70 Pack-level functionality The degree of self-sufficiency within modules varies, based on application requirements. While some designs prioritise fully independent modules with integrated BMS and safety features, others lean towards simpler modules that rely on centralised, pack-level management systems. This balance depends on factors such as cost, complexity and the specific needs of the vehicle platform. For example, duplicating advanced electronics across multiple, small modules can drive up costs unnecessarily, making it more practical to centralise these functions. However, some level of modular autonomy, such as temperature and voltage monitoring, is essential for effective operation and maintenance. Modular designs are increasingly geared towards sustainability and second-life applications. By embedding state-of-health monitoring and operational histories into modules, manufacturers can streamline the reuse and recycling of batteries. This data allows for accurate assessments of residual capacity and facilitates the repurposing of modules for less demanding applications, such as stationary energy storage. Designs that prioritise easy disassembly and minimal material use enhance sustainability. Lightweight, recyclable materials and standardised components contribute to more efficient end-of-life processing, aligning with global efforts to reduce the environmental impact of EV batteries. Safety mechanisms The provision of safety mechanisms within modular battery packs has seen continuous development to meet increasingly rigorous requirements, driven by tightening regulations and the desire of vehicle OEMs to stay ahead of them. Safety measures, such as thermal fuses, venting systems and cut-off mechanisms, are increasingly integrated at the module level to enhance reliability and prevent catastrophic failure. While cell size remains a significant factor influencing these designs, advancements across the board emphasise the creation of safer and more efficient systems. For smaller cells, safety features such as pressure and temperature-initiated current-interrupt devices (CIDs) and rupture valves are standard, offering robust protection against failure. Cylindrical cells particularly benefit from these integrated safety features, ensuring incidents such as thermal runaway can be mitigated early in the failure chain. For larger LFP blade cells, safety is maintained through careful structural and thermal propagation inhibition, with some designs extending these protective measures to the pack level for added redundancy. Engineers are also focusing on fusing cell connectors and incorporating design features that inhibit thermal propagation directly into the module design. This modular approach not only enhances safety, but also simplifies manufacturing and maintenance processes. Increasingly, the industry is moving towards the modular incorporation of features that historically resided at pack level, including thermal insulation and freeair volume limitation, to ensure better control over safety while maintaining flexibility in application. January/February 2025 | E-Mobility Engineering Cell form factors are influenced by chemistry, and in turn influence module design choices, with cylindrical cells often outperforming prismatic formats in high-power applications (Image courtesy of About:Energy)
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