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I’ve been thinking about fitting a couple of solar powered security lights to our property but when deciding where to fit my new lights it suddenly dawned on me that these lights contain batteries which could pose a fire risk.
Read on to see how solar lights work and what risks really exist.
Can solar powered lights catch fire? Solar powered lights are fitted with one or more batteries which are charged by a photovoltaic panel during daylight hours ready to power the light once the light fades. Any device which is fitted with and charges a battery has some potential to be a fire risk.
How do solar powered lights store power?
Inside each solar powered light is one or more batteries. The solar array which is usually either fitted directly to the top of the light or a separate unit attached via a length of cable charges the battery during daylight hours ready to power the light once the light fades.
The solar array converts the light into electrical energy which is passed to a controller which in turn charges the battery. The controller incorporates some safety circuitry which prevents over heating, over voltage, under voltage and over charging.
Battery types: good, better, best?
Modern solar powered lights are fitted with one of three different battery types namely Li-Ion (Lithium Ion), NiMH (Nickel Metal Hydride) and in rare cases NiCd (Nickel Cadmium). Each battery type has its pros and cons.
NiCd or Nickel Cadmium is the oldest and cheapest battery technology. These batteries are able to operate in extreme conditions of cold and heat (+30°C to +50°C), however they are susceptible to the memory effect which means that over time the battery does not utilise the full capacity of its cells.
Whilst this limitation can be overcome by proper charging and reconditioning practices, this is not really practical solution for solar lights.
NiMH or Nickel Metal Hydride offers a longer operation time between charges of up to 40% over that of NiCd but do not operate as efficiently in extreme temperatures.
Whilst NiMH batteries are not as susceptible to the memory effect as NiCd batteries, the effect is still present which means that over time the battery run time shortens.
Li-Ion or Lithium Ion has the ability to pack a lot of power into a very small package hence why Li-Ion is the preferred battery choice for many mobile devices such as mobile phones and laptops. They do not suffer any memory effect but are more volatile due to the chemistry and manufacturing methods.
Whilst NiMH batteries have been the preferred battery technology for solar powered lights for a number of years, Li-Ion batteries are becoming more popular as costs come down. Unfortunately it’s here that a higher risk of fire is introduced due to the volatility of Li-Ion cells.
What makes Lithium Ion Batteries so volatile?
Lithium is the least dense metal which means that it’s able to pack a lot of power into a very small space. As Lithium is also highly reactive this makes it combustible. On top of this, each cell sits in a highly flammable solution of lithium salts and organic solvents which can combust when exposed to heat.
Inside, the battery utilises a very thin, porous slip of polypropylene to separate the electrodes. If this separator is breached the electrodes come into contact with each other causing a short circuit which in turn causes a build up of heat known as a thermal runaway. You can see where we’re going here can’t you?
Lithium Ion batteries require the use of smart controllers to monitor the batteries condition and ensure that the battery can not be over charged or allowed to drain beyond a certain voltage. These controllers also monitor temperatures so as to shut down power to the battery in event that a fault is detected.
Whilst most reputable manufacturers will have many checks and balances to ensure the quality of their Lithium Ion batteries and controllers to reduce the risk of fire, it would appear that even the most reputable companies are not immune to the risks that Lithium Ion batteries pose.
Companies such as Apple, Sony, Hewlett Packard, Toshiba, Lenovo and Samsung have all had issues with Lithium Ion batteries exploding or spontaneously combusting during normal day to day use.
All-Pro and Defiant solar powered lights have recently come under fire for having defective lights causing the batteries to overheat and melt the fixture. With many of these lights having been attached to fences or directly to the house, the excess heat could easily start a fire.
The following All-Pro and Defiant models have been recalled.
- All-Pro MST800L
- All-Pro MST800LW
- All-Pro WPS2040M
- Defiant MST1000LWDF
- Defiant MST1000LWDFC
Buying Cheap Increases the Risk of Fire
In todays world of online shopping and the customers need to always plump for the cheapest option, there is a constant race between manufacturers and retailers to be the cheapest on the market in order to compete.
It’s little wonder that shortcuts are taken during the manufacturing process. Cheaper photovoltaic cells are sourced, cheaper Chinese cells are used in the manufacturer of the batteries and shortcuts are taken when it comes to the smart controllers that help prevent the batteries from bursting into flames.
Solar powered lights can be extremely reliable, with some even charging in cloudy weather but you simply can not expect this sort of quality without spending a bit more money.
We’ve come across many solar powered garden lights on sites like Amazon and eBay for less than $20 for a set of 12 lights. That’s $1.66 per light. $1.66 for the light housing including stand/spike and globe, photovoltaic panel, LED bulb, a battery and controller and in many cases free delivery.
Reducing the Risk of Fire
While it is apparent that even the most reputable companies are having troubles with keeping Lithium Ion batteries in check here are a few things you can do to reduce the risk of fire from your solar powered lights.
- Buy your solar powered lights from a reputable retailer.
- Whilst Amazon’s customer service is fantastic, do not always believe the reviews found on many products. It has been proven time and time again that reviews are more often than not fake.
- Don’t automatically opt for the cheapest option. Lithium Ion batteries and photovoltaic cells are still relatively expensive so you can not expect a cheap product to contain good quality components. While you may pay a little more for a decent set of solar powered lights, they should last you a lot longer than a cheap set and will probably perform far better too.
- Think about where you are going to place / mount your lights. If a light does catch fire in the middle of the garden the most that you will loose will be the light itself but a burning light attached to a wooden fence could cause a lot more damage to your property and possibly people.
If one of my lights catches fire, whats the best way to extinguish it?
For best results use a foam extinguisher. CO2, ABC dry chemical, powdered graphite, copper powder or soda (sodium carbonate). Halon is also used as a fire suppressant.
Of course if you don’t have one of these extinguishers to hand then use water or soda pop. Water also cools the adjacent areas and prevents the fire from spreading.
Li-Ion is highly reactive so once the fire has been extinguished, it’s advisable to leave the light outside for six hours before disposing of it.
Yes, Solar powered lights are at risk of catching fire. More so the ones fitted with Lithium ion batteries. The risk is however relatively low and can be mitigated by following a few simple precautions when choosing your lights and the location of installation.
Can LED lights catch fire? LED Lights on their own are highly unlikely to cause a fire. However depending on their power source the risk of fire may increase from the power source itself. ie. A cheap AC/DC Adapter or Battery.