State of Charge Estimation for Li-Ion Battery Based on an Improved Peukert's Equation with Temperature Correction Factor

Battery state of charge is related with available capacity. Battery available capacity varies with discharge current. Peukert's equation is a good way to estimate available capacity. But the practicability of Peukert's equation for Li-ion battery has to be verified. Especially, available capacity of Li-ion battery is influenced by temperature obviously. In this paper, discharge experiments under different current are undertaken at room temperature 25°C, and the Peukert coefficients n and k are calculated by available capacities and discharge times at the maximum discharge current and the minimum current. The result indicates battery available capacity estimated by Peukert's equation is practical in 25°C. In order to verify the practicability of Peukert's equation for Li-ion battery at low temperatures, these discharge experiments are done at low temperature. The result indicates, at low temperatures, Peukert's equation is practical for Li-ion battery at low current and unpractical in high current. An improved Peukert's equation with Temperature Correction Factor for the Li-ion battery is proposed. The calculated data catch well with experimental data.