Lighter and safer: an aluminium-foam battery case

The challenge when constructing electric vehicles is to reduce deadweight using lightweight design and thus increase the vehicle’s range. Now, the company Havel metal foam GmbH has developed a battery box that is not just lighter than conventional battery cases. It also provides improved protection for the battery.

The battery casing in an electric car must fulfil several requirements: The material must be high strength and, as batteries are usually built into vehicle floors, the construction as a whole must have a good crash behaviour. Even just an impact on the undercarriage can damage the battery. The casing should also facilitate temperature regulation because the performance of lithium ion batteries decreases in frosty conditions and the battery ages faster at temperatures above 30 degrees. Most importantly, the battery casing should be very light in order to minimise the effect on the vehicle’s range.

Havel metal foam GmbH from Brandenburg an der Havel has now, with the assistance of lightweight design technology, developed a battery box that better fulfils these requirements than conventional battery cases. The company won the Brandenburg Innovation Award for Metal 2019 for this innovation.

Aluminium sandwich—an innovation

The core of the innovation is the construction of the battery case from aluminium foam sandwiches. Aluminium cover sheets enclose aluminium foam on both sides. The aluminium foam was developed by the company itself in cooperation with a science partner. The aluminium foam has a thickness of only 0.7 grams per cubic centimetre. Battery cases with aluminium foam are thus much lighter than ordinary battery cases that are usually made of solid aluminium or steel. These cases are also doubly sustainable: The metal foam is 100 per cent recyclable.

The battery box from Havel metal foam also exhibits better crash and safety behaviour. Conventional battery cases made of solid aluminium or steel deform under pressure, which damages the battery. The new battery cases get around this problem thanks to their sandwich-like structure. In the event of impact on the cover sheet, the pressure is distributed across the porous material of the aluminium foam. This does not, however, lead to a deformation of the second cover sheet.

The baseplate of the battery case is installed as a continuous sandwich in vehicle undercarriages. The installation of further sandwiches as place holders and crash absorbers between the battery cells ensures additional safety.

Safety soon in series production?

Pipes for regulating temperature are welded into conventional battery cases. However, welding seams are a potential weak spot because they can break. Havel metal foam GmbH has found a solution that avoids welding. Stainless steel pipes are placed in the aluminium foam. Together they form a direct metallurgic bond. This method is also more economic, as additional welding work by man or machine is not required.

The aluminium foam battery box is suitable for all vehicle sizes. The Brandenburg company is already negotiating with various vehicle manufacturers so they can mass produce their innovative battery case.