Battery Internal Resistance Detection Based on AC Injection Method

The internal resistance of a Lithium-ion battery(LIB) is an important parameter to indicate state of health (SOH). However, the battery internal resistance could not be measured directly, and it is also influenced by temperature and current rate. Therefore, how to obtain the internal resistance of the battery quickly and accurately has attracted attention. In this paper, a detection scheme of battery internal resistance is proposed, which measures the internal resistance of LIB through AC injection method .This method calculates the internal resistance value by injecting a small AC signal into the battery and then measuring the corresponding value of the voltage generated at both ends of the battery. Experimental results show that the internal resistance detection device can measure internal resistance in the range of 2 mΩ to 30 mΩ, and the relative error of measurement accuracy is within 5%.