Those who deal with the repair and maintenance of Electric Vehicles (EVs) need to be aware of the risks and safeguards associated with working on EVs and appropriately trained to deal with them — especially concerning fire safety regarding the lithium batteries that fuel them.
The risk of fire has always been an important element of health and safety (H&S) legislation when working on vehicles due to the flammable nature of the fuel in internal combustion engine-powered vehicles.
Those dealing with vehicle repair and maintenance, such as garages and service stations, are therefore required to take fire safety seriously as part of their H&S provision.
Hybrid vehicles, however, present a unique challenge when it comes to battery fires, and existing fire suppression systems and extinguishers may not be up to the task. As the number of hybrid and full electric vehicles continue to rise, it’s important to take a look at fire safety provision to ensure businesses are protected against lithium-ion battery fires.
What are the dangers?
While lithium-ion (Li-ion) batteries are generally very safe, especially battery packs designed specifically for the automotive sector, failures do occur.
It is when the Li-ion batteries are damaged, or simply suffer a component failure, that they can become dangerous. There have been increasing reports of instances of fires in EVs, and the charging units themselves, during recharging operations and battery recycling operations.
Main Causes of Fire
Li-ion battery fires can be quick and explosive, sending out dangerous projectiles, or slowly smoulder, or both. The resultant heat generated can be intense and the fumes highly toxic. Extinguished fires can also unexpectedly reignite.
Li-ion batteries should therefore be treated as hazardous materials.
The three main causes of lithium battery fires are thermal, mechanical damage and electrical overload — the latter being the more prevalent.
Of all the types of lithium batteries in use it is the Li-ion batteries used in EVs that present the most severe consequences of rechargeable battery failure if charging is not carried out using the correct charging technology or procedure. Li-ion batteries cannot tolerate overcharging and cannot be trickle charged continuously because of this.
Overcharging can result in the deposition of lithium metal on one of the electrodes, which then becomes a fire hazard. The battery must be charged using a charger that follows a rigid charging regime and has both overheat protection and time-out protection.
To prevent external damage or short circuit, electric vehicle batteries are usually surrounded by a protective cooling shroud filled with coolant liquid. In addition, in spite of external cooling, all electric vehicles are installed in an array rather than one huge lithium-ion battery pack to prevent damage from malfunction.
One of the main issues where Li-ion batteries do fail is the increase in temperature, known as thermal runaway. Thermal runaway is an unstoppable chain reaction causing a fire at temperatures of 60 and above.
Li-ion batteries are all susceptible to thermal runaway due to having larger battery packs with more cells to put in larger battery packs, with packed capacity. Containing a flammable liquid electrolyte in each cell in a Li-ion battery, when the cell short-circuits, the electrolyte can combust and the pressure will increase at speed.
Once the battery has been damaged, these heat generating processes will typically continue until all the energy the battery is storing has been dissipated. Some of the heat sources that could be present in a Li-ion battery fire include traditional combustion, ohmic, thermodynamic and chemical.
With the addition of the electrical energy, these ohmic and thermodynamic heat sources can cause very dangerous fires very hard to extinguish the fire with conventional extinguishers as. This due to the design of the batteries making it difficult to apply extinguishing agents to the source of the heat.
With conventional agents like water or foam, you may also need to continue dousing the battery until all its energy has dissipated. In the case of a large vehicle battery, this may take some time.
Thermal runaway can occur even when the battery is not plugged in; where batteries are older i.e. recharged more, the higher the potential risk of battery failure.
Solutions to Prevent Battery Failure
Manufacturers are designing several ways to prevent and reduce the impact of thermal runaway in electric cars.
The electrolyte in lithium-ion batteries, which is full of flammable materials with harmful chemicals, can catch fire under any circumstances. However, manufacturers are addressing the problem by dividing the battery into small cells with separating fire-walls. It can be at least delayed from spreading to neighbouring parts. Some engineers are making less risky electrolytes: less flammable and produce fewer harmful chemicals.
Thanks to the ongoing development and research, there have not been serious electric vehicle incidents yet. However, it should be still required that electric vehicles are sure to be safer than internal combustion engine vehicles in every regard.
Lithium Batteries and Workplace Safety
The fire safety procedures in any garage should be based on keeping all members of staff safe. Vehicle fires are extremely dangerous and should be tackled by professional firefighters. Make sure that staff are trained on being extremely cautious with vehicle fires, especially if the vehicle’s batteries are in a closed location where hydrogen and ethane has had the opportunity to build up. However, there is also a prevention element to help manage the risks.
Li-ion batteries should be regarded as hazardous materials and included in risk assessments as such. The safe handling of Li-ion batteries should include:
- Ensuring staff are made fully aware of the dangers of working with Li-ion batteries and are provided with appropriate training.
- Having safe practices in place regarding the supervision, detection and suppression of the hazards of Li-ion batteries.
- A suitable evacuation plan should a lithium battery fire occur.
- Inspection of batteries for signs of damage or possible failure (e.g. emitting a hissing sound).
- Storing batteries separately or away from combustible materials.
- Removing the batteries from the vehicle for long time storage at temperatures of between 5 and 20 degrees C.
- Avoiding any mechanical damage to the battery while working on the vehicle.
- Ensuring recharging is correctly carried out and preferably under supervision.
- Disposal of damaged cells and those that no longer hold a substantial charge by taking them to a dedicated collection/recycling facility, if possible.
Getting Appropriate Fire Extinguishers
Existing fire extinguishers on the premises may likely not be very effective at tackling Li-ion battery fires. Many in the motor trade are turning to a new form of fire extinguisher to help them manage the risks of hybrid vehicle fires. When reviewing fire safety procedures in light of the growth of hybrid and electric vehicles, it’s worth considering these new types of extinguishers.
The agent in these specialist extinguishers has been specifically formulated to stop the thermal runaway processes at work in these kinds of fires. The vermiculite particles within the agent forms a film over the top of the fire, preventing it from spreading and bringing the fire under control. Because electric vehicle batteries are made up of lots of smaller cells, this can be a very effective method for stopping a small fire spreading across the entire battery and becoming extremely dangerous.
This article is supported by our risk management partners, Health & Safety Click. For more information, please visit www.archriskmanagement.co.uk. Registration is free for existing Arch policyholders. If you require more information, please contact your local Arch branch manager.