In many established markets, the most popular EVs are typically ‘hybrids’. They combine an ICE with an electric engine to maximize range. In other regions, such as China, where personal mobility options have traditionally been limited, fully electric vehicles (known as battery electric vehicles or BEV) dominate the market.
Batteries add weight to vehicles
One of the limitations of EVs has been the weight of the battery and extra reinforcement needed to protect it during a crash. Total weight of the battery and protection can be up to 700 kg. Positioning this mass in the vehicle has been a major challenge for carmakers. The most common approach is to keep the battery low in the vehicle.
“Advanced high strength steels (AHSS) are enabling OEMs to provide the protection required, but without adding significantly to the weight of the vehicle,” notes Jean-Luc Thirion, head of ArcelorMittal's Global R&D for Automotive. “Our offer includes Usibor®, a press hardenable steel (PHS) with strengths up to 2000 megapascals (MPa), and Fortiform® for cold stamping. Fortiform® is currently available in strengths up to 1180 MPa, but this is set to increase in 2018 with the release of Fortiform® 1470.”
Stiffness is another consideration for OEMs. To mimic the handling performance of an ICE, the stiffness of the chassis and wheels in an EV must be increased. AHSS solutions ensure stiffness performance is maintained without additional weight.
AHSS is also the preferred material to house and protect the battery in the event of a crash. The unmatched strength of the steel used in this application absorbs more energy during a crash. Thanks to their very high strength it is possible to reduce the thickness of the protection and housing systems. Intrusion resistance is still enhanced, but the space dedicated to batteries can be increased. This allows OEMs to use larger batteries and increase range – one of the biggest limitations of EVs.
“Reducing the weight of an EV by 100 kg only improves range by around 6 to 11 km depending on the size of the vehicle,” explains Jean-Luc Thirion. “The same range increase can be obtained by increasing battery capacity by 1.1 to 1.2 kilowatt hours (kWh).”