New Material for Battery Enclosures of Electric Vehicles
2022-01-0267
03/29/2022
- Event
- Content
- In recent years, aluminum alloys have become the dominant material for battery enclosures used in battery electric vehicles (“BEV”) due to their low density. Aluminum battery enclosures, or other platform parts, typically provide weight savings of ~40% compared to equivalent commercially-used steels. The best-suited materials for battery enclosures are 6000-series and 7000-series aluminum alloys. Despite its light weight and recyclability benefits, the aluminum alloys have a crucial disadvantage if the heat generated by the battery cells raises the temperature of battery enclosures above 600°F/315°C. At the exposure of more than 300 sec at 600°F/315°C or higher, the yield strength, especially for parts that are in direct contact with the battery cells drastically drops by more than 70%, and in the critical situation of fire (~2200°F/1205°C), the batteries enclosures fail within ~5 sec, creating a paramount safety concern for BEV passengers. New high strength steel for cold stamping (“ColdStamp steel”) is an attractive alternative. ColdStamp steel is developed by AMD Corp. (see http://amdoncorp.com/coldstamp-steel ) and possesses high stiffness, high strength, and moderate ductility. A comparison of the stiffness and strength of ColdStamp steel and the strongest 7075 aluminum alloy shows that the proposed steel can substitute any aluminum alloys without sacrificing the weight of battery enclosures while increasing their durability and life-time. ColdStamp steel can be produced in electro-galvanized, hot dip galvanized, galvannealed, and aluminized forms to protect its surfaces against corrosion and high temperature oxidation. The aluminized ColdStamp steel is an attractive material for use in battery enclosure applications. ColdStamp steel can prevent failure of battery enclosures at temperatures of up to 1400°F/760°C, and withstand fires of up to 2200°F/1205°C, allowing for sufficient time to evacuate the BEV passengers in the event of an emergency. In fact, battery enclosures made from aluminum alloys cannot compete with the same weight enclosures made from aluminized ColdStamp at ambient and elevated temperatures. Furthermore, the cost of production of the aluminized ColdStamp steel is 50-60% less than the cost of production of the high strength aluminum alloys. In addition, it should be noted that the aerospace composite materials cannot be utilized for the battery enclosures effectively due to their high cost and only for applications at temperatures below 600°F/315°C.
- Citation
- Vartanov, G., "New Material for Battery Enclosures of Electric Vehicles," SAE Technical Paper 2022-01-0267, 2022, .