A bodyguard made of steel: The selectrify® battery housing for e-cars
14.06.2020 I Güllü Beydilli
Those who rely on electric mobility do not follow a fast-moving trend, but invest in a sustainable future. Our experts have set their attention on the heart of the electric car and sought out the ideal material to protect the batteries, which are as expensive as they are sensitive. The result: the selectrify® battery housing made of high-strength steel - safe, cost-effective and sustainable.
As part of the selectrify® initiative, thyssenkrupp Steel has developed a battery housing made of steel which significantly improves fire safety in electric cars, is up to 50% cheaper to produce and generates only around half as much CO2 emissions as comparable battery housings made of aluminum. Patrick Tlauka, project manager of the selectrify® initiative at thyssenkrupp Steel, sees great potential for electromobility in the use of ultra-high-strength steels: “Our concepts enable us to meet a wide range of requirements. Thanks to different design methods, we can offer concepts that can absorb very high reaction forces and allow virtually no deformation, but also softer structures with intentional crumple zones that absorb impact energy.”
In an emergency, the selectrify® battery housing provides minutes – vital for the driver and passengers
A sturdy and fireproof battery case is by no means only used to protect the battery itself. Damage to the battery cells can cause fires, which can also be dangerous for the occupants. Today’s lithium-ion batteries are extremely powerful, but also highly sensitive. Battery cases made of aluminium are not very resistant to flames and intense heat. In fire tests, the material collapses after only 30 seconds. In an emergency, however, every second is crucial. It’s a good thing that battery housings made of steel remain far below their melting point even in battery fires and protect the passenger cell safely.
The selectrify® battery housing made of high-strength steel ensures comprehensive protection of the battery modules against crash influences. This protective function serves to prevent battery fires from occurring in the first place.
A battery housing must be able to do this
The battery housing has the central task of protecting the battery modules. They are the interface between the drive system and the structural element and are therefore one of the most important components within an electric car. To ensure efficient protection, it must be stable enough to protect the battery module from damage in the event of an accident. The built-in cooling system also prevents the battery module from overheating. Finally, the battery housing must be extremely corrosion-resistant to protect the batteries for many years despite environmental influences.
Less CO2 in the entire production chain
One of the biggest challenges of electric mobility is to produce electric vehicles in a continuously more sustainable and climate-friendly way. It is true that they no longer need fossil fuels for their propulsion. However, CO2 emissions are shifting from use to production – and here battery modules and their housings play a key role.
A detailed life cycle analysis has recommended steel as a sustainable material for electric car battery housings. Up to two-thirds fewer greenhouse gas emissions are generated in the production of a steel battery case compared to the production of battery cases made of aluminum.
Up to 50% lower production costs
Another advantage is the low costs. For an analysis, a production of 200,000 vehicles per year over a period of seven years was assumed. Data on material and production costs as well as costs for component manufacture, body-in-white production, leak testing and corrosion protection were included in the calculation. The result: battery housings made of steel are up to 50% cheaper to manufacture than housings made of aluminum and achieve a similar weight level.
“We have a high cost advantage – simply because of the material”, Patrick Tlauka compares battery housings made of aluminum with the selectrify® battery housing: “For a comparable weight, the cost of aluminum is three times that of steel”.
More range with steel housing?
High-strength steels are stable and can be produced with very thin walls. This is a decisive advantage for electric vehicles, because if the battery housing takes up less space, there is room for a larger battery. “For electric cars, a larger battery means above all more range,” explains Tlauka. “A thin-walled, light and compact design of the battery housing is important to meet the concern of many end users that they will be left behind with an empty battery”.
The selectrify® battery housing paves the way for electric car manufacturers to improve the range and safety of their electric cars and to convince their customers to take the step into this forward-looking technology. The developments in electric mobility remain exciting. The experts at thyssenkrupp Steel are definitely at the forefront when it comes to making the electric car fit for everyday use.