System design of lithium battery internal resistance measurement using LabVIEW

Lithium battery internal resistance is an important reference index to evaluate lithium battery performance. Since the mechanism of lithium battery internal resistance is complex and changeable, it cannot be directly measured in a general way. In this paper, an orthogonal vector phase locked amplifier, which uses the AC injection method and adopts the virtual instrument technology, Labview, as the platform, is developed to alleviate noise influence and phase difference of the traditional analog phase locked amplifier. The experiment results show that the system can achieve real-time and on-line measurement of lithium battery internal resistance with considerable accuracy. The experiment results also indicate that the system can accurately measure the internal resistance at the milliohm level with a high level of confidence.