A production battery pack for an EV is not a single device but a layered assembly — cells grouped in series and parallel, organised into modules, managed by a Battery Management System (BMS), wrapped in a structural polymer or metal shell, and finally validated on an end-of-line (EOL) tester [S1][S2].
Mathworks' published Simscape Electrical reference model uses three series-connected modules containing a total of 130 cells, with Module A and B each built as 20-series / 2-parallel and Module C as 25-series / 2-parallel, illustrating the dominant automotive pack architecture [S1]. Form factor choice is the first engineering fork: pouch, can, compact cylindrical, or regular cylindrical [S1].
Cell Form Factor and Module Topology Choices
Cell form factor is the first hard spec on the production BOM: the same pack nominal voltage and capacity can be built from four physically different cells, and the cell choice cascades into laser-welding versus ultrasonic-bonding joining processes, thermal-interface material (TIM) selection, and compression-frame design [S1]. Pouch cells in the reference example use the Battery (Table-Based) Simscape block, with cell capacity varying cell-to-cell by a defined Ahr tolerance — the model explicitly parameterises "manufacturing tolerances or uncertainties" on the single-cell Ahr rating [S1].
Module topology is described as a simple two-axis decision: number of cells in series (sets module voltage) and number of cells in parallel (sets module Ah and redundancy). The 20s2p versus 25s2p split in the reference pack is a common automotive pattern: 20–25 cells in series per module keeps each module in the 60–100 V DC band, which simplifies contactor, fusing, and service-disconnect rating downstream [S1]. Custom battery pack builders such as Rose Batteries and Alexander Technologies publish design-to-build services around these series-parallel matrices rather than selling fixed SKUs, reflecting the project nature of industrial and aviation packs [S3][S4].
Pack-Level Assembly Sequence and Joining Processes
The mechanical pack line typically runs cell-stack preparation → busbar and tab joining → module housing closure → module-to-pack series wiring → BMS/contactors/CAN harness → thermal-loop pre-fill → enclosure fit-out → EOL test. The referenced shell-process note frames the pack housing itself as a multi-step polymer or composite flow: raw material procurement of high-grade polymer, pre-treatment (cleaning/drying), forming, and integration with internal mounts [S2]. Shell integrity matters because a single pack enclosure has to hold cell compression loads, route coolant, and meet IP rating and drop-test requirements simultaneously [S2].
Joining is dominated by laser welding of aluminum or copper busbars and tabs for pouch/cylindrical cells, with ultrasonic wire bonding common on cylindrical cell-top contacts. Coolant manifolds are typically integrated at the module level, with the module block exposing FlwR (coolant flow rate) and FlwT (inlet temperature) ports in the simulation reference, and Amb (ambient) for thermal boundary — a hint that the thermal-management loop is designed in parallel with the electrical series-parallel map, not after it [S1].
Battery Management System and Control Integration
The pack's BMS is the system that turns a stack of electrochemical cells into a controllable, certifiable product. The Mathworks Controls subsystem defines charging current as a function of cell SOC, cell temperature, and the maximum C-rate allowable at that temperature, illustrating the canonical BMS input set [S1].
Two output ports per module — SOC and Temp — feed the central pack controller, while electrical pos/neg ports carry the high-current path. The auxiliary load (chiller, cooler, EV accessories) is modelled separately from the pack, which is consistent with a real production split between the HV battery loop and the 12/48 V accessory network [S1]. At the remanufacturing and warranty stage, dedicated battery control unit (BCU) testers are used to validate BMS behaviour against the original test specification, indicating that the BMS test code is preserved as a long-lived artefact across the product lifecycle [S5].
End-of-Line Test, EOL Coverage and Quality Stack
EOL test for a battery pack is unusually broad because three independent failure modes must be exercised on every unit leaving the line: electrical performance (capacity, internal resistance, OCV), BMS functional (cell balancing, SOC estimation, contactor sequencing, fault injection), and safety/thermal (insulation resistance, hipot, leak, thermal-runaway containment). DMC's published BCU tester case study notes that client engineers selected the instrumentation, designed the hardware platform for the battery module test station, and developed the test specifications — a workflow that points to a test spec authored by the pack maker, not generic vendor defaults [S5].
