72 to be more cost-effective and practical. Modular design also has an impact on fault isolation strategies. By integrating thermal fuses and cut-off mechanisms at module level, defective cells or modules can be isolated quickly, preventing failure propagation and improving the overall safety profile of the battery. Venting systems and pressure-relief mechanisms ensure any failure is contained and managed effectively, reducing the risk of damage to adjacent components. Performance and efficiency The inherent flexibility of modular battery packs is a significant advantage, allowing manufacturers to scale systems to meet the diverse requirements of a wide range of applications, from compact EVs to heavy-duty commercial trucks. However, this flexibility must not come at the expense of performance or efficiency. Modular designs must carefully consider the trade-offs involved in incorporating additional structural and thermal management components. By focusing on common design elements and scalable architectures, manufacturers can reduce production complexities and accelerate time-tomarket for new products. This approach supports future-proofing, as modular systems can accommodate emerging cell chemistries and technologies with minimal redesign. Large-format LFP prismatic cells, while mechanically simple and costeffective, pose challenges in terms of packaging and state estimation due to their size and unique characteristics. Advances in BMS algorithms are addressing these issues, enabling more accurate predictions of cell behaviour and enhancing the reliability of modular systems. These innovations highlight the importance of harmonising design and control advancements to deliver optimised solutions. Getting specific Designing modular battery packs for specific EV applications requires a careful balance of technological trade-offs and innovations. One critical consideration lies in creating modules versatile enough for integration into various vehicle architectures. Smaller modules offer greater flexibility, but compromise specific energy density, volumetric efficiency and cost-effectiveness. Larger, standardised modules achieve better scale efficiencies and performance, but might not fit as seamlessly into specialised platforms. The decision-making process for module size and design benefits from extensive market studies and optimisation to maximise crossplatform utility, particularly in sectors with smaller production volumes, such as commercial vehicles. The configuration of modules also has an impact on integration complexity. Adopting a universal cooling architecture is challenging as different vehicle types demand varying thermal management solutions, which highlights the need for early-stage design integration, where strategies can exploit shared heat sources, such as motors and inverters, to enhance efficiency. Similarly, modular designs benefit from standardisation in cell sizes, which balances performance with cost and simplifies integration. Another aspect of modular battery development is the trade-off between energy density and installation space. A universal approach introduces compromises. Standardised modules are inherently less space-efficient for niche applications, but their cost advantages, derived from economies of scale, make them an attractive option. Modular designs tailored for scalability face challenges in maintaining optimal energy density, but despite that they often achieve better gravimetric efficiency due to reduced weight in downsized configurations. Future directions BMSs are evolving alongside modular technologies, reflecting a growing demand for smarter and more integrated control mechanisms. Two main architectures have emerged. The first uses a separate ‘master’ controller outside the modular pack, while the second gives every module ‘master’ capability. The first architecture offers greater flexibility and reduced system costs for multiple module applications. While BMSs have typically always been modular, more robust communication strategies are evolving, Product focus | Modular batteries January/February 2025 | E-Mobility Engineering Colour-coded display of heat distribution among cells in a module, illustrating the value of embedding at least some sensing capabilities (Image courtesy of About:Energy)
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