An electrochemical technique for state of charge (SOC) probing of positive lead–acid battery plates

Electrochemical experiments that intend to characterise the state of charge (SOC) of lead–acid battery positive plates are presented. These experiments are designed for potential battery plate production quality control and in situ monitoring of battery condition. A small size probe, consisting of a counter and a reference electrode encased in a glass body ending to a fine aperture tip and pressed onto the specimen, was used to apply cathodic galvanostatic pulses on positive plate battery samples. Although this probe arrangement is similar to that of a coulometric thickness gauge, the porous nature of the battery plate results eventually in full discharge of the entire specimen. However, during the initial stages of specimen discharge using the contact probe, a potential arrest was observed for fully charged and partially discharged samples and it was attributed to the time needed for the thickness of a PbSO4 film formed during discharge and the corresponding resistance under the probe’s tip to reach a critical value for the discharge to spread to the rest of the sample. The duration of this potential arrest was found to be related to the positive plate’s SOC indicating the possibility of using the technique in positive plate quality control or in situ monitoring.