Industry experts analyze causes of battery electric vehicle fires

Arc flash, electric shock, and thermal runaway from overheated battery top health and safety risks in Ontario mines

Tom Welton
Tom Welton, WSN Director of Prevention Services and Education Programs, writes down information from the mining industry advisory group during a root cause analysis of battery electric vehicle fires in underground mines.


Poster: Top causes of battery electric vehicle fires - Download, print and share

With the increasing use of battery electric vehicles in Ontario underground mines, new health and safety research has found that fire caused by thermal runaway, arc flash, and electric shock from overheated batteries are top health and safety risks with the newer technology.

Ontario mines began using new battery electric vehicle (BEV) technology around 2012, and ten years later, it has grown so popular most underground mines are moving toward this type of vehicle.

The benefits of using BEVs in underground mining is the decrease of diesel emissions, a known carcinogen, which improves worker health and safety by being emissions-free. BEVs are also much quieter and smoother to operate than traditional diesel machines. The technology helps mines save on fuel, ventilation, and cooling costs, as well as maintenance, since the vehicles have fewer moving parts.

Over the past decade there has been a learning curve on BEV health and safety that included incidents of fires and improper storage. At symposiums in 2020 and 2021, Ontario Mine Rescue reviewed its emergency responses to battery fires. Unlike car batteries, mobile equipment batteries are the size of a small chest freezer and can only be moved using lifting equipment.

Health and safety standards and legislation are catching up to the new technology, with the Canadian Standards Association (CSA) recently finalizing the CSA M424.4:22 Self-propelled, electrically driven, non-rail-bound mobile machines for use in non-gassy underground mines in August 2022. Access to this new standard will help create industry consistency in advancing BEV workplace safety.

“The CSA standard will help provide a consistent approach for industry,” says Tom Welton, Director of Prevention Services and Education Programs at Workplace Safety North (WSN). “Battery electric vehicles were brought in without foundational standards in place. Other industries are dealing with this, and people don’t have consistent guidelines.

"This standard will be a significant step ahead," notes Welton. "This research will definitely help industry and government ensure a strong foundation is built. Ongoing industry learning and research will continue to guide advancements and help build a strong foundation into the future.”

The research process

The risk assessment method harnesses the collective wisdom across the mining sector to focus industry, health and safety associations, and government, on the highest risks to health and safety.

The approach draws on industry, worker, management, health and safety association, and Ministry knowledge of risk and recognizes that a one-size approach does not fit all. The research draws on real-life insights into risk management and operations research, and decision science.

With three subject matter experts each from labour and management, the workshop process was open, transparent, and collaborative and ensured every viewpoint was heard. Each response was respected and not freely edited. The final list was shared with workshop participants before the workshop, and final workshop results were also reviewed and confirmed by industry participants.

The focus was on finding acceptable solutions that all members can support. Only industry experts ranked the risks, not government or health and safety associations. The process was not about consensus, although the results show a significant degree of convergence.

The risk assessment

Previously, with the support of the Mining Legislative Review Committee (MLRC) and the Ministry of Labour, Immigration, Training and Skills Development (MLITSD), Workplace Safety North planned and facilitated a risk assessment with the Ontario mining industry on battery electric vehicles.

Five of the top ten risks in the assessment research were related to fire: thermal runaway (fire), arc flash, and electric shock, so the industry group focused on the root cause of BEV fires.

The root cause analysis

In December 2021, with the support of the MLRC and the MLTSD, WSN planned and facilitated a root cause analysis of the risk of battery electric vehicle fires in Sudbury, and people attended either in-person or via Zoom.

“The mining industry is very excited to contribute to this research,” says Welton. “A number of the individuals in the group were also engaged in the development of the CSA standards as part of that group as well, so they were a really nice link.

“And we had actual operators and electricians and maintenance people on from a worker perspective. They were very encouraged to be part of this because they saw it as addressing a number of the gaps in relation to inconsistencies that were happening out there within industry.”

Identifying leading indicators

Using the risk assessment method and analyzing root causes within the workplace is an extremely effective method to understand and identify leading indicators that allow the industry to work more proactively in addressing key health and safety concerns.

“This research addressed foundational elements,” says Welton. “Things like issues with maintenance standards. Either you have a core standard that everyone’s working towards, or else everyone is developing their own. Same thing with BEV health and safety training. The absence of provincial standards leads to an inconsistent approach on how best to address these risks.”

