Project 04
Mechanical design of FalconE Racing’s pouch-cell accumulator: segment packaging, aluminium containment, impact-load analysis, chassis mounting and cooling provisions for a Formula Student EV.
Project overview
The accumulator mechanical design brings 144 pouch cells into a compact, segmented high-voltage pack. The work covers a lighter aluminium enclosure, cell restraint and fire barriers, Formula Student impact-load calculations and structural simulations, mounting interfaces, and preliminary cooling design. Figures and values below are design calculations and simulated results, not physical test certification.
01 / Architecture
Replaced 72 Enepaq Energus modules (46.224 kg) with 144 × 14 Ah pouch cells (40.032 kg in the mass comparison), saving 6.192 kg at cell/module level. Used a conservative estimated accumulator mass of 72 kg for structural loading, down from a 78 kg steel-walled predecessor; the new casing uses aluminium walls and base, so the estimate retains margin rather than claiming a measured final mass. Packaged the cells in 24-cell segments with monitoring PCBs, connectors and fasteners; the pack envelope shown in the design is 615.77 × 414.00 × 268.01 mm.
Developed the enclosure, removable lid, segment partitioning and battery-to-chassis packaging as a coordinated mechanical assembly.
| Design measure | Baseline / input | Pack design |
|---|---|---|
| Cell/module mass | 72 modules · 46.224 kg | 144 pouch cells · 40.032 kg |
| Estimated accumulator mass | 78 kg steel-walled | 72 kg conservative structural input |
| Pack envelope | — | 615.77 × 414.00 × 268.01 mm |
Table 01-01 — Mass comparison, conservative load assumption and CAD envelope from the design document.
02 / Vehicle integration
03 / Structural validation
Applied FSUK 2025 T9.2 critical-component accelerations: 40g forward/rearward and left/right, and 20g up/down. At the conservative 72 kg design mass these correspond to 28,252.8 N and 14,126.4 N. Analysed the aluminium 6061-T6 casing and brackets across all six directions. Minimum simulated safety factors were 1.15 (right), 1.06 (left), 1.205 (forward), 1.304 (rearward/up) and 1.637 (down). Checked a 24-cell segment at 20g vertical acceleration using 7.168 kg dynamic mass (24 × 282 g cells plus 400 g PCB/connectors/fasteners): 1,406.36 N total and about 351.59 N per fastener, assuming four equal load paths.
Selected M8 grade 8.8 segment bolts; calculated single-shear bolt stress of ~7 MPa and 3 mm aluminium segment-casing bearing/shear estimate of 4.65 MPa. The segment simulation returned a minimum safety factor of 1.6697.
| Casing load case | Minimum simulated safety factor |
|---|---|
| 40g right | 1.15 |
| 40g left | 1.06 |
| 40g forward | 1.205 |
| 40g rearward | 1.304 |
| 20g upward | 1.304 |
| 20g downward | 1.637 |
Table 03-01 — Minimum safety factors reported for the aluminium 6061-T6 casing and brackets in the design analysis.
04 / Mounting
Distributed the 72 kg accumulator load across eight mounting bolts in the hand calculation: 3,531.6 N shear per bolt at 40g and 1,765.8 N tension per bolt at 20g. Selected M10 grade 8.8 mounting bolts; calculated ~44.97 MPa single-shear stress per bolt against a 320 MPa assumed allowable (640 MPa yield / factor of 2). Calculated ~46.84 MPa bracket shear in 6 mm aluminium 6061-T6 against a 155 MPa assumed allowable (310 MPa yield / factor of 2). Structural load paths were also investigated by simulation.
05 / Thermal protection
Enclosed pouch-cell tops and sides with 3 mm UL94-V0-rated, electrically insulating FR4 sheets, allowing only paired cell tabs through narrow slots; additional FR4 separates adjacent segments and caps each segment. Separated segments with 3 mm aluminium walls extending to the accumulator lid. Openings occupying about 7% of each wall expose tabs and cell-monitoring PCBs to an air channel exhausted by low-voltage-powered server fans.
The preliminary thermal worksheet uses a 600 V pack, 80 kW maximum draw, 133.33 A pack current and 35.56 W heat generation per cell, yielding a 5,120 W full-pack heat-load estimate. These are sizing assumptions, not measured rejection. The same worksheet separately explores aluminium-plate/water-cooling calculations: a 1.74 °C cell-to-water temperature difference and 0.70 kg/s required coolant flow at a separate 1.74 °C coolant temperature rise for 5,120 W. This is an explored estimate, not evidence that the pictured air-cooled layout incorporates a water circuit.
| Sizing input | Worksheet value |
|---|---|
| Pack voltage / peak power | 600 V / 80 kW |
| Peak pack current | 133.33 A |
| Estimated heat per cell | 35.56 W |
| Estimated pack heat load | 5,120 W |
| Water-loop study (separate calculation) | 0.70 kg/s at 1.74 °C coolant rise |
Table 05-01 — Preliminary thermal sizing calculations; the forced-air layout and water-loop worksheet are distinct concepts.