A golf cart battery pack’s discharge capacity measured in a single-unit test is often treated as a fixed cell property, but this study shows that assumption has clear limits. The same pack can yield very different capacities depending on whether its Battery Management System (BMS) heating logic is actually triggered during the test. Using six packs evaluated through both certified-laboratory and in-house testing, we demonstrate that BMS logic activation—not the cell alone—often determines the measured result, so a single test cannot be trusted on its own for pack selection. Six battery packs (Pack A–F) covering the main cell chemistries and form factors used in golf cart powertrains were compared. High-load certified tests (1C/2C/3C) at two independent ISO/IEC 17025 laboratories were combined with low-load in-house tests (0.5C) approximating real golf cart operation. The core experiment used Pack D: on the same specimen, capacity was measured with its low-temperature heating logic not triggered and again when triggered, with all other conditions identical. Pack B was re-tested after eight months at a second laboratory to observe how the result shifts with elapsed time and testing site. For Pack D, the same specimen produced 36.84 Ah when the heating logic was not triggered versus 99.497 Ah when it was—a 2.7-fold difference at -10℃ attributable mainly to whether the BMS heating logic actually operated. The two conditions differed in BMS firmware version (presence of the heater-relay logic), so this comparison isolates the design axis rather than the test-protocol axis. Consistent with this, at -10℃/3C Pack A recorded only 4.49 Ah, a collapse driven by BMS cut-off rather than the cell itself. The eight-month Pack B re-test added two secondary effects: capacity declined by -15.7% at -10℃/3C(250A) and -25.8% at 45℃/3C(250A). Pack F, a repurposed (second-life) pack, performed at or above its rating across most conditions, contradicting the assumption that second-life batteries are weak at low temperature and high load. A measured discharge capacity is not a fixed property of the cell alone; it is a joint function of the pack's BMS design (firmware) and the test protocol (soaking, external power, trigger conditions). Pack D demonstrates the design axis: the same specimen yielded 36.84 Ah or 99.497 Ah at -10℃ depending on whether the heater-relay logic was present in the firmware. The protocol axis was not tested in this study and remains a limitation. Combining certified-laboratory and in-house testing makes it possible to verify whether the BMS logic actually operated and to expose pack-specific operating limits that a single test would miss.

1. 연구 배경 및 목표
    1.1 연구 배경
    1.2 문제 제기 — 단품 평가의 한계
    1.3 연구 목적 및 기여
2. 관련 문헌 연구
    2.1 리튬이온 배터리 팩 신뢰성 평가
    2.2 팩 BMS 설계와 지표 타당성
    2.3 공인시험 다원화와 확장 검증
3. 시험 방법
    3.1 6종 배터리 팩 사양
    3.2 BMS 핵심 보호 및 기능 로직 비교
    3.3 공인 및 사내시험 이중 검증 설계
    3.4 Pack B 재측정 검증 설계
    3.5 Pack D BMS Heating 로직 활성화 조건 통제실험
4. 실험 및 결과
    4.1 6종 단품 시험 결과
    4.2 Pack D 설계(펌웨어) 축 의존성 — 주요 관찰
    4.3 Pack B 재측정 노화 정량화
    4.4 Pack F 용도 전환(repurposed) 배터리 재평가
    4.5 통합 해석 — 단품 평가의 3가지 구조적 한계
5. 결론 및 향후 연구
Acknowledgement
References

• Young-Chan Yoon(Department of Industrial and Information Systems Engineering, Jeonbuk National University, Reliability Section, R&D Team 1, DY Co., Ltd.) | 윤영찬 (전북대학교 산업정보시스템공학과, 디와이㈜ 연구개발1팀 신뢰성담당)
• Ki-Seok Song(Reliability Section, R&D Team 1, DY Co., Ltd.) | 송기석 (디와이㈜ 연구개발1팀 신뢰성담당)
• Jang-Hyun Baek(Department of Industrial and Information Systems Engineering, Jeonbuk National University) | 백장현 (전북대학교 산업정보시스템공학과) Corresponding author