The hidden losses to battery manufacturers when employing standard formation connectors and current working practices
In recent years, formation processes for lead–acid battery formation are becoming increasingly faster. The aim is to raise battery production without requiring more expensive charging equipment and expansion of the formation department area. To achieve the same ampere-hour input, the formation currents have increased sharply. Consequently, to prevent overheating of batteries, many companies have developed enhanced cooling methods that typically involve better flow of cooling water and evaporative chillers. In all cases, however, the connectors used to carry the higher current have remained the same. Over the past five years, Mark Rigby of UK Powertech, a manufacturer of connectors, has noticed a sharp increase in the damage to batteries and the incidence of fires in formation departments. McDonagh, Rigby and Digatron have therefore collaborated with lead–acid battery manufacturers to detect the origin of this problem. A high-resistance layer at the interface between the formation connector and the battery terminal has been identified. This layer always forms on the inner surface of the lead alloy of the connector head but its deleterious behaviour has become exaggerated by the application of higher formation currents. Whilst extra scrap and fire incidents has been noted by battery manufacturers, the wasted energy and possible damage to the active material of the battery from higher temperatures has not been recognised. This presentation details a study of the hidden cost of poor connections and energy losses. The results indicate two major factors: (i) the formation of a high-resistance layer; (ii) the connector design itself. The latter is the inability to ensure a good physical contact of the connector with the battery terminals. The layer has been examined by electrical tests using Digatron equipment, chemical analysis, and both scanning electron and optical microscopy. Simulated formation tests verify the initial results on energy loss. The presentation concludes with an outline of alternative connector designs and workshop practices that can save a substantial decrease in present wastage levels.
Mike McDonagh holds a BSc and PhD in Metallurgy and Materials Science. He has worked in the battery industry since 1977, during which he has been the Chief of R&D as well as the Production Director for leading battery companies. Currently, Mike works as a manufacturing, design and application consultant to the battery industry, and acts as an expert witness in legal cases.