71 Modular batteries | Product focus Thermal management Thermal management is critical in battery modules to maintain optimal operating temperatures and extend battery life. The industry has seen a shift towards designs that integrate mechanical stability and cooling functions. One approach involves using extruded profiles within the module structure that act as both cooling systems and structural backbones. This dual-purpose design minimises the complexity of thermal systems while supporting modularity by allowing straightforward adjustments to accommodate varying pack sizes. Options for thermal management include passive and active systems. Modules equipped with passive thermal management rely on efficient material choices and structural configurations to dissipate heat naturally. Active systems, on the other hand, employ liquid glycol or refrigerated air cooling to regulate temperature more precisely, and they are often integrated autonomously within the modules, reducing dependency on the pack-level infrastructure. For applications requiring high precision, individual cooling plates for each module are gaining traction. This modular thermal approach enables better customisation of cell arrangements within the module and supports designs that cater to unique chassis configurations. However, this flexibility often introduces complexity in interconnection and plumbing; a tradeoff that engineers must address during the design phase. In configurations with multiple cooling plates, external connections are prioritised to streamline assembly and maintenance processes. Energy density The modular design of battery packs inherently affects energy density due to the additional packaging materials and components required. These include void spaces, compression plates and other structural elements, which, while critical, detract from the battery’s volumetric efficiency. Pouch cells, for instance, require compression foam or plates to counteract expansion forces, which reduces the overall energy density of the module. However, these components are necessary for maintaining structural integrity and operational safety. While volumetric energy density may be compromised, gravimetric energy density can improve in some modular systems due to reduced weight in less dense configurations. This trade-off is particularly evident in applications where battery capacity needs to vary, such as in automotive platforms ranging from entry-level to premium. The modular approach allows engineers to customise battery configurations without extensive re-engineering, providing flexibility across different use cases while ensuring a baseline level of performance and safety. In standardising cell sizes, such as the 21700 format, manufacturers can strike a balance between energy and power density. This minimises development time and costs while allowing for the rapid adoption of new cell chemistries or technologies as they emerge. Such modular designs facilitate scalability and adaptability, ensuring systems remain competitive as requirements evolve. Monitoring and diagnostics The move towards modularity has not only influenced thermal and structural considerations, but also driven advancements in BMSs. Modern ones incorporate cell-level balancing and diagnostics to predict potential failures and mitigate issues before they escalate. Sensors and control algorithms are critical components, providing real-time insights into the state of health and charge for individual cells and modules. This supports preventative maintenance strategies and extends the overall lifespan of the pack. Incorporating these safety and monitoring mechanisms at module level simplifies diagnostics and enhances modular autonomy. However, a balance must be struck to avoid overengineering. Excessive duplication of monitoring systems within each module can lead to unnecessary cost increases and complexity. Instead, a tiered approach, where essential safety measures are implemented at module level and overarching controls are managed at pack level, has proven E-Mobility Engineering | January/February 2025 Kreisel technician connects pack wiring to a BMS board on one of its immersion-cooled modules, developed for off-highway applications (Image courtesy of Kreisel Electric)
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