Researchers from Switzerland, Germany and France have examined in detail what happens when the battery module of an electric vehicle (EV) catches fire in an enclosed space.
A dry bang and then it starts: a battery module of an electric car is set ablaze in the Hagerbach test gallery. A video of the test (below) shows the energy contained in such batteries: meter-long flames hiss through the room and produce enormous quantities of thick, black soot. Visibility quickly approaches zero. After a few minutes, the battery module burns out. Ash and soot have spread throughout the room.
The experiment, financed by the Swiss Federal Roads Office (Astra), took place in December 2019 and the evaluation is now available. "In our experiment, we were thinking primarily of private and public operators of small and large underground or multi-storey car parks," says project manager Lars Derek Mellert from Amstein + Walthert Progress. "All these underground structures are increasingly being used by electric cars. And everyone asks themselves: What happens if such a car catches fire? What are the health risks for people in the vicinity? And also: What effects does such a fire have on the operation of the plant?"
Mellert developed three test scenarios with the support of battery researcher Marcel Held and corrosion specialist Martin Tuchschmid from Empa. Other participants were experts from the Hagerbach AG test gallery and the French "Centre d'études des tunnels" (CETU) in Bron. Among other things, the researchers installed test surfaces in the fire chamber, on which the soot was deposited. After the test, these surfaces were chemically analysed and also stored in special rooms for several months to detect possible corrosion damage.
The Swiss researchers tested three realistic scenarios: A fire in an enclosed space, a fire in a room with a sprinkler system and a fire in a road tunnel with ventilation.
The first scenario involved a fire in a closed parking garage without mechanical ventilation. A parking area of 28 x 28 metres and a floor height of 2.5 metres was assumed. Such a parking floor would have an air volume of 2000 cubic metres. The fire of a small car with a fully charged battery of 32 kWh is assumed. For reasons of test economy everything was reduced to 1/8: A fully charged battery module with 4 kWh capacity in a room with 250 cubic meters of air volume was set on fire. The tests examined how the soot settles on tunnel walls, surfaces and on protective suits worn by firefighters present, how toxic the residues are and how the fire site can be cleaned after the event.