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Electric vehicle (EV) battery architecture is more than just a collection of cells. It’s a sophisticated system engineered for safety, efficiency, and longevity. At Munro & Associates, teardown analysis provides a detailed lens through which we decode these complex systems. A detailed breakdown of EV battery construction reveals the journey from the smallest cylindrical cells to the massive structural packs that power vehicles like the Tesla Model Y and Hummer EV. This deep dive offers insight into how expert engineering choices affect performance, safety, and cost.
Understanding EV Battery Cell Formats
The three main battery cell formats—cylindrical, pouch, and prismatic—each have unique mechanical and thermal characteristics. Cylindrical cells, such as the 18650, 2170, and Tesla’s tabless 4680, are commonly used due to their mechanical robustness and ease of manufacturing. The tabless design of the 4680, for instance, reduces internal resistance and improves heat dissipation, allowing more efficient current flow and reducing hotspot formation.
Pouch cells, on the other hand, offer excellent volumetric efficiency but demand compression management due to their tendency to swell during charge/discharge cycles. Prismatic cells combine the best of both—rigid outer shells like cylindrical cells and efficient space use like pouches—though they still require compression systems to manage expansion.
Module Assembly and Electrical Configuration
At the next level up from individual cells are battery modules, which combine series and parallel cell groupings to form higher-capacity, higher-voltage units. Cells connected in parallel form “cell groups” that behave as a single cell with higher current capacity. Modules then connect these groups in series to raise the voltage. This architecture is expressed in formats like 12S72P, meaning 12 cell groups in series, each with 72 cells in parallel.
Module design plays a critical role in overall pack efficiency. For example, Lucid Air’s modules use wide and narrow bond wires to function both as current paths and fuses. Tesla’s latest designs move away from fragile bond wires, opting instead for laser-welded current collectors that enhance reliability and current handling.
Cooling Strategies and Thermal Management
Thermal management is critical in EV battery design. Cylindrical cells are often cooled from the side or the bottom. Early Tesla modules used simple straight-line coolant channels, but newer designs evolved into serpentine layouts that enhance heat exchange by maximizing contact with cell surfaces.
Tesla’s Plaid modules introduced a split serpentine channel with both inlet and outlet on the same end. This allows coolant to flow down one path and back another, equalizing temperature across all cells—improving cell longevity and overall pack efficiency.
Pouch cells, like those in the Hyundai Ioniq 5, present cooling challenges due to their flat shape and dynamic swelling. While early approaches used aluminum plates with integrated coolant channels, cost-driven designs today rely on thermally conductive adhesives and foam springs to manage heat and expansion.
Cell-to-Pack vs. Module-Based Design
Traditional battery packs follow a cell-to-module-to-pack (CTMTP) architecture. However, recent designs such as Tesla’s 4680 structural pack use a cell-to-pack (CTP) architecture, removing the module level entirely. While this increases energy density and reduces cost, it sacrifices repairability—making these packs effectively disposable if damaged.
Structural packs also require advanced thermal and mechanical integration. The Tesla 4680’s side-cooled design—enabled by the tabless architecture—shows how removing traditional bottlenecks like tabs opens new pathways for heat to escape, helping maintain cell health even under heavy loads.
Battery Management Systems (BMS)
Battery Management Systems ensure safety, efficiency, and longevity by monitoring voltage, temperature, and charge state across cell groups. A well-designed BMS balances cells passively—using resistors to bleed excess charge—or actively—transferring energy from higher-charged cells to lower-charged ones.
Tesla uses localized BMS satellites for each module, reducing the need for “spaghetti wiring” and minimizing the risk of vibration-induced failures. In contrast, centralized BMS systems require more complex wiring but may simplify logic and cost. Regardless of design, BMS plays a pivotal role in preventing overcharge, over-discharge, and thermal runaway.
Real-World Applications: From Rivian to the Hummer EV
The teardown walks through real-world examples, from Rivian’s 2170-based modules to GM’s reconfigurable Hummer EV pack. Rivian uses 72P12S modules for energy scalability, while GM’s Hummer dynamically reconfigures its pack from 96S6P (400V) to 192S3P (800V) for faster DC charging—an advanced example of adaptive battery architecture.
Other notable examples include:
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Lucid Air: Wide/narrow wire fusing, bottom-cooled cylindrical cells, and thermal interface material optimization.
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Hyundai Ioniq 5: Large pouch cells, bottom-cooled via TIM and simplified mechanical integration.
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Chevy Bolt: Evolution from complex aluminum cooling plates to cost-optimized adhesive TIM cooling.
Each design reflects a trade-off between cost, performance, repairability, and safety.
Energy vs. Power: The Importance of C-Rate
Amp-hours (Ah) define a cell’s energy capacity—how long it can deliver a set current. Multiply this by nominal voltage, and you get watt-hours (Wh), a measure of stored energy. But energy is not the same as power.
Power is energy per unit time and is defined by C-rate. A 1C discharge of a 5Ah cell delivers 5A; 2C delivers 10A. High C-rates deliver better performance but demand superior cooling and stress-tolerant materials. While this session focused on energy, future teardown content will dive into power ratings and C-rates—critical concepts for drivetrain engineers and EV investors alike.
Usable Energy and Over-the-Air Adjustments
The energy advertised by manufacturers is often “usable energy”—a subset of total (gross) capacity. Buffer zones at the top and bottom of the charge range protect battery longevity. OEMs may dynamically adjust usable energy through software updates, whether for range extension during emergencies or paid unlocks for additional capacity.
This distinction is critical when comparing EVs: A pack rated at 100 kWh may only deliver 95–96 kWh to the driver depending on configuration and BMS tuning.
Conclusion: Why Architecture Matters
From cell format to cooling strategy, every decision in EV battery architecture impacts performance, cost, serviceability, and longevity. Munro & Associates’ teardown insights illuminate the engineering choices behind industry-leading vehicles, offering OEMs and suppliers data-backed recommendations for lean, high-performance battery design.
Whether you’re developing next-gen modules, assessing investment risks, or simply fascinated by electric propulsion, understanding the structure—from cells to packs—is essential.
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