Fire protection for battery boxes

Materials specialists for battery boxes conducted fire protection tests in electric cars at voestalpine.

Hot challenge, cool solution

Safety and the protection of occupants in the case of a fire are hotly debated topics when it comes to electric (BEV) and hybrid (PHEV) cars. Battery boxes play a central role in this discussion. In our efforts to develop optimum solutions, data from practical tests provide important information. With a self-conducted fire test, voestalpine provides refractory data and material expertise, and the core message is this: Steel can save lives!

What will be the norm tomorrow?

Fire protection in the electric car sector is still in its infancy. Standards such as UN ECE R100 or GB/T 31467.3 regulate the safety requirements for battery boxes, including the integrated fire protection. Temperatures and temperature curves are not mentioned. The standards stipulate only the following: In the event of fire, it must be ensured that the occupants have sufficient time to exit the vehicle. It is foreseeable that, as technology continues to develop, legal standards to ensure fire protection will also continue to evolve. voestalpine is helping to ensure that OEMs are on the safe side, including with respect to the future requirements of electromobility.

High level of expertise at voestalpine

The melting point of steel is very high. As a steel manufacturer, voestalpine has a great deal of experience and expertise in the high-temperature range. The company is a leading developer of innovative high-strength steels for lightweight automotive designs. With their crash performance, formability and weight advantages, these special steels are also recommended for battery boxes.

The proof of the pudding is in the simulation

To deepen its steel expertise for the mobility of tomorrow, voestalpine has establish a high level of expertise in the field of battery boxes. This includes fire protection simulations that have also been compared with a real fire test. The battery box prototype was tested without battery modules in an external fire. This strengthened the database for mechanical components, and a better understanding was gained of the processes.

Fire and flame for optimum solutions

The next generation of voestalpine employees was also included in the data collection process in that the voestalpine apprentice training center supplied the test set-up. The voestalpine fire department at the Linz production site was responsible for guaranteeing safe procedures.

Test and test object

The test object was the prototype of a battery box in frame design that was based on the specifications of the UN ECE R100 approval standard and was manufactured in-house. The dimensions were 800 x 600 mm based on 120 x 40 mm rectangular profiles that were tightly welded to a 1.3 mm bottom sheet and a 0.5 mm top sheet. The following steel grades were used:

  • HCT450X, dual-phase steel, EN 10338
  • CR1030Y1300T-MS, martensitic steel, VDA 239-100
  • S315MC, thermomechanically hot-rolled steel strip for cold forming, EN 10149
Setup of a fire protection test pursuant to UN ECE R100.
Fire protection test with direct flame from a gasoline fire pursuant to UN ECE R100.

The aim of the test was to obtain data from behavior of the box in an external fire. Nine temperature sensors were attached to the outer and inner surfaces of the box. The prototype was positioned over a gasoline fire, and the measurement data were collected.

Battery box fire test: The temperatures generated by the fire and measured with temperature sensors are no problem for steel.
The resulting temperatures, measured with nine sensors, were no problem for steel. The picture shows the temperature curves of three sensors.

Steel can save lives!

The box survived the test undamaged and unchanged, even at a temperature of roughly 600 °C. While alternative material concepts reach their limits at these temperatures and begin to melt, steel - with a melting point of over 1,400 °C - is unimpressed. Steel is simply a "cool" solution - even if battery cells would burn, i.e. in case of a fire inside the battery box. According to the literature, temperature peaks of up to 1,200 °C can occur in these cases, which are still far below the steel melting temperature. Steel as a material for battery boxes can save lives.

voestalpine support

Please contact us. voestalpine will be happy to provide data and comprehensive support:

  • Material expertise
  • Wide range of optimized steels 
  • Expert steel recommendations
  • Material expertise for common battery box designs (tray, frame and steel-aluminum hybrid designs)
  • Expertise in the fields of corrosion, welding and joining
  • Simulation model data for battery box designs

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