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Tesla’s transition from the 2170 cylindrical cell to the larger 4680 cell represents more than a change in format — it marks a revolutionary shift in electric vehicle (EV) battery architecture, manufacturing strategy, and structural design. In this article, we’ll explore the technical differences between the 4680 and 2170 battery packs used in the Tesla Model Y, drawing from Munro & Associates’ teardown analysis and benchmarking insights. For automotive engineers, EV enthusiasts, and investors, understanding this evolution is key to grasping the future of lean manufacturing and cost-efficient EV engineering.
Understanding the Basics: What Are 2170 and 4680 Cells?
The numbers “2170” and “4680” refer to the dimensions of the cylindrical battery cells: 21 mm in diameter by 70 mm in length for the 2170, and 46 mm by 80 mm for the 4680. While the 2170 cell has powered various Tesla models since 2020, the newer 4680 cell made its debut in the 2022 Model Y. Despite its larger size, the 4680 pack delivers slightly less overall energy capacity—about 67 kWh versus the 2170’s 75 kWh—yet offers strategic advantages in cost, integration, and vehicle structure.
Tesla’s Shift Toward Vertical Integration
The 2170 cells are supplied by Panasonic, whereas the 4680 cells are developed and manufactured in-house by Tesla. This shift toward vertical integration allows Tesla to eliminate supplier markup, which—while modest on a per-cell basis—accumulates rapidly across a pack containing thousands of cells. For instance, the 2170 pack contains over 4,000 cells, while the 4680 pack contains just 828. Manufacturing in-house also gives Tesla tighter control over design, quality, and continuous improvement.
However, building battery cells internally requires significant capital expenditure and technical expertise. Tesla must master both the manufacturing process and the associated quality control — an investment that, if executed successfully, pays off in long-term cost reduction and product differentiation.
Assembly and Structural Simplicity
One of the primary engineering benefits of the 4680 design lies in simplified assembly. Fewer cells mean fewer “pick and place” operations during production, reducing automation complexity and cost. Moreover, fewer cells translate to fewer metal cans per pack, which, in theory, improves gravimetric energy density (the ratio of active material to total mass).
Yet this theory meets a surprising counterpoint in practice. Despite having fewer cells, the 4680 pack includes 56 kg of cell can material—compared to 52 kg in the 2170 pack. Why? The 4680’s can is substantially thicker, a necessity due to its structural integration into the vehicle.
A New Structural Paradigm: The Battery Pack as Frame
The traditional 2170 Model Y battery pack uses a stamped aluminum tray with extrusions and a non-structural silicone-based potting compound for thermal isolation. Each module is anchored with injection-molded rails and compression limiters. This design, while functional, separates the battery mechanically from the vehicle frame.
In contrast, the 4680 pack embodies Tesla’s “structural battery pack” concept. It forgoes conventional modules in favor of “cell arrays” built from bandolier-assembled 4680s adhered to extruded cooling plates. These arrays are dropped directly into a deep-drawn steel tub and held in place with expanding polyurethane foam, creating a rigid, load-bearing structure.
This foam adheres the cell arrays to the battery lid — which doubles as the vehicle’s floor pan. When the lid is riveted in place, it compresses the foam upward, locking the arrays in place and transforming the battery into a structural component. This approach eliminates the need for additional floor support panels and fasteners, streamlining both vehicle weight and production.
Laser-Welded Steel Lids: Cost Meets Customization
The lid of the 4680 pack is a laser-welded blank—an advanced method that allows tailored thickness across different zones of the steel sheet. For example, the front section is thickened for crash absorption, while the midsection is reinforced to support seats and center console mounts. This approach optimizes weight and cost, concentrating material strength where it’s most needed.
Compared to the conventional stamped steel lid of the 2170 pack, the laser-welded lid is an elegant solution for balancing performance with manufacturing efficiency.
Sealing the Deal: NVH and Water Protection
Because the 4680 pack serves as the floor pan, it must provide a complete seal against water intrusion and air leakage. Tesla uses a closed-cell polyurethane seal around the perimeter of the lid to interface with gigacastings and stamped body sections. This sealing strategy is crucial not only for battery protection but also for maintaining cabin integrity.
In contrast, the 2170 pack uses a more traditional extruded rubber seal—effective, but less structurally critical since the vehicle body already contains a complete floor pan.
Witness marks from teardown reveal slight inconsistencies in seal compression around the 4680 pack’s perimeter, hinting at early production quality control challenges. However, improvements are likely as Tesla scales production and incorporates lessons learned into platforms like the Cybertruck.
Vehicle Integration and Interior Impact
Despite structural differences, the 2170 and 4680 packs result in near-identical cabin floor heights. Tesla achieved this by adjusting the Z-axis geometry of the rocker panels and sill sections. The result: even though the 4680 lid is flat and shallow, while the 2170 tray dips down before stepping up at the edges, both packs preserve interior legroom and comfort. Passengers would not notice a difference between vehicles equipped with either battery format.
This harmonization reflects Tesla’s commitment to packaging efficiency and user experience, even while overhauling internal architecture.
Quantifying the Gains: Cost and Mass Savings
Munro & Associates’ benchmarking reveals that the structural 4680 pack delivers a measurable decrease in cost at the pack level. Detailed comparison reports quantify the deltas across subsystems including thermal management, current collectors, foam usage, and modular design elements. The reports also offer CAD-based visualizations and exploded views to help engineers and analysts understand Tesla’s innovative approach.
The mass savings may not be dramatic due to the thicker cans and added structural materials, but the overall reduction in part count, assembly complexity, and supplier reliance contributes to significant efficiency gains.
Final Takeaways: Tesla’s Lean Battery Architecture
Tesla’s shift to 4680 battery cells is not just a matter of form factor — it’s an expression of lean design philosophy applied at the system level. By rethinking the battery pack as a structural element, Tesla has consolidated functions, cut costs, and opened doors to manufacturing scale advantages.
For engineers and investors alike, the 4680 pack offers a glimpse into the next frontier of EV design: where structure, energy storage, and manufacturability converge into a single, optimized unit.
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