Following review and discussion, both industry labour and management voted that the root causes of BEV fires had to do with inadequate guidelines around maintenance, training, policies and procedures, and ineffective management of the change due to newer technology. The root cause analysis risk statement was: “Thermal runaway event can result in unintended adverse effects on the wellbeing of workers.”

“The root cause of fire was the number one risk we focused in on, particularly arc flash and thermal runaway, which ties directly with fire,” says Welton. “Because of the voltage of those batteries, issues like arc flash and fire from thermal runaway are a very real concern.”

The following list shows the root causes of the battery electric vehicle fires, which were decided by workers, supervisors, and employers in the Ontario mining industry.

Top root causes of battery electric vehicle fires in Ontario mines

Arc flash, electric shock, and thermal runaway from overheated batteries are top risks*

1. Inadequate maintenance processes

2. Current lack of Canadian Standards Association standard for battery electric vehicles**

3. Ineffective management of change on new equipment†

4. Energy sources creating potential for electric shock

5. Ineffective company operator and maintenance procedures

6. Improper troubleshooting on issues with battery electric vehicle machines

7.  Operator lack of training on battery electric vehicles

8.  Lack of education and understanding on safety use of battery electric vehicles

9.  Misuse of new battery electric vehicle equipment (no maintenance records or standards)

10.  Rushed implementation of battery electric vehicle use

11. Lack of common core training standards for battery electric vehicle use

12. Improper or unclear work delineation for electricians and maintenance personnel

13. Inadequate battery storage

*In batteries, thermal runaway describes a chain reaction in which the battery releases energy in the form of heat, once started can be very difficult to stop. Thermal runaway begins when heat generated within a battery exceeds the amount of heat dissipated to its surroundings. When thermal runaway occurs, temperature rapidly increases, resulting in uncontrolled heat with potential of fire.

**Canadian Standard Association mining standard released summer 2022: CSA M424.4

Effective ‘Management of Change’ involves the review of significant organizational changes to ensure an acceptable level of safety is maintained after a change has been implemented.

Results show need for new processes and procedures

“It was a very open discussion,” says Welton. “Everyone was along the same lines, be it the labour or the management side, as far as showing some weaknesses because battery electric vehicles had been brought on-stream so quickly that the management of change process could’ve been addressed better from their perspective, which created issues with training, it created issues with no legislated standards. The root cause analysis by industry has been helpful in finding where new processes and procedures and policies need to be developed and put in place.

“From a legislative point of view, the Ministry is quite interested in these results as well as upgrading their legislation to incorporate battery electric vehicles. The research is very helpful in directing legislation and key weaknesses that need to be addressed by the law,” says Welton.

“The health and safety training requirements will also tie in the CSA standards from a frontline worker perspective, focusing on the important things workers need to know in relation to battery electric vehicles,” adds Welton.

Next steps

On Nov. 9, a free online seminar, "Mining Safety: New Research on Root Causes of Battery Electric Vehicle Fires," will be co-hosted by WSN and the Ministry, to discuss the results of the research.

In 2023, Workplace Safety North will host a symposium on battery electric vehicle safety and discuss the results of the research.

“We’ll get a chance to update the industry on the next steps from this risk assessment-root cause analysis process,” says Welton. “With every one of our risk assessment-root cause analysis there’s always been the next step: be it developing a training program, resource material, or doing a presentation at the upcoming symposium.

“We’ll explore going further. We’re working with industry and the MLRC and the mining tripartite committee really pushing ahead those core elements: the CSA standard is key to moving forward.”

The risk assessment and root cause analysis regarding battery electric vehicle safety is part of a larger research program that looks at top mining health and risks in Ontario mines, and the root cause of each one. To date, top risks and root causes have been identified for ground instability, mobile equipment, and water management.

For more information, contact Workplace Safety North.


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Mining poster - Top Root Causes of Battery Electric Vehicle Fires

Battery Electric Vehicles Risk Assessment Workshop Results

Battery Electric Vehicles Root Cause Analysis Workshop

Recommended Practices for Battery Electric Vehicles in Underground Mining - Global Mining Guidelines Group

Battery Electric Vehicles – free workplace safety resources

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Free mining health and safety resources