Cell Ahr variation, modelled as a parameter, is not just a simulation concern: it defines the worst-case balancing time the BMS must support, and therefore the maximum cell count that can be put in parallel without extending formation cycling. Quality-management is structured against ISO 9001 and, where automotive customers demand it, IATF 16949 and VDA 6.3 process audits, with the related CPU Manufacturing Quality Standards: ISO 9001, JEDEC and OEM Audit Stack piece mapping the audit stack across both battery and semiconductor cell-level manufacturing.
Capacity Planning, Cost Stack and Sourcing Logic
Pack-level cost is dominated by the cells (typically the majority of pack BoM cost), the BMS electronics, the thermal loop, and the enclosure. The 2026 spec bands for hydroxide, cell, and pack capacity are tracked separately from the cost stack, and an OEM/ODM sourcing lens is the right tool for buyers trying to separate cell IP from pack-assembly IP — see the Lithium OEM vs ODM Manufacturing: 2026 Spec Bands, Certifications and Sourcing Logic and Lithium Production Capacity Planning: 2026 Cell, Pack and Hydroxide Spec Bands references. [S1]
For QA and supplier tier signals, the Lithium Battery QA Stack 2026: Standards, Cell Testing and Supplier Tier Signals note covers cell-level testing depth, while the cobalt refining line items in Cobalt Manufacturing Cost Breakdown: Mining, Refining, Cathode-Active Line Items explain why cathode chemistry choices still drive pack energy density and therefore module topology. For trade-flow context on the upstream cell side, China Lithium Battery Export Flow Hits Multi-Year High, Trade Mix Reshapes tracks the export channel that most non-Chinese pack makers ultimately source from.
Who Pack Manufacturing Is For, and Where It Fails
Pack manufacturing is for: automotive Tier-1s building differentiated products on shared cell platforms; specialty integrators serving aviation, UAV, AGV/robotics, and e-mobility niches; and OEM/ODM projects that need a custom form factor with a defined BMS interface [S3][S4]. It is not for buyers expecting a fixed catalogue SKU with stock-level lead times — the reference service pages explicitly market design-to-build, not off-the-shelf delivery [S3][S4].
Common failure modes at the pack level trace back to: (1) underestimated cell-to-cell Ahr spread causing long balancing tails; (2) thermal-loop flow maldistribution across parallel strings; (3) BMS test coverage gaps that only surface at remanufacturing [S1][S5]. The 2-RC equivalent-circuit model used in the Mathworks reference — a standard engineering abstraction for lithium cells — assumes no capacity fade and no charge leakage, which is appropriate for production-line simulation but not for warranty prediction, and any team using it for lifecycle claims should switch to an ageing-aware model [S1].
Engineering-Process Links to Adjacent Plant Equipment
Pack plants overlap with adjacent industrial equipment lines on three points: structural shell manufacturing (compression molding, V-process lines for enclosure blanks), inline metrology for cell dimensional control, and high-reliability process instrumentation for the formation and aging cyclers. The V-process molding line is one of the established methods for shell blanks at scale, and supplier mapping for that equipment family is documented in V-Process Molding Line Suppliers: China Cluster Map and Quoted Bands. On the digital-factory side, Industry 4.0 in Lithium: IIoT, AI and Flexible Production Architecture lays out the data spine most modern pack lines are being spec'd against. [S2]
Track the next signals on three nodes: (1) expansion announcements tied to 20s2p and 25s2p module architectures in the EU and US cell-gigafactory pipeline; (2) revisions to BMS functional-safety test specs as ISO 26262 work products are re-issued; (3) any packaging-format shifts from pouch to large cylindrical or prismatic that would force busbar-joining line retooling.
For component-level specifications, see additive manufacturing material, multifunction process calibrator, and v process line.