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Perhaps you bought some solar lights, and they aren’t staying lit long, or maybe you are thinking about buying some to decorate your yard. Either way, it’s reasonable to wonder how long the lights will last.
How long solar lights last depends on either the type of battery or its solar panels. The LED lights are rated for at least 10 years, so those are rarely a problem. You can make a solar light last longer by changing the battery type. However, you cannot do anything about the solar panels.
A solar light consists of a light, battery, solar panel, controller, and problems with solar lights typically due to the battery. Proper maintenance can lengthen their lifespan somewhat, but if you want a light that will last more than 3-4 years, you will need to invest in a high-end light. Read on to learn more about how solar lights work and what your battery choices are to make them last longer.
Summary of the Article
How Does Solar Lights Work?
To light up your yard, solar lights use four components. They are
- A light source like LEDs,
- Photovoltaic Arrays – which captures sunlight and a converts it into electricity stored in a battery
- Controller – A controller sends power from the solar cells into the battery.
- Battery – Stores the energy
Read on to know more about how solar lights work.
Solar lights use LEDs and not only because they are small. LEDs are more energy-efficient than other light sources. If you compare a LED light to a halogen, you can see exactly how much more efficient.
- Halogen bulb = 90% of the electricity is used to generate heat, leaving 10% for light.
- LED light = 85% of electricity generates light.
Not to mention that a LED uses considerably less power.
LED lights also have a long life expectancy—50,000 hours on average. So if you could get your solar light to stay on 12 hours a day, the light should last 11 years. The LEDs in solar lights are rated for 10 years.
Finally, LED lights are durable. They are encased in plastic instead of glass and can handle harsh weather. It is rare for a LED to be the cause for a light to stop working.
The miniature version of solar panels on solar lights captures sunlight and converts it into electricity stored in a battery. Small systems like solar lights are also called Pico solar cells, solar arrays, or solar cells to differentiate these panels from larger ones.
Outdoor lights use monocrystalline solar arrays for some of the same reasons as LED lights—they are efficient, generate the most power per surface area, and are more durable than other panels.
The panels can be covered in epoxy, PET, or tempered glass, and the type of covering affects their lifespan.
- Epoxy resin. These typically have three layers. An epoxy resin surface, the solar cell, and a printed circuit board (PCB). Many inexpensive outdoor landscaping products (including solar lamps) use epoxy resin panels. Their lifespan is generally 2+ years.
- PET laminated panels. PET is a type of polyester film that lets 93% of light through and is more durable than epoxy panels. The solar cell is surrounded by EVA (ethylene vinyl acetate) to insulate the cell. The surface of the panels will have more texture or a glossier sheen than the cheaper epoxy panels. PET panels have a 3+ lifespan.
- Tempered glass laminated panels. High-end outdoor lights often use glass panels. Because they are more durable, tempered glass panels are ideal for use in harsh climates. Instead of a 2-3-year lifespan, laminated glass panels are rated to last 10-15 years.
As with many things, you get what you pay for. Although glass solar lights are more expensive, they last five times as long.
As you can see, your solar light’s life is affected by the type of panel it contains. A controller sends power from the solar cells into the battery. It also has a photoresistor that measures when it is dark and a small transistor that turns on the LED light.
The photoresistor in a solar light is a smaller version of one in a streetlight. A photoresistor changes from a high conductor of electricity when light hits it, allowing the energy from the solar cells to charge the battery. When the photoresistor does not sense light, it doesn’t send energy to the battery, and the battery becomes the power source for the LED light.
A controller has no moving parts and is rarely the source of failure in a solar light.
Most problems that occur with solar lights are due to batteries. The batteries that come with the light are typically cheap and have a low capacity and fewer charging and discharging cycles. But the good news is that batteries can be easily replaced.
The most common rechargeable batteries are NiCd (Nickel Cadmium) and NiMH (Nickel Metal Hydride).
When nickel-cadmium batteries first came out, they had several advantages over older rechargeable batteries.
- When they use energy, the rate of discharge remains constant, even as their juice becomes exhausted.
- The charging time is short, usually an hour or two, due to their low resistance.
- Typically, NiCd batteries can be recharged 400-500 times. Simple math says that these batteries will last about a year and a half.
Also, nickel-cadmium batteries have a memory effect, meaning the amount of energy they can hold lessens if they aren’t entirely discharged. Since most solar lights don’t make it through the entire night, this is not a significant problem.
Outdoor temperature is something we have little control over, and both hot and cold temperatures affect discharge rates of nickel-cadmium batteries. They also lose around 10% of their energy per month when stored. Some manufacturers suggest you bring in solar lights for the winter. If so, completely discharge them before you do.
These batteries have twice as much energy as the same sized nickel-cadmium. They also last longer than NiCd batteries and are less affected by temperature changes. This is good if you forget to bring your lights in when temperatures fall below freezing.
Another advantage of NiMH batteries is they do not have a memory effect. If you live in an area with frequent overcast skies, they might not have enough sunlight to charge fully, but this doesn’t affect them in the same way that it does batteries that suffer from the memory effect.
NiMH batteries are considered more environmentally friendly. Cadmium is a toxic chemical and should be disposed of at a local battery disposal site or drop-off point. Hydrogen is not regarded as toxic, so if battery recycling facilities are not available, you don’t have to feel guilty about throwing them in the trash.
The main disadvantage of these batteries is their cost, but the extra cost is worth it since they last longer and perform better. And if you forget which batteries to buy, remember that the NiMH ones will make you happier.
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The On/Off Switch Can Shorten the Lifetime of a Solar Light
One feature that can cause problems that is rarely discussed is the on-off switch. The purpose of this switch is to let the battery charge to full capacity before you turn on the light. However, these switches begin to corrode as moisture from the weather enters the housing. This corrosion causes problems with the function of the batteries.
A fix that sometimes works is moving the switch back and forth quickly to reestablish contact. Another is to take out the battery and look for corrosion. A product like DeOxit Cleaning Spray removes corrosion, but it is not cheap.
Since an on/off switch doesn’t make much sense with a solar light anyway, try to buy ones without them.
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How long a solar light lasts depends on the type of solar panels it has and the kind of battery you put in it. You can’t do much about the kind of panel, but you can change out the battery. Expect an inexpensive light to last anywhere from 2 to 4 years. If you want them to last longer, then shell out the extra money for lights with tempered glass solar panels.