Electric vehicle battery pack design represents a complex engineering challenge that balances energy density, power delivery, thermal management, and structural integrity. The architecture of these systems directly impacts vehicle performance, range, and safety, requiring careful optimization of electrical, mechanical, and thermal characteristics.

Module configurations form the foundational building blocks of EV battery packs. Traditional designs use modular assemblies where individual cells are grouped into modules, which are then combined to form the complete pack. A typical module contains between 12 to 96 lithium-ion cells, arranged in specific series and parallel configurations. For example, many automakers use 12-cell modules arranged in 3 parallel strings of 4 series-connected cells, creating a nominal voltage around 48V per module. These modules incorporate their own busbars, cooling channels, and structural frames before integration into the larger pack. The modular approach offers manufacturing flexibility and easier serviceability but adds weight and reduces overall energy density due to redundant components.

Series and parallel cell arrangements determine the pack's voltage and capacity characteristics. Series connections increase voltage while maintaining capacity, critical for meeting the 350-800V operating ranges of modern EVs. Parallel connections boost capacity and current capability while keeping voltage constant. Most commercial packs use a combination approach. For instance, Tesla's 4680 cell-based packs employ a 46mm diameter cell with approximately 4.8V nominal voltage per cell. Arranging 108 cells in series yields roughly 518V nominal pack voltage. Parallel groupings of these series strings then determine total capacity, with typical configurations showing 4 parallel groups in long-range vehicles. This arrangement must carefully balance current distribution to prevent cell imbalance during high-power discharge.

Structural integration approaches have evolved significantly in recent years. Conventional designs mount completed battery modules to a vehicle's underbody with separate structural and protective elements. Newer cell-to-pack architectures eliminate the module level, directly integrating cells into the pack structure. BYD's Blade Battery exemplifies this approach, using long LFP cells arranged in an array that provides both energy storage and structural reinforcement. The design improves volumetric energy density by 50% compared to modular approaches while reducing part count by 40%. Cell-to-chassis designs take integration further by making the battery pack an integral load-bearing element of the vehicle structure. Tesla's structural battery pack uses adhesive bonding between cells and the chassis, increasing stiffness by 20% while reducing mass.

Thermal management requirements vary significantly based on pack architecture. Modular designs typically implement cooling at the module level, using aluminum cold plates with liquid glycol coolant. Cell-to-pack systems require more sophisticated approaches, such as Tesla's 4680 pack which uses a dielectric cooling fluid that contacts every cell surface. This design reduces maximum cell temperatures by 15°C compared to traditional cooling plates. Air cooling persists in some applications, particularly LFP chemistries with higher thermal stability, but demonstrates 30% lower heat dissipation capacity than liquid systems.

Voltage and capacity requirements drive fundamental design choices. High-performance EVs targeting 800V systems require careful attention to series cell count and insulation requirements. The Porsche Taycan's 800V pack uses 198 series-connected pouch cells with reinforced isolation barriers between cell groups. Capacity scaling follows different strategies - some manufacturers increase parallel cell count while others opt for larger format cells. CATL's Qilin battery demonstrates the latter approach, using 140Ah cells in a 1024V system that delivers over 600km range from a 100kWh pack.

Innovations in manufacturing complexity reflect these architectural shifts. Cell-to-pack designs reduce part count but require more precise manufacturing tolerances. BYD's blade battery production involves laser welding of cell tabs directly to busbars within millimeter-level precision. Tesla's structural pack demands exact cell alignment during adhesive curing to ensure proper load paths. These methods increase production equipment costs by 25-40% but yield 15-20% improvements in pack energy density.

Case studies from industry leaders reveal distinct design philosophies. Tesla has transitioned from 18650 to 21700 to 4680 cell formats across generations, each change improving energy density and manufacturability. Their latest structural pack achieves 400Wh/L through tabless cell design and integrated cooling. BYD's blade battery prioritizes safety and cost, using LFP chemistry in a pack that passes nail penetration tests without thermal runaway. LG Energy Solution's pouch cell-based designs favor energy density, with their latest products reaching 250Wh/kg in Hyundai's E-GMP platform.

Cooling system innovations continue to advance pack capabilities. BMW's fifth-generation packs use refrigerant-cooled aluminum plates with precise temperature control to ±2°C across all cells. This maintains optimal performance while enabling 195kW fast charging. NIO's 150kWh semi-solid state pack employs passive thermal management, relying on the inherent stability of its chemistry to eliminate liquid cooling hardware.

Safety systems have evolved in parallel with pack architectures. Modern designs incorporate multiple protection layers including cell-level fuses, module-level contactors, and pack-level pyro-fuses. Thermal runaway propagation prevention uses ceramic insulators and fire-resistant materials between cells. CATL's latest packs can contain single-cell failures without propagation for over 5 minutes, meeting stringent new safety standards.

The future of EV battery pack design points toward further integration and material optimization. Cell-to-chassis architectures will likely dominate premium segments, while cost-sensitive applications may adopt simplified cell-to-pack designs. Ongoing developments in solid-state batteries could revolutionize pack architecture by eliminating liquid electrolytes and enabling even denser configurations. However, these advances must balance against manufacturing scalability and cost targets that remain critical for mass market adoption.

Each design approach involves careful tradeoffs between performance, cost, and reliability. The industry continues to explore new configurations that push the boundaries of energy density while meeting stringent safety requirements. As battery technologies evolve, so too will the packaging strategies that make electric vehicles increasingly competitive with conventional transportation solutions.