Study on actual Ah‐throughput‐based health indicator of battery module consisting of inconsistent cells for its second life

In this Letter, an actual Ah‐throughput‐based novel health indicator (HI) of battery module is proposed for its second life. The state of health (SOH) of a battery cell is generally evaluated by the cell capacity. However, it is difficult to define the SOH of a battery module since it consists of inconsistently aged cells. To represent module aging and the inconsistency, this Letter utilizes the actual Ah‐throughput, which is the total amount of current suppliable to a load, as the module HI. Ah‐throughput is affected by loss from cell balancing control, which is necessary for the safe and efficient operation of a battery system. The larger the inconsistency, the more balancing operation is needed. Therefore, the proposed HI can evaluate the module health reflecting the inconsistency from a balancing perspective. For the implementation of the HI, its derivation and calculation algorithm are presented. Finally, the effectiveness is verified by various case studies with an experimental setup consisting of a series‐connected cells and an active cell balancer.