Electric Vehicle Battery Frames - The Difference Between Steel And Aluminium

The battle continues over whether to use steel or aluminium in modern car design.

This has now spilt into the electric vehicle (or ‘EV’) arena – arguably the hottest and most innovative sector of the automotive industry. Tesla was one of the earliest manufacturers to construct many of its components - from the chassis to the battery frame - in aluminium. It wasn't until their third model that Elon Musk’s company began to shift to steel, thus drastically reducing the list price of their vehicles.

This trend shows no signs of slowing.

Why aluminium over steel?

Aluminium is simply better across many categories when it comes to the auto industry. It’s much lighter than steel, which subsequently reduces the weight of each vehicle, enabling EVs to drive for longer distances on each full charge. When it comes to the battery frame, aluminium has some key benefits, too. Due to its material composition, there are more efficient ways to implement integrated cooling features which cool the battery itself.

Aluminium also handles extremely cold temperatures much better than steel, thus maintaining its shape and being a better overall conductor of temperature. In addition, aluminium provides a great balance between strength and modular design. It’s extremely strong, yet flexible enough to be able to fit any type of custom battery frame housing.

It’s safer, too. If an accident takes place, aluminium is also leakproof thanks to friction stir welding, protecting those in the crash from leaking battery acid. It also absorbs more of the impact than other materials such as plastic (which often shatter).

Why steel over aluminium?

Steel does have its advantages for car battery frames. Although this material adds significant weight, it’s worth remembering that in this use case, it’s essentially housing a potentially explosive or dangerous item (the battery).

Steel remains far safer in this regard, compared to aluminium - no matter how quickly the latter appears to be catching up. It’s also built to resist extremely high temperatures, so any fires are either isolated within the frame, or the frame itself protects the battery from further damage.

Steel also provides better protection when driving. Remember – it’s housing the powertrain for the entire vehicle, therefore if the driver hits a pothole, or something else that could damage the undercarriage of the vehicle, the battery will be sufficiently protected. It’s also still significantly cheaper to purchase and shape into battery frames. The raw material cost of aluminium alone usually comes out to around three times that of steel. 

Aluminium and steel as sustainable options

When considering the overall environmental impact of EVs, both aluminium and steel are easily recycled. Steel only wins this particular battle by a small margin, because it is one of the easiest materials on earth to recycle due to how it's manufactured. Aluminium, thanks to consistent development and smarter manufacturing techniques, is also an admirable competitor when it comes to sustainability.

Is there room for both?

Absolutely! There’s a trend to move closer towards aluminium and its advanced configurations for electric vehicles and, in particular, battery frames. Only time will tell if we ever stop using steel in our vehicles, but one thing is for sure – aluminium still has some catching up to do.

If we’ve sparked any questions today, don’t forget you can contact the Flowdrill team directly - we’d love to hear from you.