Active cell balancing algorithm for serially connected li-ion batteries based on power to energy ratio

This paper presents simple but effective cell balancing algorithm for serially connected lithium ion batteries based on the power to energy ratio balance and relative capacity estimation. Compared to simpler balancing algorithm such as voltage based cell balancing that begins balancing after cell imbalance is detected, the proposed algorithm can predict the imbalance between cells due to capacity invariance. Therefore, the proposed balancing algorithm can reduce the amount of time it requires to balance the cell. Comparing to a more advanced algorithm such as remaining charge estimation algorithm, the system proposed in this paper uses the simple PI control to estimate relative capacity thus reducing the computational complexity. In this paper, in order to demonstrate the proposed balancing algorithm flyback type equalizer is used as balancing circuits and both cell-to-pack (C2P) and pack-to-cell (P2C) methods are discussed. The experimental results are presented as balancing algorithm performance verification.