電動車電池系統可靠度與維護度相關問題探討

Abstract

隨著全球永續環保意識的抬頭，世界各國使用電動車(Battery Electric Vehicle, BEV)之比例逐年增加，電動車的使用壽命與可靠性也被受關注。而電動車發展至今為了讓使用者有更好的體驗，各家廠商也推出了不同充電速度之充電設備供使用者選擇，但不同的充電速度對於電動車電池之退化也會有所影響。除此之外，隨著電動車投入市場已超過10年，需要更換電池的電動車也逐漸增加，但目前為止還沒有相關針對更換電動車電池，對其電池系統可靠度與壽命影響的研究。本研究旨在以可靠度工程之方法分析與探討電動車電池系統的相關問題，根據慕尼黑工業大學之電池性能衰退數據，使用可靠度方法分析不同充電電流下之電池、電池模組與電池組之可靠度與平均失效時間，並探討以串聯或並聯系統之失效模型來分析電動車電池系統可靠度之影響差異，以使研究結果盡可能的貼近實際使用情況，此外將加入探討使用不同電流充電之電動車，在不同時機更換不同數量之電池模組，對其可靠度與平均失效時間的影響。研究結果顯示，電動車電池系統以串聯系統分析時，1 A充電的平均失效時間為2 A充電的2.3倍，以並聯系統分析時，1 A充電的平均失效時間為2 A充電的3.6倍，意旨較慢之充電速度，對於電動車之電池平均使用壽命有著較好的表現，並且在並聯系統中更為顯著。而在若有一個電池模組失效便判定電動車電池系統失效之串聯系統失效模型下，在維修更換電池模組時，若只更換部分數量之模組對電池系統可靠度並無明顯效果，且在不同時間更換也無明顯之差異，但相較起來使用較慢速之1 A充電電流充電之電動車，更換電池模組對其可靠度有較好的改善效果，其在更換8個電池模組後，可增加約5 %之平均失效時間。

The growing adoption of battery electric vehicles (BEVs) has raised concerns about battery lifespan and degradation. Manufacturers offer various charging speeds, affecting battery performance and longevity. As BEVs have been in use for over a decade, battery replacements due to capacity loss are becoming more common. However, limited research exists on how battery replacements impact reliability and lifespan. This study employs reliability engineering methodologies to analyze BEV battery system reliability. Using battery degradation data from the Technical University of Munich, reliability analysis is conducted to evaluate the mean time to failure (MTTF) of individual battery cells, battery modules, and battery packs under different charging currents. Additionally, the study examines the effects of series and parallel failure models on BEV battery system reliability, ensuring that the findings closely reflect real-world conditions. Furthermore, it investigates how replacing different numbers of battery modules at varying intervals influences system reliability and MTTF in BEVs utilizing different charging currents. Results show that in a series-connected system, MTTF for 1A charging is 2.3 times that of 2A charging. Under 1A charging, a parallel-connected system has twice the MTTF of a series-connected one, highlighting that slower charging extends battery lifespan. Additionally, in current electric vehicle battery systems, partial replacement of battery modules does not yield a significant improvement in system reliability, regardless of the replacement timing. However, at 1A charging, reliability improves more noticeably after module replacement, with replacing eight modules increasing MTTF by approximately 5%.