of battery was invented in the late 1960s but it was not until the late 1980s that they became commercially available.
These days, most solar lights use NiMH batteries because they are cheaper, hold more electric charge, and are much easier to dispose of without harming the environment. You can also find NiMH batteries in the same sizes as alkaline batteries, which means you can find those that you can use for solar lights.
3. Li-ion (Lithium Ion)
These batteries were first conceptualized during the mid-1980s but were only made commercially available until the 1990s. Li-ion batteries are still extensively used today as the power source of smartphones, tablets, laptops, and other portable electronic devices.
Since Li-ion batteries can also come in different shapes and sizes, including those used by alkaline batteries, you can find many brands of rechargeable Li-ion batteries in the market. What makes Li-ion batteries better than NiMH is that they only take half the time to fully recharge.
However, they are a bit more expensive. Furthermore, there have been issues of some Li-ion batteries overheating and catching fire. This was notoriously made public when the batteries of the infamous Samsung Galaxy Note 7 started unexpectedly catching on fire.
The issue with the Samsung batteries was localized to the phones only, though, and other kinds of Li-ion batteries do not have the same problems.
4. LiFePO4 (Lithium Phosphate)
This is a variant of Li-ion batteries. It is considered as a highly improved version. These batteries have even smaller voltage drops compared to Li-ion batteries, which makes them less reliant to the voltage regulating circuitry. They have such uniform voltage outputs that you can place them in series without any problem whatsoever.
When used in solar-powered outdoor lights, LiFePO4 batteries can make them emit brighter lights. They can also sustain their brightness longer, even when their charge is almost zero.
Buying Guide for Rechargeable Batteries for Solar Outdoor Lights
Rechargeable batteries might not be that expensive. However, if you will be replacing the batteries of all your outdoor solar lights, the costs will add up. This is why you need to be wise when shopping for batteries.
You do not want to waste your money on batteries that did not even come close to what you were expecting. To help you with your search, here is a quick buying guide. Check if the following qualities are present in the batteries that you are thinking of buying:
The Right Size
Before you even go out shopping for batteries, check the size that you need to buy. You will be surprised to find out just how many people have made the grave mistake of buying the wrong size batteries for their solar lamps. You do not want to walk back to the store then sheepishly ask for replacements because you accidentally bought the wrong size.
You need to open the battery compartment of one of the solar lamps and check out what size of batteries they use. To be on the safe side, bring one of the depleted batteries with you when you are out shopping,
Usually, outdoor solar lamps use AA or AAA batteries and since they are almost similar in size, people often mistake them for each other.
The Right Type
There are several different types of batteries that are used for powering solar outdoor lights. These batteries differ in chemistry and composition and they have their own sets of advantages and disadvantages. Choosing one type over the others will be up to your personal preference.
NiMH (Nickel Metal Hydride) batteries are the most commonly used and the most economical choice. However, take note that they also do not last quite as long as the other battery types. The good news is that they are more affordable.
NiCad (Nickel Cadmium) batteries are the pioneers in rechargeable batteries, and they have evolved quite a bit since they were first introduced. However, they still have problems regarding charge memory. This means that NiCad batteries need to be discharged completely before they are recharged.
If you recharge them when there is still around 20% of charge left, the battery will “remember” the amount of charge it received. This means that the next time you recharge the battery, it will only go up to 80% of its original capacity.
Li-ion (Lithium Ion) batteries are probably the best choice when it comes to rechargeable batteries as these have very negligible voltage drops. This means they can consistently provide the same amount of voltage output regardless of the battery charge level.
Furthermore, lithium-ion batteries last longer than NiMH or NiCad batteries, often able to survive more than 1,500 charge-discharge cycles. The important thing to remember when buying rechargeable batteries is that you should not mix and match batteries.
If you choose to use NiMH batteries, only use those in a single battery compartment. Do not use NiCad batteries with NiMH batteries. Their uneven discharges might cause one or both of them to vent and leak.
Get the Right Battery Life
Battery life (especially in smaller batteries, like the ones used in solar lights) is measured in milliamp-hours (mAH). When shopping for rechargeable batteries, look for the ones that have the right amount of battery capacity. You can tell by the number of milliamp-hours that they have.
Usually, rechargeable batteries used for solar outdoor lights have a maximum battery capacity of 2,000 mAH. Solar lights use LED lamps so they do not use that much electricity at all. With that in mind, you can get by with getting medium-capacity batteries, something like 800 maH each will be fine.
This is preferred because lower-capacity batteries are easily recharged using solar panels. Low-capacity batteries can be fully charged using the small solar panels in the solar outdoor lights.
When Do You Need to Replace Batteries?
Typically, a rechargeable battery can last up to 1,000 charge cycles. This is equivalent to 1,000 days in terms of solar outdoor lights. This means that you need to replace your solar power lamps’ batteries every two and a half years or so. You can also consider replacing the batteries when you notice some of the lights start to turn off earlier than usual.
Do You Have to Replace All of Them at Once?
Ideally, yes. If one outdoor lamp’s batteries need to be replaced, odds are that the others will be following suit soon. Replacing the batteries all at the same time will somehow ensure that they will all deteriorate at the same time.
Moreover, buying batteries in bulk will save you more money. Plus, you will be doing the replacements in one go, rather than replacing batteries every couple of days.
Conclusion
You might have thought that you can use just any old battery to power your solar outdoor lights. Now you know the answers to what types of batteries for solar lights you should use and their sets of pros and cons, you can choose wisely which one is appropriate enough for you.
Although rechargeable batteries are not the cheapest, they are a good investment, especially considering that you will not be using any electricity from your home to recharge them. Don’t worry about the cost. When you get the best rechargeable batteries that you can afford, they will pay for themselves in terms of savings in the long run.
Hi, I am Eddie, Cleanenergysummit’s content editor. It’s so much joy to work alongside Justin, as the idea of providing knowledge about using clean energy excites us.
I’ve been working to address any concerns or questions you may have as you transition to using solar electricity to power your home. Tune in to hear our advice and suggestions on anything clean energy. Welcome!