Capacity estimating method of lead-acid battery by short-time discharge-introduction of approximate expression of discharge curve obtained by compound expression of straight line and hyperbola

In the monitoring technique of valve-regulated Pb-acid (VRLA) batteries, capacity estimation is an important theme as well as prediction of remaining life. This report describes a technique for predicting the overall discharge curve from the initial characteristics of the discharge curve and estimate the duration of discharge. The approximate expression of the discharge curve obtained by the compound expression of a straight line and hyperbola introduced in this report is able to be applied to any battery discharge curve which has deteriorated in various modes such as grid corrosion, dry-out, and sulfation. Estimating the whole discharge curve in the course of estimating the capacity allows the user not only to estimate the discharge duration time at the final voltage specified by the battery manufacturer but also to estimate the discharge duration time by setting the optional final voltage in accord with the equipment.