Electric bus Li-ion battery fire protection solutions

FirePro presents exclusively for Fire Buyer magazine the latest in fire protection solutions to tackle electric bus Li-ion battery fires 

Cities are increasingly turning to electric buses as a way to reduce their carbon footprint and improve air quality. Compared to traditional diesel fuelled buses, electric buses are more energy-efficient, produce no emissions at the point of use, and have lower operating costs over their lifetime. Typically, these buses use Lithium-ion (Li-ion) batteries, which offer several advantages such as high energy density and fast charging. However, like with any technology, there are also risks associated with their use. 

In recent years, there have been several high-profile incidents involving Li-ion battery fires in electric buses. This has highlighted the need for improved safety measures and risk management strategies. In particular, the risk of thermal runaway, a chain reaction that can occur when a single Li-ion battery cell is subjected to mechanical, electrical, or thermal abuse, is especially high in electric buses. This is because a large number of Li-ion batteries are used in a relatively small enclosure. The excessive vibrations from normal bus operation can be a stress factor for Li-ion batteries, contributing to a potential short-circuit, overheating, and the release of gases that can lead to a fire or explosion. 

During a thermal runaway event, the Li-ion battery’s electrolyte starts to decompose (120oC), releasing a large volume of gases, which due to pressure build-up, ruptures the metal or plastic pouch casing containing the electrolyte. These gases normally burn (flash fire) at temperatures in excess of 800oC when in contact with the atmosphere (O2) producing a toxic, flammable or explosive mixture depending on the type of electrolyte used in the cell. Some examples of these gasses are hydrogen (H₂), carbon monoxide (CO), hydrogen fluoride (HF), hydrochloric acid (HCI), hydrogen cyanide (HCN), sulfur dioxide (SO2) and hydrogen sulfide (H2S). Furthermore, the excessive loss of lithium ions from the cathode material leads to a structural collapse of the cathode electrode, causing the release of oxygen (O2).   

How FirePro suppresses Li-Ion battery fires 

FirePro Condensed Aerosol technology suppresses fire by interrupting the chemical chain reactions that occur in the flame, rather than by cooling or depleting oxygen in the enclosure. Upon activation, the condensed aerosol forming compound transforms from a solid state into a rapidly expanding two-phase fire suppression agent; consisting of potassium carbonate solid particles K2CO3 (the active part) suspended in a carrier gas. When the condensed aerosol reaches and reacts with the flame, the potassium radicals (K*) are formed mainly from the dissociation of K2CO3. The K*s bind to other flame free radicals (hydroxyls OH-) forming stable products such as KOH. KOH then further reacts in the presence of CO2 and forms stable K2CO3. 

In the event of a Li-ion battery fire, both the active agent K2CO3 and the intermediate product KOH react with the electrolyte’s decomposition products, such as hydrogen fluoride (HF), forming stable products such as potassium fluoride (KF) and potassium bifluoride (KHF2). Thus, preventing the formation of highly flammable gases such as hydrogen (H2). The resulting neutralizing action ultimately controls the fire and allows the temperature in the enclosure to drop below the threshold necessary (120oC) for thermal runaway to sustain itself. Test results have shown that FirePro can protect the enclosure against re-ignition for as long as the minimum required fire suppression density is maintained, allowing ample time for passengers to evacuate the bus and for emergency responders to begin post-fire management of the batteries.   

Main challenges of Li-ion battery fires 

Heat output – In the scenario where the Li-ion batteries have entered an advanced thermal propagation stage, the battery generates its own heat, making it difficult to cool down.   

Oxygen supply – The production of oxygen during cathode and electrolyte decomposition supports the chemical processes that occur during a fire.  

Battery pack – Li-ion battery cells are densely stored in their packs making it hard for a fire suppression agent to reach the fire.  

FirePro solutions 

FirePro cylindrical models are compact and provide a practical solution for applications with space limitations such as the electric bus battery compartments. They can be installed directly within the battery pack or within the battery compartment which houses the battery packs.   

