A Method for SOH Estimation of Lithium-ion Battery Based on Partial Constant-current Charging Voltage Curve

Lithium-ion battery is widely used because of its advantages, such as large energy density and the long life. The accurate estimation of the state of health(SOH) of the lithium-ion battery is beneficial to the rational use of the lithium-ion battery. For the situation that the complete charging process of lithium-ion battery is rare and the discharge process is irregular due to different working conditions, a method for the state of health estimation of the lithium battery based on a partial constant-current charging voltage-time curve was proposed. In this method, the state of health of the lithium battery was defined by the energy between the two voltage points of the charging curve.The two voltage characteristic points are determined by the state of charge(SOC) corresponding to the two voltage points and the relative error between the estimated value of the SOH and the measures value of the SOH.Because of the effect of cycle aging on the state of health, the cyclic coefficient was introduced to reduce the relative error between the estimated value of the SOH and the measured value of the SOH. The results showed that the maximum relative error of the SOH was less than +/- 3% by the method proposed in this paper. This method has a high accuracy and can provide a reference for on-line estimation of the SOH.