TGM Special : Modular lightweight starter battery

Published on

07.12.2021

The concept

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

The idea

The housing was further designed on the basis of lithium iron phosphate round cells, which are held at the rigid end points in the cell holder. This mounting enables the cell surface to be cooled. The cells are arranged pack-tight in the cell holder and cut-outs provide installation space for cable routing, battery control and other components.

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

The modular design with a large number of identical parts opens up economies of scale and enables dimensioning according to requirements. For an application with just one module, a cover is placed on the module, whereas a connector combines two modules. When mounting with a clamping bracket, forces are also transmitted via the connector. The battery can be opened non-destructively using the snap-on connections.

The demonstrator

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

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

The lightweight aspect

The weight saving on the 2016 X5 Hybrid (F15) reference vehicle amounts to Case study over 33 kg compared to the initial state and can be increased to over 40 kg through secondary effects. It also frees up 10 liters of installation space and triples the service life. The lightweight construction costs of the reference fall from 23.1 and 18.7 € including the secondary effects to 15.6 and 12.5 € respectively.