Incremental Capacity Analysis Applied on Electric Vehicles for Battery State-of-Health Estimation

The state of health (SoH) of electric vehicle (EV) batteries is important for the EV owner and potential buyer of second hand EVs. The incremental capacity analysis (ICA) has by several researchers proven to be a promising SoH estimation method for lithium-ion batteries. However, in order to be practical useable, the method needs to be feasible on a pack or EV level and not only on an individual cell level. Therefore, the purpose of this article is to demonstrate the feasibility of the ICA method on real EVs. Nickel manganese cobalt (NMC) cells used in BMW i3 EVs and lithium manganese oxide (LMO) used in Nissan Leaf EVs have been tested both on the cell level and on car level. The results are consistent and the characteristic peaks and valleys of the ICA on car level match with the same on cell level. A root-mean-square error of 1.33% and 2.92% has been obtained for the SoH estimation of the NMC and LMO type, respectively. It is therefore concluded that the ICA method is also applicable to the car level for battery SoH estimation.