State of health estimation of retired battery for echelon utilization based on charging curve

Recently, the number of retired batteries for electric vehicles is gradually increasing with the improvement of the market share of electric vehicles. The demand for echelon utilization of retired batteries has become increasingly prominent. For the echelon utilization of retired batteries, compared with fresh batteries, more accurate state of health (SOH) estimation methods are needed to ensure the safe operation of the energy storage system. Taking the retired battery as the research object, this paper further carries on the accelerated aging test on the retired battery under the condition of variable environment temperature. Based on the voltage change in the constant current charging stage and the current change in the constant voltage charging stage, feature parameters that can reflect the dynamic change of the battery charging curve are extracted to estimate the battery discharge capacity. This paper also extracts feature parameters that can reflect the change of environment temperature and battery aging condition through correlation analysis. Finally, the SVR model is used to estimate the capacity of the retired battery. The selected feature parameters are used as input, and the battery discharge capacity is used as output. The accuracy of the model is verified with experimental data.