Author: Dr James Edmondson, VP Research at IDTechEx
In the Western world, the car dominates personal transport. However, in many Asian countries, the 2-wheeler (2W) is a hugely popular method of getting around. Electrification has also advanced quickly in this segment, with IDTechEx finding that 17% of 2W sales in 2023 were electric 2-wheelers (E2W). With E2Ws making up an increasingly larger share of 2W sales, their safety in terms of thermal runaway and fires is a critical topic.
We have seen much progress on this topic for the car market, but how E2Ws are used and how their batteries are designed is very different from the car market. IDTechEx’s report, “Fire Protection Materials for EV Batteries 2025-2035: Markets, Trends, and Forecasts“, finds that the market for fire protection materials in E2Ws will grow by 12 times compared to its 2024 size.
How E2W use and design differs from electric car batteries
The battery in an E2W is much smaller than that of an electric car, the vast majority of E2Ws are using a battery smaller than 4kWh, compared to that of electric cars, which averaged around 60kWh in 2024. With less energy stored, the overall severity of the fire is reduced, but several kWh is still plenty to pose a significant safety risk, especially if the fire spreads to other vehicles or structures. This concern is coupled with the fact that many owners charge two-wheelers within their homes, compared to a car that is often kept outdoors or in a garage. This scenario has unfortunately proved fatal in some previous cases.
The influence of regulation
In 2022, India had a spate of incidents and recalls relating to E2Ws and fires. Following this, the Indian government adjusted the AIS 156 standard with changes taking effect on 1st October 2022. The updates include a thermal runaway propagation test and propagation prevention should be integrated into battery design. A warning is required upon detection of a thermal event, only cells certified by the Bureau of Indian Standards (BIS) may be used, and sufficient cell-to-cell spacing must be maintained.
China has the GB standards that are also relevant for cars, requiring a 5-minute time delay between a thermal event and smoke or fire being visible outside the pack.
Prior to these standards, fire safety was not a primary concern in many battery designs, and these changes have forced battery pack designers to adopt new materials to prevent or delay the propagation of thermal runaway.
What materials are being used and how it’s changing
The use of protective materials around cells can prevent or delay thermal runaway propagation. Source: IDTechEx
Cylindrical cells are a popular choice for E2W batteries, often in the 18650 format. The cell type/geometry has a big impact on how the pack is constructed and which materials will be used. Cylindrical cells cannot be stacked as easily as prismatic cells, and hence typically require some form of encapsulation and/or cell holder.
Much of the early market used a form of encapsulant, these may have been thermally conductive to spread heat, or a thermally insulating foam to prevent heat transfer between cells. With the implementation of newer safety standards, these materials are developing and new materials are being selected. A key category is polymer cell holders that have fire protective properties, whilst a polymer solution that encases all the cells in a car battery pack might prove too heavy for the smaller E2W category, they are well suited to the application.
Material suppliers have begun developing polymers that can be injection molded to form cell holders that provide structure for the cells, maintain cell spacing, and prevent thermal runaway propagating across all the cells in the battery pack. The polymers can include glass fibers to tune the structural performance needed and some of these polymer solutions also include intumescent properties, expanding and forming a protective layer upon heating.
Phase change materials (PCMs) are another alternative seeing some application, these absorb excess heat during their phase transition (typically solid liquid) but have to be carefully formulated such that their structure does not degrade significantly during the phase transition and that it still provides fire protective benefits once it has melted.
In addition to cell holders, the choice of polymer used to encase the battery is also important, regardless of cell type or inter-cell materials, the case is the last layer of protection. This component needs to provide fire protection, but also strong impact resistance in the case of a crash.
Summary and outlook
Much like the car market, EV fire safety is critical in the E2W market. Whilst the rate of EV fires is very low, they can be devastating, especially in enclosed areas. Regulations have started to be employed in certain regions but will likely see adoption in other regions and become more stringent over time. To meet these regulations, new materials are being adopted that are especially suited to the E2W market. IDTechEx’s report on “Micro EVs 2025-2045: Electric Two-Wheelers, Three-Wheelers, and Microcars” finds that the micro EV market (including 2-wheelers, 3-wheelers, and microcars) will be worth US$90 billion by 2045. In the associated “Fire Protection Materials for EV Batteries 2025-2035: Markets, Trends, and Forecasts” report, IDTechEx finds that fire protection materials for micro EVs will exceed US$280 million by 2035, providing opportunities for various materials and suppliers.
To find out more about this IDTechEx report, including downloadable sample pages, please see www.IDTechEx.com/FPM.
For the full portfolio of electric vehicle market research available from IDTechEx, please visit www.IDTechEx.com/Research/EV.
About IDTechEx
IDTechEx provides trusted independent research on emerging technologies and their markets. Since 1999, we have been helping our clients to understand new technologies, their supply chains, market requirements, opportunities and forecasts. For more information, contact research@IDTechEx.com or visit www.IDTechEx.com.
