The SEE‑2L project aimed to establish safe operating procedures for high‑energy electrochemical storage systems used in second‑life applications. A key objective was to investigate the conditions that lead to thermal runaway, its propagation through battery modules, and to develop measures for containment or suppression. To this end a technical‑scale demonstrator was built on the “Testgelände Technische Sicherheit” of the Bundesanstalt für Materialforschung und -prüfung (BAM). The demonstrator enabled controlled experiments with individual battery modules and complete battery packs, allowing the team to observe temperature evolution, time scales, and chain‑reaction dynamics during runaway events.
In the laboratory phase, the Institute for Apparatus and Environmental Technology (IAUT) performed detailed measurements of gases released during thermal runaway of 2.5 Ah pouch cells at various states of charge (SOC). Fourier‑transform infrared spectroscopy revealed that the volume concentration of carbon monoxide increased with SOC, reaching a maximum of 90 353 ppm – essentially the lower explosion limit for CO. Relative mass loss data correlated with SOC provided an estimate of the total gas volume released. These results confirmed that higher SOC levels significantly raise the risk of hazardous gas emissions during runaway.
Temperature measurements during full‑scale demonstrator tests showed that runaway can reach peak temperatures exceeding 400 °C within seconds, and that the heat propagates rapidly from a single cell to adjacent modules. Numerical simulations, developed in parallel, reproduced the observed temperature profiles and predicted the spatial spread of the runaway. The simulation model incorporated the measured gas composition and mass loss, enabling the team to assess the effectiveness of different heat‑absorbing layers. Experimental trials with such layers demonstrated a measurable delay in propagation, providing a practical mitigation strategy.
Early detection of runaway was addressed by monitoring voltage, temperature, and gas composition in real time. The team identified characteristic signatures that precede full thermal runaway, allowing for timely intervention. Fire suppression experiments evaluated various extinguishing agents and tactics. Results indicated that certain foam and dry‑chemical agents could suppress the fire before it fully developed, while water spray was less effective due to the high temperatures involved.
The project also examined the impact of a battery‑pack fire on surrounding building structures. Finite‑element analyses of heat transfer to building materials suggested that, without adequate fire‑resistance measures, structural integrity could be compromised within minutes. Based on these findings, the team produced safety guidelines for the design of stationary storage installations, including recommendations for fire‑resistant barriers and ventilation strategies.
Training and safety concepts for fire‑fighting personnel were derived from the experimental data. The project produced handbooks and simulation modules that illustrate the progression of a battery fire and the appropriate suppression techniques. These materials were presented at the EUSAS 2023 conference in Frankfurt and are intended for use by emergency responders.
Collaboration was central to the project’s success. The consortium comprised the Ostfälische Technische Hochschule Magdeburg‑Stendal (OVGU), BAM, the Vfdb (a partner responsible for outreach), the Institute of Firefighting North Rhine‑Westphalia, and other associated partners. OVGU contributed laboratory experiments, demonstrator construction, simulation development, and the creation of safety and training materials. BAM provided the test site, technical support, and access to its safety testing facilities. The Vfdb coordinated public relations and knowledge transfer to end users. Regular biannual consortium meetings ensured that all partners remained aligned on objectives and progress. Funding was provided by the European Regional Development Fund, supporting the project’s research and development activities. The project concluded in October 2023, delivering a comprehensive set of technical findings and practical safety recommendations for the deployment of second‑life battery storage systems.