Performance Evaluation of High-Energy LiFePO4 Battery Pack for Electric Shuttle

Abstract

Abstract For tourism-based electric shuttles, high-energy batteries are crucial. A 200 Ah Lithium Iron Phosphate (LiFePO4) battery pack has been designed yet lacks performance evaluation. We conducted performance tests based on ISO 12405-4:2018. The battery comprises 24 cells connected in series, resulting in a 72 V output voltage. Under controlled conditions at 23°C, the test assessed charging and discharging at defined C-rates. The study assessed the resistance, capacity, and efficiency. We also monitored heat distribution in the battery system during test to detect abnormalities. The results revealed that the maximum attainable battery charge rate was C/3. Under this rate, the discharge capacity reached 160 Ah, and the battery temperature rose to just below 36.2°C. On the other hand, charging the battery at C/6 yielded 191.5 Ah, which increased the battery temperature to 31°C. Thus, the energy round-trip efficiency was measured at 86.5%. However, charging the battery at C/3 led to the Battery Management System (BMS) overheating, indicated by the casing temperature exceeding 67 °C. The overheating caused severe damage to the BMS charging component and triggered an automatic cut-off. The higher total battery resistance during charging was identified as the root cause of the issue, emphasizing the need for future research to focus on enhancing the BMS for faster and more efficient charging, improving the service reliability of the electric shuttle.