New research has been published by the government offering greater insight into the safety of e-bike and e-scooter lithium-ion batteries, chargers, and e-bike conversion kits
Published on 29 January 2025 by the Office for Product Safety and Standards (OPSS), the research and analysis was independently carried out by Warwick Manufacturing Group (WMG) at the University of Warwick with a view to improving the government’s understanding of the “complex issues and safety challenges” presented by Personal Light Electric Vehicles (PLEVs), including the risks associated with unsafe e-bike and e-scooter batteries and chargers.
Combining real-world evidence with scientific data from the UK and overseas, the report addressed the following safety considerations:
- how battery failures occur during real-world use and environments, including scenarios of foreseeable misuse or modification
- the types of processes and materials used in product manufacture that achieve safer design and safer use of lithium-ion batteries
- potential shortcomings in technical requirements in product standards that have not kept pace with technological innovation.
With the use of PLEVs having grown rapidly over the last decade, so too have the number of battery-related fire incidents in the UK. According to OPSS, in 2023, there were almost 200 fires involving lithium-ion batteries, chargers, and conversion kits, with 10 fatalities. Much of the existing data has been collated by the London Fire Brigade (LFB), which has long been advocating for better safety standards for e-bikes and e-scooters through its #ChargeSafe campaign, with WMG noting that “UK-wide data has not been collated for long enough or with sufficient detail to be analysed”.
Highlighting inconsistencies around the standards applicable to e-scooter batteries versus e-bike batteries, WMG also shared the findings of its inspections and testing of several e-bike and e-scooter batteries available on the UK market, covering differing price points. Under laboratory conditions, thermal runaway of a battery was achieved through mechanical abuse, such as crushing or penetration of cells; thermal abuse, referring to over-heating; and electrical abuse by overcharging (over-voltage or charging over-current) or over-discharging (under-voltage or discharging over-current).
WMG found there was a “clear correlation between the price-per-unit-of-energy of PLEV batteries and the safety outcomes”, with tests showing that “PLEV batteries with a higher price-per-unit-of-energy, which had better designed safety circuits, more sophisticated electronics and were better manufactured, successfully prevented thermal runaway by a combination of passive and active protection systems”.
The report stated: “Considering the high severity of thermal runaway, even with a low or limited likelihood of it occurring, cells and batteries must be designed based on the assumption that single-cell thermal runaway will happen.”
As such, steps should be taken to ensure that the battery management system (BMS) has been designed and manufactured to minimise the likelihood of thermal runaway; ensure detection of the potential causes of thermal runaway; act to prevent thermal runaway when potential causes are detected; mitigate against single points of failure; and mitigate against the severity of thermal runaway when it does occur.
Recommending actions to be taken by the government, WMG called for improvements to and better consistency in the legislation and standards applicable to PLEV batteries, ranging from cell production quality to the abuse testing methodology and functional safety; collection of incident data; consumer advice; and increased obligations and penalties for companies selling PLEVs and their batteries.
“If these suggestions are acted on by the relevant parties in government, standards bodies, manufacturers, and other stakeholders, WMG believes that the unacceptably high level of PLEV fires can be reduced over time. There is, however, no quick fix, due to the large number of products already in the hands of consumers”, WMG concluded.
Commenting on WMG’s report, OPSS said: “This has been a significant undertaking by WMG using its specialist expertise and technical capabilities to undertake analysis of battery safety issues, product inspections, and conduct laboratory testing.”
As previously reported by the FPA, in December 2024, OPSS published new statutory guidelines for businesses producing and distributing lithium-ion batteries for e-bikes.
Acknowledging that “tackling the risks related to fires involving e-bikes and e-scooters remains a priority” for the government, the department also shared an update of its priorities going forward, which include the development of a PAS to cover the safety of lithium-ion batteries in collaboration with the BSI and other stakeholders, drawing on the findings in the WMG research.
A spokesperson for WMG said: “We are delighted to have had the opportunity to assist OPSS to achieve a deeper understanding of the root causes of these battery fires.”
You can view the full report here.
You can also read our interview on battery safety testing with Dr Simon Jones, Principal Engineer for WMG at the University of Warwick, which appeared in the February 2024 issue of the Fire & Risk Management journal, here.