A number of organisations have reported incidents with the lithium-ion batteries on power tools catching fire or exploding. Please follow link to watch the video that provides a chilling example of the type of fires that can occur.
The use of battery powered tools is increasing, both in numbers being used and the size of tool for example disc cutters/floor saws with voltages increasing to up to 50 volts. The quality of packaging protecting the tools is becoming cheaper whilst the tools may be exposed to damage from rough handling such as being thrown around in the back of vans. This can increase the risk of the type of incident shown on the video increasing.
In addition to the fire risk, if the gasses produced from a fire were inhaled this could result in serious consequences with a potential risk to life!
An individual, who has spent some time in the recycling sector, has personally been involved in two major fires where people have attempted to recycle cells incorrectly.
Common ways in which damage to a battery can occur
Lithium-ion battery failures can occur due to imperfections in the construction of the cell or through abuse. Damage to cells, packs or modules can create the risk of fire. The damage could arise from incidents such as a simple impact, dropping or collisions in transit, piercing from tooling, shorting, over charging, being exposed to higher or lower temperatures than those the battery is designed for. Interestingly, once a battery has been damaged, fire or explosion is not instantaneous, it may take some time to develop symptoms such as swelling or heating.
Possible reactions once damaged
Lithium-ion batteries can react in a variety of different ways depending on the type of fault, the area that is damaged, state of charge and chemistry of the affected battery. It has been difficult to consistently predict the same failure behaviour of a cell, even in laboratory conditions.
• Damaged cells may vent / smoke without ignition.
• Fires may occur when the electrolyte ignites.
• A jet of flame and burning material being ejected from a single point can create a flare.
• The battery may burn or create a fireball, depending on the failure mode.
• The battery may also explode.
Lithium-ion cells can transition between reactions. Venting cells can catch fire, then explode, they may also vent then explode without catching fire.
Burning lithium-ion cells can and do create carbon dioxide and water. This smoke is generally made of hydrogen, carbon monoxide, carbon dioxide and a range of hydrocarbons although the exact composition of the smoke is dependent on the chemistry used. Fluorine can also be released from the battery, which can combine with hydrogen to produce hydrogen fluoride, this in turn will react with water, including water vapor or with mucus membranes in the human body to create hydrofluoric acid, nasty stuff!! Fumes of Fluorine inhaled at and once absorbed into blood reacts with blood calcium and may cause cardiac arrest, worthy of note for vulnerable people with conditions being at increased risk!!
Once a battery cell has failed the heat generated can cause other cells in close proximity (stored together or together in modules and packs) to fail, resulting in a chain reaction (also known as the snowball effect or runaway).