Thermal Response of LiFePO4 Pouch Cells Under Dynamic Drive Cycles: Effects of Ambient Temperature and Battery Pack Size

Low-power electric vehicles are expanding rapidly in India, where ambient temperatures of 35–40 °C are common, yet experimental data on large-format LiFePO4 (LFP) cells under realistic drive-cycle loading in such climates are scarce. A 20 Ah LFP pouch cell was loaded with cell-level power profiles derived from the IUDC, WLTC Class 1 and WLTC Class 2 cycles for packs of 16–80 cells (≈1–5 kWh) at ambient temperatures of 25–40 °C, under natural convection and forced air at 3 m/s. The results were assessed against a thermal-management target (≤35 °C and surface temperature difference ≤5 °C) and the manufacturer’s upper operating limit (55 °C). Under natural convection, the temperature rise above ambient fell from 11.5–17.5 °C for the 1 kWh pack to ≤4.5 °C for the 4 and 5 kWh packs, consistent with the inverse scaling of cell current with cell count. The target was met under all cycles only by the 4 and 5 kWh packs at ≤30 °C; at 35–40 °C, no ambient-air strategy can meet it. At 40 °C, the 1 kWh pack reached 55.3–57.5 °C under WLTC loading. Forced air reduced the temperature rise by 28–41% at 25 °C but by only 4–20% at 40 °C; it kept the 2 kWh pack at least 7.9 °C below the limit, but not the 1 kWh pack under WLTC Class 2 at 40 °C. The resulting operating envelope supports pack sizing and thermal management of low-power electric vehicles in hot climates.