EFFECTS OF RESIDUAL ELEMENTS IN LEAD-ACID BATTERIES

The "maintenance free" Lead-Acid Battery (LAB) system has been developed through the technology of Valve-Regulated Lead-Acid (VRLA) batteries. However, a remarkable issue was revealed by this type of battery: the water consumption [ 1]. This process is caused by secondary reactions that occur during charging or even by the self-discharge: the Hydrogen Evolution Reaction (HER) and Oxygen Evolution Reaction (OER) [2]. The damaging effect due to OER could be reduced since the oxygen produced by the positive plate goes through the separator to the negative plate where is reduced back to water. This process is called "internal oxygen cycle" [3]. The previous reactions are influenced by the presence of metallic impurities in the battery, since, these processes are catalyzed by them [4]. Thus, the negative effects caused by the secondary reactions, as the decrease of high-temperature durability and the increase of self-discharge, could be increased. Due to this fact, the impurity influence on HER and OER was researched in two different experimental systems (three electrode cell and 2 V/ 1 Ah cell). The investigated impurities were nickel, silver and selenium, and their effect was measured at different concentrations. Lastly, the search of similar trends between the results of the two experimental systems and the determination of a HER rate were established as the aims of this study.