Development of a Circuit for a Deterioration Diagnosis of Li-Ion Battery using FFT by FPGA

This paper presents a deterioration diagnosis circuit for Lithium ion (Li-ion) batteries using a Field Programmable Gate Array (FPGA). The terminal voltage of any Li-ion battery rapidly increases at the end of the discharging, and gradually converges to the internal voltage. The internal impedance of the battery can be obtained from the transient characteristics. The internal impedance has a close relationship with deterioration of the battery. The developed circuit diagnoses the deterioration using the frequency characteristics of the internal impedance. The internal impedance is obtained from the frequency responses converted from the transient waveforms in a time domain by Fast Fourier Transform (FFT). The developed circuit allows a quick deterioration diagnosis during operation only by measuring the battery voltage and current. The developed circuit is achieved using common devices and estimates the lifetime of the battery without using expensive measuring equipment.