|The safety of lithium-based batteries has attracted much media and legal attention. Any energy storage device carries a risk, as demonstrated in the 1800s when steam engines exploded and people got hurt. Carrying highly flammable gasoline in cars was a hot topic in the early 1900s. All batteries carry a safety risk, and battery makers are obligated to meet safety requirements; less reputable firms are knowns to take shortcuts and it’s “buyer beware!”
Lithium-ion is safe but with millions of consumers using batteries, failures are bound to happen. In 2006, a one-in-200,000 breakdown triggered a recall of almost six million lithium-ion packs. Sony, the maker of the lithium-ion cells in question, points out that on rare occasions microscopic metal particles may come into contact with other parts of the battery cell, leading to a short circuit within the cell.
Li-ion batteries – a fire hazard
Physical damage to battery cells, pollution in the electrolyte or the poor quality of the separator may cause a fire in li-ion batteries.
An explosive fire in a Lithium-Ion battery
In June 2018, a client of ours experienced an explosive fire in a Lithium-Ion battery used for a custom-built electric bike. The owner of the bike was about to show the battery to his family when it suddenly caught fire lying on the kitchen table! The battery was connected, neither to the charger nor to the bike.
The fierce fire, experienced by our client as being like fireworks, could not be extinguished, and the fire spread to the interior and the building structure, causing a near-total loss of the building.
Our own investigators have done technical studies of the damaged battery and the battery cells. The probable root cause of the fire is physical damage to the battery, causing thermal runaway in the battery. The built-up pressure was released through cracks in the first battery cell affected, causing thermal runaway in some of the other cells.
The root cause of the fire
Senior researcher Helge Weydal, at the Norwegian Defence Research Establishment (FFI), explained the hazards of Li-Ion batteries in an article in Risk Consulting issue 2/2017. Fires can be caused by physical damage to battery cells, such as that which our client experienced, or they might also be caused by pollution in the electrolyte or the poor quality of the separator.
Countless numbers of devices
The number of devices using Li-Ion batteries in households and businesses worldwide is enormous. We are surrounded by billions of devices: mobile phones, laptops, radios, cameras, flashlights, radios. Equipment that consumes even more energy, such as lawnmowers, other power tools, and in the Nordic countries even rotary snowploughs, belong to households.
Electric cars are coming rapidly into several international markets. Buses, ships, ferries, large trucks, and even aeroplanes are being developed for commercial purposes, all using Li-Ion technology as the power source. Large Li-Ion battery banks are used in power storage for optimising solar power technology.
What to Do When a Battery Overheats or Catches Fire
If a Li-ion battery overheats, hisses or bulges, immediately move the device away from flammable materials and place it on a non-combustible surface. If at all possible, remove the battery and put it outdoors to burn out. Simply disconnecting the battery from charge may not stop its destructive path.
A small Li-ion fire can be handled like any other combustible fire. For best results use a foam extinguisher, CO2, ABC dry chemical, powdered graphite, copper powder or soda (sodium carbonate). If the fire occurs in an airplane cabin, the FAA instructs flight attendants to use water or soda pop. Water-based products are most readily available and are appropriate since Li-ion contains very little lithium metal that reacts with water. Water also cools the adjacent area and prevents the fire from spreading. Research laboratories and factories also use water to extinguish Li-ion battery fires.
The crew can’t access the cargo areas of a passenger aircraft during flight. To assure safety in case of a fire, planes rely on fire suppression systems. Halon is a common fire suppressant, but this agent may not be sufficient to extinguish a Li-ion fire in the cargo bay. FAA tests found that the anti-fire halon gas installed in airline cargo areas can’t extinguish a battery fire that combines with other highly flammable material, such as the gas in an aerosol can or cosmetics commonly carried by travelers. However, the system prevents the blaze from spreading to adjacent flammable material such as cardboard or clothing.
With the increased use of Li-ion batteries, improved methods to extinguish lithium fires have been developed. The Aqueous Vermiculite Dispersion (AVD) fire extinguishing agent disperses chemically exfoliated vermiculite in the form of a mist that provides advantages over existing products. AVD fire extinguishers are available in a 400ml aerosol can for a small fire; AVD canister for warehouses and factories; a 50 liter AVD trolley system for larger fires, and a modular system that can be carried on a pickup truck.
A large Li-ion fire, such as in an EV, may need to burn out. Water with copper material can be used, but this may not be available and is costly for fire halls. Increasingly, experts advise using water even with large Li-ion fires. Water lowers combustion temperature but is not recommended for battery fires containing lithium-metal.
When encountering a fire with a lithium-metal battery, only use a Class D fire extinguisher. Lithium-metal contains plenty of lithium that reacts with water and makes the fire worse. As the number of EVs grows, so must the methods to extinguish such fires.
Simple Guidelines for Using Lithium-ion Batteries
A failing Li-ion begins to hiss, bulge and leak electrolyte.
The electrolyte consists of lithium salt in an organic solvent (lithium hexafluorophosphate) and is highly flammable. The burning electrolyte can ignite combustible material in close proximity.
Dowse Li-ion fire with water or use a regular fire extinguisher. Only use a Class D fire extinguisher for lithium-metal fires because of the reaction of water with lithium. (Li-ion contains little lithium metal reacting with water.)
If a Class Dextinguisher is not available, douse a lithium-metal fire with water to prevent the fire from spreading.
For best results dowsing a Li-ion fire, use a foam extinguisher, CO2, ABC dry chemical, powdered graphite, copper powder or soda (sodium carbonate) as you would extinguish other combustible fires. Reserve the Class
Dextinguishers for lithium-metal fires only.
If the fire of a burning lithium-ion battery cannot be extinguished, allow the pack to burn in a controlled and safe way.
Be aware of cell propagation as each cell might be consumed on its own time table when hot. Place a seemingly burned-out pack outside for a time.
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