Abstract:

 An on-line correction method was proposed for Li-ion battery to reduce the cumulative error from state of charge (SOC) estimation method witch is industrial commonly used. Li-ion battery discharging experiments were carried out with measuring the voltages, currents and temperatures at 0~60 ℃ with discharge rate of 1 C, 2 C, 3 C and 0.33 C to build a Li-ion battery discharge database. Open-circuit voltages were obtained using this database under SOC of 20% and 80% at the same arrange of discharge temperatures and discharge rates mentioned above to determine a straight line of SOC and open-circuit voltage. The SOC corresponding a voltage point on the straight line and a correction factor α were used to correct the SOC obtained by the current integration method. The results show that the error between estimation SOC and actual SOC is less than 4%, which meets industrial demand.

Key words:  Li-ion batteries, state of charge (SOC), open-circuit voltage method, current integration method