Dynamic properties of lead acid batteries. I. Initial voltage drop

This paper reports the results of a laboratory experiment conducted on fully charged flooded and valve regulated lead acid (VRLA) cells. In these tests the batteries were discharged directly from a float voltage state. Fast scanning, battery-monitoring equipment was used to observe battery dynamic responses to sudden load applications. This study was done in order to develop an electrical model of batteries, which is capable of describing the behavior of battery voltage during the initial discharge stage. The ultimate goal of the experiments was to assess the possibility of making battery capacity predictions by observing the battery's response to the application of a 30-60 sec load. In addition the authors found it possible to calculate the battery open circuit voltage (OCV) from the float condition. In this work we develop an empirical electrical model of battery behavior. The methods used to obtain the numeric values for various components of the model are presented. Laboratory experimentation was confirmed by field data that allowed the methods to be tested on known good and bad cells. In this work we attempt to lay the groundwork for a method of capacity prediction using only the data available during short discharges.