Thermal propagation: a major advancement in electric vehicle safety

With the rapid growth of electric vehicles, battery safety has become a key issue for the automotive industry. A major update to the European UNECE R100 regulation, which came into force in September 2025, will strengthen these requirements. It will gradually become mandatory for new vehicles starting in September 2027, pending official publication by the European Commission.

An evolution of existing tests

These new requirements are not based on entirely new tests, but rather on a more structured and reinforced framework for tests already carried out on automotive batteries. The objective is to harmonize methods and ensure high levels of safety. These procedures may also be extended to non-automotive batteries.

Among the proposed methodologies:

• Tests using a fast external (or internal) heating element: application on the surface (or insertion within a cell) of a thermal device to induce rapid heating and observe thermal propagation.
• Nail intrusion test: simulation of a battery puncture reaching a cell, in order to trigger an internal short circuit.

A clear objective: occupant safety

The main objective of this regulation is to protect occupants in the event of battery thermal runaway while the vehicle is in active driving mode.

In practical terms, the requirements aim to ensure a sufficient delay (minimum 5 minutes) before any critical event (explosion, uncontrolled propagation), allowing passengers to safely exit the vehicle.

Testing capabilities already in place

These tests can be carried out at UTAC sites in Linas-Montlhéry and Millbrook, with the possibility of leveraging a network of specialized partners.

UTAC is also fully engaged in discussions with ecosystem stakeholders, notably through the PFA (Automotive Platform), in collaboration with battery manufacturers and authorities such as the DGEC.