Research On Internal Resistance Measurement For Health Diagnosis Of The Lead-acid Battery

In recent years, the World automobile inventory climbed largely. As people being increasingly concerned on the environment and energy problems caused by the automobile emission, people paid more and more attention to it. The future car must be improved efficiency and reduced pollution. Therefore electric cars are the inevitable trend of modern automotive development. At this stage, although electric vehicle is developing rapidly, the power issue has been the constraints on their development as a major obstacle. The Battery as a kind of clean power is promoted by the industry in which one of the key issues to solve is the health monitoring of the battery. The battery on-line monitoring technology is one of the key technologies of electric vehicle, which not only helps to improve the effectiveness of the battery power, but also helps to improve the safety of battery power. In the paper, the internal resistance has been studied, which is closely related to state of health of lead-acid battery, and it is to design a detection system.This paper describes research progress and methods of the battery health monitoring at home and abroad, analyzes and summaries the advantages and disadvantages of these methods. We find that there is a stronger internal relation between the internal resistance of the battery and the battery health. On this basis, with detailed analysing on battery impedance spectroscopy, it is present a method of the lead-acid battery internal resistance measurement that based on AC impedance method. Both precision resistance and the battery internal resistance constitute a series circuit, by inject a weak sine wave signal into the battery, according to the spectral characteristics of the low-frequency AC signal in the internal battery. The ohm resistor in internal resistance of the battery is equal to its resistance resistance, which, according to Ohm's law in series circuits, is to measure the resistance of a battery and complete the estimation of the health status of the battery. As the AC signal amplitude which is injected into the battery is small (usually in the millivolt level), this paper adopted a series of measures to achieve the signal measurements, including processed the output response by filtering, the peak detection, amplification, AD convert, then the battery internal resistance should be calculated by the voltage. To validate the proposed method, the battery resistance measurement system based on the C8051F040 MCU is designed. Make 20Hz sinusoidal AC signal as excitation source, by means of measure the response signal of battery resistance and precision resistance such that calculates the battery internal resistance. The experimental results show that the proposed method can be effectively used for measuring the internal resistance of lead-acid batteries, and the results of measurement are robust and effective.