Fellow engineers we are looking for your assistance in trying to highlight the issues surrounding Lithium-Ion batteries in particular battery fires. Due to the lack of data available and the fact that the National Statistic Office is not currently collecting the data required, we do not fully understand the extent of the problem. However, we do know that there has been many electric vehicle car fire either whilst in use or whilst charging. Additionally, Zurich Insurance highlight that ‘Fires sparked by e-bikes and e-scooters have surged 149%, triggering a warning over the dangers of “exploding” lithium batteries ahead of Christmas’.
I would be appreciative if you would spare the time and read the information below and provide constructive comment, you may have experienced a lithium-ion fire or you may work in the industry. Our fire fighters are trying to identify the best way to extinguish these fires and prevent re-ignition . However, we need to identify the root cause of these fires. Our aim is to catch the interest and influence future government policy: one death is one death too many.
I look forward to your comments, the information below is just thoughts to help define a policy document that saves lives.
Global air temperatures near the Earth’s surface have risen by about 2 degrees Fahrenheit in the last century. In fact, the past 5-years have been the warmest. Therefore, in a bid to reduce CO2 emissions, with the effect from 2035, fossil fuel cars will no longer be produced.
As a country we need to reduce CO2 emissions and the reliance on fossil fuel must be reduced by the means of an alternative fuel, whether that be hydrogen power or battery power. Currently Lithium-ion batteries are the common power source in EV; however, there could be a safety concern associated with this type of battery and that is thermal runaway. Lithium-ion batteries are self-oxidising; therefore, when on fire, they can produce their own oxygen and fire investigators are identifying methods to extinguish the fire and prevent reignition. But should we not be investigating the root cause of the fire and thus reduce the chance for a fire to occur.
The aim of this paper is to question why do lithium-ion battery fires occur in EV and how we can reduce the occurrences.
Key Notes and Thoughts.
By 2050 it is expected that there will be up to 50 million electric vehicles on our roads.
Since 2017 to 2022 there had been over 735 fire brigade callouts across the UK for lithium-ion battery fires. However, as a comparison, there has been on average 300 fires involving fossil fuelled vehicles a day in the UK. But 65% of these vehicle fires would be crime related.
The data with regards to Home Office Fire Statistic involving EV and Lithium-ion battery fires is in the early stages of development. Therefore, the data is limited.
Possible lack of publicity with regards to Lithium-ion battery fires.
Battery Thermal Runaway is one of the reasons for lithium battery fires; but are the battery manufacturers acquiring the data to analysis the failure modes to prevent such occurrences?
Has the UK government stipulated any additional regulations and standards for the sale of EV and its associated battery in the UK?
Should an internal alarm be fitted to EV in the event of a gas leak or fire?
EV ‘Powered by highly flammable batteries and packing high voltage electrical systems, it's easy to see how EV could give cause for concern. In reality, though, electric cars are just as safe as any other, thanks to a range of neat features aimed at protecting occupants and other road users[i]’.
There is approximately one million electric and hybrid vehicles on the UK roads and it is estimated that by 2050 there will be up to 50 million electric vehicles on our roads. Although evidence of EV fires is relatively low, the impact from such a fire occurring is catastrophic and the loss of one life, is one life to many. Therefore, should one say that EV are inherently safe?
Incidents Involving EV.
Most people assume the term EV is for an electric car. However, the term EV is more global as it encompasses: cars, bikes, scooters, lorries and buses; and this could cause an issue during the recording of data with regards to lithium battery fires. The vehicle types need to be broken out to help understand the risk to life.
The last five years has seen a dramatic increase in fires caused by electric vehicle batteries in the UK, with a sharp rise in incidents taking place last year, unique data gained by CE Safety has revealed:
The growth in popularity of electric vehicles has led to cars, scooters, bikes and motorbikes setting alight, with a total of 735 callouts across 29 fire and rescue services across Britain since 2017.
However, the recording of EV fires is still in its infancy as demonstrated in the Home Office, detailed analysis of fires attended by FRSs, England, April 2020 to March 2021: data tables. The data does not appear to contain analysis specific to EV Fires involving lithium batteries and/or break it down into vehicle types.
Battery Vehicle Car/Bus/HGV In Use; Not in Use; Whilst Charging; Accident.
