Dynamic Frequency and Duty Cycle Control Method for Fast Pulse-Charging of Lithium Battery Based on Polarization Curve

Pulse-based charging method for battery cells has been recognized as a fast and efficient way to overcome the shortcoming of slow charging time in distributed battery cells. The pulse frequency for controlling the battery charge will change within a certain range. The optimal frequency is determined to achieve the minimized battery impedance. The adaptation of a duty cycle of the pulse by decreasing the concentrated polarization guarantees a safe charging operation of all the distributed cells within a temperature range of 5 degrees C to 45 degrees C. The proposed charging process can be completed to about 80% of its maximum capacity in less than 20 minutes without damaging the battery characteristics. The newly designed charging results show that about two times faster than the conventional constant-current constant-voltage (CC-CV) charging method and 52% more efficient than the constant current fast charging method. The implemented high fidelity electrical model provides an approach looking into the effect of the pulse on the internal electrochemical reaction process. In addition, cell terminal voltage and temperature are simultaneously monitored in real time so as to adjust the frequency and duty of the proposed charging pulse method preventing battery degradation.