Design methodology for passive balancing circuit including real battery operating conditions

The passive balancing (PB) circuits are still the most common solution for the voltage equalization of series-connected battery cells due to the higher reliability, lower cost and control simplicity compared to the active balancing (AB) ones. PB circuits are usually designed considering a desired equalization time and constraints on size and power dissipation of the equalization resistors. However, the performance of the PB circuits strongly depend on the battery cells technology as well as the voltage imbalance condition between the most charged cell and the least charged one of a series-connected battery pack. Therefore, additional parameters need to be considered for optimizing the design of the PB circuits. This paper presents a systematic approach for the design of PB circuits for lithium-ion battery packs that takes into account for real cells operating conditions. An extensive numerical analysis is reported to demonstrate the validity of the proposed methodology.