리튬이온전지 Cell Balancing에 관한 연구

Abstract

This study was conducted to improve the cell balancing performance of a battery management system (BMS) for stable use of lithium-ion batteries. The cell balancing of the BMS takes too much time because the balancing current cannot be increased during the repeated charging/discharging and stabilization operations of lithium-ion batteries. When the BMS bears the current above the specification, the long-term failure and burnout of components can occur due to persistent heat-generation with concerns about a risk of fire if it fails to respond immediately. The proposed BMS in this thesis aimed to secure stability and increase the speed of balancing by minimizing the heat problem occurring in the cell balancing through passive balancing, which reduces the delay time to reach the nominal voltage from the abnormal voltage in the event of overcharging or overdischarge. Furthermore, the overall resistance was lowered and the heat applied to the load was also reduced to minimize the heat problem by connecting additional resistors in parallel through comparing and analyzing the cell balancing performance of the BMS based on the experimental results, and the excess voltage was divided into several resistors for higher durability. This thesis can be presented as important data on the design and fabrication criteria of the circuits applying the passive balancing with respect to the heat problem during cell balancing in the BMS.| 기존의 BMS는 리튬이온 전지의 충방전과 안정화 작업 반복 과정에서 Balancing 전류를 크게 할 수 없어 Balancing의 시간이 길고, BMS의 내장된 스펙 이상의 전류량을 감당하게 될 경우, 지속된 발열로 장기적으로 부품의 고장 및 소손이 발생하며, 빠르게 대처하지 못할 시 화재의 발생이 우려된다. 따라서 본 논문에서는 개선된 전지 모듈 간 Passive Balancing을 통해 기존의 Balancing 도중 발생하는 고질적인 문제인 발열 문제를 개선하여 안정성 확보와 Balancing의 속도를 높임으로 과충전, 과방전 발생시 이상전압 상태에서 공칭전압으로 도달하기 위한 시간 지연을 단축시켜 전지의 손상을 최소화하는 회로를 제안하며 실험을 통하여 제안한 회로의 타당성을 입증하고자 한다.