TGM special: Modular Lightweight Starterbattery

December 7, 2021

By Florian Wätzold

The concept

Besides our passion for analysing existing vehicles in our lightweight garage, we also get creative ourselves designing new lightweight concepts. Together with our partners, the National Manufacturing Institute Scotland, Litewerks and the Koller Group, we have developed a modular modular lightweight starter battery to replace conventional heavy lead lead batteries. The starting point is the technology change to lithium iron phosphate, as the stable voltage plateau above the capacity enables efficient use.

The idea

Starting with lithium iron phosphate cylindric cells, which are accommodated in the cell holder at their stiff end points, the housing was designed accordingly. This accommodation allows the cell surface to be cooled. The cells are arranged in a pack-tight manner in the cell holder and cut-outs provide installation space for cable routing, the battery management system and other components.

The cell holders support the enclosure and thus reduce the required wall thickness, as forces can be transferred ideally. The prismatic shape of the enclosure also increases its inherent rigidity. In an application with parallel housings, the slopes allow the batteries to slide on top of each other and thus reduce the crash load.

The modular design with a high number of of common parts opens up economies of scale and enables dimensioning according to the requirements. For an application with only one module a cover is placed on the module, whereas a connector combines two modules. When mounting with a clamp, forces are also transmitted via the connector. The snap connections allow to open the battery without destroying it.

The demonstrator

The first demonstrator of the modular lightweight starter battery was created from stereolithographically manufactured housing parts, a battery management system and filled dummy battery cells. To ensure optimal production, the wall thicknesses were adjusted and the snap connections were glued.

One module in the version shown corresponds to the equivalent of a 70 Ah lead starter battery. Two modules have the same length and width of a 90 Ah lead-acid battery and offer a standard-compliant installation.

The lightweighting

The weight saving on the 2016 X5 Hybrid (F15) reference vehicle, according to the casestudy performed, amounts to over 33 kg compared to the baseline condition and can be increased to over Effects to be increased to over 40 kg. Also, 10 L of installation space is freed up is freed up and the service life is tripled. The lightweight construction costs at the reference fall from 23.1 and 18.7 € respectively, including the secondary secondary effects to 15.6 and 12.5 € respectively.

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