Battery Scooter In Use; Not in Use; Whilst Charging; Accident.
Battery Bike In Use; Not in Use; Whilst Charging; Accident.
However, AutoinsuranceEZ[ii], an American insurance company investigated the rate of car fires by vehicle type. They collected the latest data on car fires from the National Transportation Safety Board and calculated the rate of fires from sales data from the Bureau of Transportation Statistics. There data revealed that per 100,00 car sales there were:
3,474 Hybrid Vehicles fires.
1,529 Fossil Fuel Vehicles fires.
25 EV fires.
Furthermore, there is evidence of EV fires occurring during the transportation of the vehicle:
BBC News - 5 December 22. A section of the M1 was closed in both directions as firefighters tackled a car transporter blaze. Both carriageways were shut at about 13:40 GMT after a fire broke out on the southbound carriageway near Nottingham, between junctions 26 and 27. Nottinghamshire Fire and Rescue Service said seven electric vehicles on the transporter were left "well alight".
What caused this fire to occur? Was it an EV that spontaneously combusted and caused the fire or was the transporter overloaded. On average EV’s weigh 30% heavier than their equivalent fossil fuel vehicle. Could this increase in weight put stress on the transporter’s braking or suspension system and cause a fire?
Fleetmom – 3 February 23. Although the cause of fire is undetermined, a container ship the Ah Shinwas reported to be on fire in South China Sea. The ship was carrying 4530 cars. On the 7 Feb, it was reported that there was no open fire, but crew and firefighters believe there still might be smouldering spots, specifically electric batteries.
In a bid to be impartial every year in the UK, over 100,000 fossil fuel vehicles, which equates to nearly 300 a day, go up in flames and around 100 people die as a result. However, around 65% of these fires are started deliberately to cover criminal activity, to make a fraudulent insurance claim or as an act of vandalism[iii].
E-Scooters and E-Bikes. Out of interest, the London Fire Brigade attended over 70 fires involving e-scooters and e-bikes in 2021. Their website: https://www.london-fire.gov.uk/safety/the-home/e-scooters-and-e-bikes/ provides sound advice to owners of E-Scooter and E-bikes, but why is it not more widely available in the national press?
A lithium-ion battery pack consists of lithium-ion cells stacked together in modules, temperature sensors, voltage tap and a Battery Management System to manage the individual cells. Like any other cell, the lithium-ion cell has a positive electrode (cathode), a negative electrode (anode) and a chemical called an electrolyte in between them. While the anode is generally made from graphite (carbon), different lithium materials are used for the cathode:
Lithium Cobalt Oxide (LCO). Popular choice of battery for laptops, cameras and mobile phones.
Lithium Nickel Manganese Cobalt (NMC). Preferred battery for EV; however, high charge can promote thermal runaway.
Lithium Manganese Oxide (LMO). A good all-round battery, but its performance and lifespan is below average. Used on power tools, medical devices and electric powertrains.
Lithium Iron Phosphate (LFP). Commonly used for power storage. One of the safest batteries. A good replacement for the lead acid battery.
When a charging current is provided to the cell, lithium ions move from the cathode to the anode through the electrolyte. Electrons also flow but take the longer path outside the circuit. The opposite movement takes place during discharge with the result that the electrons power up the application that the cell has been connected to. When all the ions have moved back to the cathode, the cell has been completely discharged and will need charging.
Battery manufacturers may use a mix lithium material to obtain the best performance and safety. However, even though lithium batteries are, the majority of the time, produced with built in protectors; thermal runaway and fires still start. The question is why?
‘Battery packs store large amounts of energy in a very small space, which is why they can get hot[iv]’. Excessive heat causes a chemical reaction, which in turn cause more heat; this escalating cycle is known as a thermal runaway. But what can initiate a thermal runaway?
An internal failure of a battery component.
An accident, where the battery has been crushed/punctured, causing a short circuit.
Excessive charging and discharging of the battery.
Driving the vehicle hard using much of its power, then rapidly charging the battery and there is a system failure.
Failure of the battery cooling system.
The use of unofficial chargers.
Some of the above-mentioned failures could be prevented as data on failure modes should be available for analysis and by using reliability centred maintenance, replacing components in a timely manner should assist in preventing a catastrophic failure of the system.
