A novel comprehensive evaluation method for state-of-health of lead-acid batteries

Abstract

Valve-regulated batteries(VRLA) have been widely applied as backup power supply to ensure the uninterrupted operation of systems in various fields, such as power system, communication system, railway system, banking business and national military defense. Because the application environment of VRLA is complicated, many factors will influence their service lives, for example, charging and discharging current rate, depth of discharge, temperature, etc. The existing estimation methods usually regard the total battery capacity as a fixed value, which results in the estimation error accumulated with the change of charging and discharging current rate. In charge and discharge conditions, the battery capacity is calculated accurately by means of an improved Amper–Hour (AH) method, which has been put forward by us. The influence of discharge rate, charging efficiency, and temperature on the remaining capacity of the lead-acid battery is considered. Therefore, the state-of-charge (SOC) of battery can be quantitatively evaluated and estimated. A real-time dynamic modeling method is proposed to calculate the relationship between the remaining capacity of battery and the internal resistance of battery. The SOC of battery is determined quantitatively by means of measuring the internal resistance of battery accurately. The evaluation system will update the relationship between the internal resistance of the lead-acid battery and the remaining capacity during routine processes of charging and discharging, thereby further improving the system’s accuracy in estimating the remaining capacity of VRLA. An experimental comprehensive evaluation system was built to perform real-time detection and estimation of the SOC of lead-acid batteries.