Modular lightweight starter battery (LBSB)

Our submitted patent for a modular battery housing, received the ThinkIng August in August 2021 from Leichtbau bw and was published as a starter battery application in the VDI-Z and in the lightweight construction special of ATZ.

Special design increases safety in the event of a crash

The design and the interaction of the components reduce the loads in the battery system, which has led to weight savings on the housing. In the event of a crash, its special design also allows modules arranged in parallel to move multiaxially, thus absorbing the impact energy very efficiently and protecting the cells. Thanks to this design, further cost- and mass-intensive measures for absorbing this crash energy in the vehicle can be dispensed with.

Flexible installation and minimized installation space 

Originally, the lightweight battery housing was intended to replace existing starter batteries based on lithium-iron-phosphate cells or lead-sulphuric acid batteries. For this reason, the dimensions for the base area of the battery housing were chosen so that it could replace existing solutions in the installation situation. However, due to the space-saving arrangement of the cylindrical battery cells, the height could be reduced by around a quarter. 

Thanks to the lower overall weight and smaller construction volume, new mounting concepts are also conceivable and nothing stands in the way of placing the battery in the optimum position in the vehicle. If the installation location of the battery is optimized, this can result in further cost and weight savings by shortening the cable harnesses or changing the crash-relevant structure. Other mounting concepts would open up further secondary savings, for example on the battery tray, clamping bracket and cables. 

Cost-effectiveness and modularity 

From the outset, the concept for the lightweight battery housing was aimed at economical production suitable for large-scale production. All components of the housing are manufactured using plastic injection molding. They are designed for economical production - including the use of around ten percent recycled material. Snap-on connections between the modules were provided for recycling and to further extend the service life so that all components can be replaced. The Koller Group from Dietfurt was involved in the project as a partner for the production processes.
The battery cells and the power electronics used in the project - a battery management system successfully used in motorsport by partner LITEWERKS - are mounted in holders on the inside. This structure provides additional support for the housing and creates a cooling air space for the cells and electronics. Several of these packs can be easily and reversibly combined with each other thanks to the snap connections, so that the battery can be dimensioned and repaired as required. The modular design also provides additional installation space for possible cooling units and corresponding air outlets in the holder.
In addition to its use as a replacement for 12 V starter batteries, which are also used in electric vehicles, and upcoming 48 V solutions, the lightweight battery housing with other cells is also suitable as a traction battery due to its good crash properties and control and cooling options.

Flexible installation and minimized installation space 

Originally, the lightweight battery housing was intended to replace existing starter batteries based on lithium-iron-phosphate cells or lead-sulphuric acid batteries. For this reason, the dimensions for the base area of the battery housing were chosen so that it could replace existing solutions in the installation situation. However, due to the space-saving arrangement of the cylindrical battery cells, the height could be reduced by around a quarter. 

Thanks to the lower overall weight and smaller construction volume, new mounting concepts are also conceivable and nothing stands in the way of placing the battery in the optimum position in the vehicle. If the installation location of the battery is optimized, this can result in further cost and weight savings by shortening the cable harnesses or changing the crash-relevant structure. Other mounting concepts would open up further secondary savings, for example on the battery tray, clamping bracket and cables. 

Added value through lightweight construction 

In a separate project with the BMW X5 (hybrid drive) as a reference vehicle, the additional costs for lightweight construction were estimated at around 18 euros per kilogram of weight saving in collaboration with the National Manufacturing Institute Scotland (NMIS).
Around 33 kilograms of mass and around ten liters of installation space were saved. The weight reduction is largely due to the switch to LiFePO4 technology. This is because these cells are not only lighter, but can also almost fully utilize their nominal capacity - in contrast to the lead version. A supply with a lower nominal capacity is therefore sufficient. The needs-based design of the housing concept has also contributed to the weight reduction.
However, the additional costs for the lightweight construction are offset by the lower consumption, further savings on the wiring harness and crash structures and the longer service life.

3D model of the modular lightweight starter battery

en_USEnglish