01 A New Breakthrough in Hydrogen-Electric Safety: Coupled Fire Test of Onboard Hydrogen Systems and Traction Batteries

As an important pathway for clean energy transportation, hydrogen fuel cell vehicles are gradually moving toward large-scale deployment. However, their core safety challenges—particularly the coupled risks between onboard hydrogen systems and traction batteries under extreme accident scenarios—remain a key focus of industry concern. If a traction battery undergoes thermal runaway, could it trigger a cascading reaction in the onboard hydrogen system? Where exactly do the safety boundaries of hydrogen–electric hybrid power systems lie?

By establishing a coupled fire testing platform for onboard hydrogen systems and traction batteries, CATARC Hydrogen Energy Team conducted coupled fire tests to investigate the effects of traction battery thermal runaway on the surface temperature of onboard hydrogen systems, the internal temperature and pressure of hydrogen storage cylinders, and  safety venting behaviors. The results provide a reference for the comprehensive safety performance evaluation of hydrogen-electric hybrid power systems under extreme thermal runaway scenarios.

02 Key Experimental Conclusion: Onboard Hydrogen Systems Demonstrate Reliable Safety Pressure Relief Capability Under Extreme Fire Conditions

During the test, the traction battery was exposed to an open-flame environment to simulate the post–thermal runaway fire scenario. Monitoring data showed that, under direct flame impingement from the battery side, the surface temperature of the onboard hydrogen system gradually increased. After more than 300 seconds, the TPRD (thermally activated pressure relief device) reached its safety threshold of 125 °C and actuated as designed, allowing the high-pressure hydrogen inside the storage cylinder to be safely released. Throughout the entire test, no explosion, cylinder rupture, or other abnormal events were observed.

This result clearly conveys a key message: under extreme fire conditions triggered by battery thermal runaway, the onboard hydrogen system is still able to achieve controlled pressure relief in accordance with its safety design, effectively preventing the coupling and amplification of “electric–hydrogen” risks. This represents not only a technical validation, but also strong support for the safety design philosophy of hydrogen–electric hybrid systems.

At present, hydrogen fuel cell vehicles worldwide are still at the demonstration and early deployment stage, and safety remains the lifeline of sustainable industry development. Based on real-world risk scenarios, this test was conducted around a typical failure modes—“battery thermal runaway -- open-flame exposure -- onboard hydrogen system response.” Its significance lies not only in the safety validation of individual products, but also in providing the industry with referenceable safety testing methodologies, risk assessment dimensions, and system-level protection strategies.

The results demonstrate that, through appropriate system layout, material selection, and coordinated safety device design, hydrogen–electric hybrid power systems are capable of withstanding extreme thermal runaway events.

This coupled fire test involving the onboard hydrogen system and the traction battery is far from an isolated technical validation. Rather, it represents a snapshot of CATARC Hydrogen Energy Team’s long-term commitment to hydrogen safety. From managing hydrogen–electric coupling risks in automotive applications, to hydrogen safety practices in rail transit and marine equipment, and further to safety testing in special scenarios such as underground parking garages, tunnels, and hydrogen production facilities, the team has consistently pursued a full-scenario, full-chain approach. Systematic experimental research has been conducted across the entire hydrogen safety chain—leakage, dispersion, combustion, and explosion. These efforts have not only generated invaluable safety data and practical insights for the industry, but have also laid a solid safety foundation for the hydrogen sector’s transition from pilot demonstrations to large-scale, commercial deployment.

2026 International Hydrogen and Fuel Cell Vehicle Congress & Exhibition (FCVC 2026)