Each generator is an all-in-one system unit and is the equivalent of the agent storage tank, piping and nozzles of a pressurized gas system. They are activated automatically, either through electrical or mechanical means. A comprehensive fire-suppression system can be configured to include single or multiple generators, depending on the physical and technical parameters of the protected area, such as the class of fire, volume and height. In the case of a Li-ion battery hazard, the agent density used is the one proven to be effective in tests replicating real-life scenarios.  

A wide range of control and monitoring equipment can be used to automatically activate the generators, selected based on the project’s requirements. Some of the main considerations when choosing a control module include the type of detection technology used (e.g. thermal sensors) and the level of integration with other systems (e.g. vehicle control, alarm systems). Early detection, shutdown of the battery, and fire suppression is critical during a thermal runaway event to prevent its spread to neighboring cells.  The selection of the right control module and detection technology are part of the engineering of the system and are fundamental in meeting the expectations of the project’s fire strategy.  

To read more news and exclusive features see our latest issue here.

Never miss a story… Follow us on:
LinkedIn International Fire Buyer
Twitter logo @Firebuyer
Facebook Fire Buyer

Media Contact
Louis Curtis
Editor, International Fire Buyer
Tel: +44 (0) 1622 823 922
Email: [email protected]

About Fire Buyer

International Fire Buyer is the leading authority in global passive and active fire content, delivering expert news, in-depth articles, exclusive interviews, and industry insights across print, digital, and event platforms. Published 10 times a year, the magazine is a trusted resource for professionals seeking updates and analysis on the latest developments in the fire sector.

To submit an article, or for sponsorship opportunities, please contact our team below.

Chris Lingham image - Fire Buyer

Chris Lingham

Group Sales Manager

Afua Akoto picture - Fire Buyer

Afua Akoto

Marketing Manager

Read the Latest Issue

Follow us on X

Follow us on X

Click Here

Follow us on LinkedIn

Follow us on LinkedIn

Click Here

Advertise here

Reach decision makers and amplify your marketing

Advertise here

Click Here

Related News

Product Spotlight – FFE

Early, reliable fire detection is critical to protecting people, assets, and infrastructure in demanding settings – an evolving challenge

From the Expert – Stat-X

Ultrasense from Fireaway, a new generation of fire protection combines early anomaly detection and advanced aerosol suppression to

Feature Sponsor – IWMA

As fire safety technologies evolve, how do water mist systems compare to traditional sprinklers? New UK data sheds light on performance
Magazine - ask the expert - Bridging Standards

Ask the Expert – Sensitron

Marco Penso, R&D Manager at Sensitron, explores the evolving regulatory landscape, innovation challenges, and sustainability efforts shaping

Ask the Expert – F&G Detection

Eliot Sizeland, Vice President of Business Development at Fire & Gas Detection Technologies Inc., discusses the challenges of flame

Cover Story – Perimeter Solutions

Solberg Spartan offers safer, faster fire suppression—Kurt Becker of Perimeter Solutions explains how this foam is redefining frontline

Big Interview – Eng. Dana Kamal

Ahead of the NFPA Conference and Expo Fire Buyer speaks with Eng. Dana Kamal, Director, International Business Development..

Ask the Expert – Richard Wharram – The Standards Maze

Richard Wharram, Export Sales Manager at Hochiki Europe, explains how fire safety professionals can navigate Europe’s complex approval…
Picture of TLX Fire & Security products - Photo by TLX Fire & Security - FireBuyer.com

Product Spotlight: Actuator Assurance

TLX Fire & Security’s actuators meet EN 15004-1 with integrated supervision, ensuring safe installation and discharge in both standard…
Picture of Hochiki products - Photo by Hochiki - FireBuyer.com

Ensuring UL268 7th Edition Compliance Across the Middle East

Hochiki identifies compliance driven smoke detectors and multi sensors for the Middle Eastern market that ensures precision in fire…
Scroll to Top