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hofer technology has investigated in a range of customer projects how cell preload, breathing, swelling and mechanical deformation affect the cycle life and performance of different battery cells. The objective is not simply to determine how quickly a cell ages, but rather to identify the mechanical conditions under which it can maintain its performance for as long as possible.

To support this work, the hofer technology team has developed proprietary test methods and fully programmable test equipment. During defined charge and load profiles, parameters including cell deformation, temperature, voltage, capacity and impedance are recorded. This makes it possible to determine at an early stage which mechanical constraints are best suited to a specific cell technology. Experience also shows that there is no single optimum pressure that works for every battery cell. Both insufficient and excessive mechanical forces can accelerate cell degradation. Cell chemistry, cell format, state of charge, temperature and operating profile therefore need to be considered as an integrated system. The specially developed test methodology is already being applied across a wide range of cell technologies – from NMC and LFP to next-generation solid-state cells.

A smart battery module

The insights gained from our development work and from the successful use of the new test method in numerous projects form the basis for a new generation of battery modules from hofer technology. Smart pressure control is a key feature: the battery module can adapt to the specific requirements of the cell, providing greater flexibility in terms of performance, service life and future cell technologies.

A freely programmable force map allows the pressure applied to the cells to be adjusted according to the respective operating condition. This turns what has traditionally been a fixed mechanical design parameter into an actively controllable parameter within the battery system. The high level of development already achieved allows us to support our customers in moving toward series application within a short timeframe.

How significant the effect is in each case depends on the cell technology, operating profile and initial system design. A longer battery life brings more than just technical benefits. If batteries can be used for longer, their economic value also improves. Replacement and recycling can be delayed, while residual value, total cost of ownership and resource use may also benefit. The potential applications go beyond conventional electric vehicles. High cycle life and long service life can also be important for commercial vehicles, stationary energy storage systems, marine applications, as well as future aviation and aerospace systems.

For energy storage systems using solid-state cells in particular, longer battery life and a high number of cycles can have a direct impact on the overall economics of the system. Future battery systems in vehicles will also need to support Vehicle-to-Home (V2H) and Vehicle-to-Grid (V2G) functions. V2G applications in particular can require several times as many charge and discharge cycles. This creates an additional challenge for energy storage systems based on solid-state cells. Smart pressure control helps maintain stable cell performance over a high number of charge and discharge cycles. This makes cell mechanics an important factor in the development of future battery systems.

The assessment is based on current NMC cell technologies as well as current solid-state cell technologies.