Notwithstanding the issues mentioned above, the latest generation of EVs have been thoroughly tested for all safety measures. EV battery manufacturers have been addressing the challenges of short circuits and thermal runaway through rigorous testing.
Additionally, manufacturers have also been working on intelligent Battery Management Systems to perform the tasks such as: monitoring cell voltage and temperature and providing thermal and overcharge protection, which isolates the battery pack from the load when necessary and monitors battery health.
Battery Fire Re-ignition.
The positively charged electrode (cathode) in the battery contains oxygen. Therefore, when a lithium-ion batteries burns, the cathode material breaks down and releases O2, and as a consequence of the battery’s combustion, it will also release; hydrogen, methane, carbon monoxide and hydrofluoric acid. The make-up of EV batteries makes it easier for battery fires to reignite as the fire can spread from one cell to the next. Hence why it is difficult to extinguish the fire due to the capability of the battery to self-generate oxygen.
Battery Design Breakthrough?
A battery design breakthrough could make electric cars safer, cheaper and more environmentally sustainable[v]. The Zinc-ion design addresses safety issues by being non-flammable, not containing toxic organic electrolytes and ‘aid the transition to a sustainable future’.
Researchers from Tianjin University in China discovered a way to improve the performance and cost of aqueous zinc-ion batteries, which until now have been prone to fast performance degradation. The high performance and reusability of lithium-ion batteries mean they are the standard power source for most rechargeable electronics; however, issues with cost, safety and sustainability have led scientists to seek breakthroughs with alternative materials.
In the meantime, although lithium-ion battery manufacturers are using Research and Development to get the most out of their battery packs, which includes thermal management, battery life and safety. I must ask are their investigations concentrating on looking at causal factors of fire and how to prevent fire occurring or their profit margin?
Injuries and Regulation.
The injury hazards in a crash could be categorised into six groups: impact injury, electric shock, corrosion, intoxication and burns. However, there are international standards for crash regulations that must be satisfied in order to be approved for sale and individual countries can enhance those regulations to meet their countries safety requirement. However, errors/accidents will still occur, but is the UK Government doing enough to protect people from EV fires, or are they solely concentrating on green issues associated with EV?
One question to be discussed; should EVs have an alarm fitted to the vehicle to inform either:
The occupants in the vehicle of the battery venting excessive gas.
To inform people in the vicinity of the vehicle that a fire has occurred.
Thus, allowing them to either safely egress the vehicle and/or vacate the area.
What to do if your EV is on fire[vi]?
London Fire Brigade’s Assistant Commissioner for Fire Safety, Charlie Pugsley, was asked for some guidance on what to do in such an emergency. He inferred: “If an electric or hybrid vehicle catches fire or starts to produce plumes of white smoke, our advice is to safely stop the vehicle and get out immediately. “The white smoke produced by these fires is highly toxic and must never be mistaken for steam. Make sure you and anyone else move a safe distance away from the vehicle, do not attempt to retrieve items from inside or tackle the fire yourself, and call the fire brigade.”
EV Charging Facilities.
Having just looked around a recently built EV Charging facility, comprising of several Fast rated charges and one Rapid Charger. I noted that there was no facility to call the emergency services. Yes, most people carry mobile phones, but what if you left it in the car. More importantly, this charging facility backed onto a petrol station. On the opposite side of a wooden fence from the charging bays was the gas bottle compound and then the fuel pumps. Although, there are regulations: ‘Hazardous Area Classification and Control of Ignition Sources’ for Explosive Atmospheres. One could interpret the factors for the safety case as ALARP with regards to EV fire, due to the lack of evidence for EV fires in the UK, when the vehicle is charging. The regulations have been interpreted for the chargers themselves; providing safety distance from places that release inflammable fumes intermittently. Therefore, a charger, which is not a flameproof device/intrinsically safe, cannot be mounted close to a petrol pump. But it is not the charger that is the issue, it is the car. Low frequency, high impact springs to mind.
[iii] https://www.fireservice.co.uk/safety/vehicle-fires/ 23 May 2018.
[iv] Professor Paul Christensen, AirQualityNews.com.
[v] Anthony Cuthbertson Thursday 2 December 2021 | 16:01 The Independent