In recent years, lead–acid battery applications have experienced a marked evolution. This development has been promoted by the introduction of micro- (start–stop), mild- and full-hybrid vehicles in which recuperation of braking energy, together with electric boosting during periods of acceleration, is provided by the battery. To fulfil both tasks, batteries with enhanced electrical characteristics are required. In particular, it is necessary to increase as much as possible: (i) the ability to accommodate the strong increase in the number of cranking events after each vehicle stop, and (ii) the battery charge-acceptance, so as to maximize the recovery of braking energy and thereby decrease fuel consumption and CO2 emissions. Finally, as the battery operates at a partial state-of-charge, it is imperative to overcome the deleterious effects provoked by high levels of sulfation in the plates ― principally in the negatives ― that otherwise would limit the battery life. Essentially, the negative plate is responsible for the sulfation problem. Without proper additives, the electrical performance of negative plates is limited by the development of an inner structure composed of numerous lead sulfate crystals of large size. This situation is promoted on discharge by acid limitation, and on charge by a high overpotential that restricts charge-acceptance. Numerous studies have demonstrated the outstanding characteristics of organic expanders and especially of carbon and graphite mixtures for controlling the adverse negative-plate behaviour that is exhibited in hybrid vehicle service. The use of special carbon and types of graphite has increased charge-acceptance and battery life. The presentation will describe the progress being made by Atomized Products Group (APG) in the quest for improved expander mixtures, together with new ways of delivering these mixtures, e.g., as pre-blended and completely-mixed expanders, for application in standard and more advanced lead–acid batteries.
APG (Atomized Products Group)
Melchor Fernández holds an MS DC in chemistry. He joined the Technical Department of EXIDE in 1973 where he conducted studies on active materials and corrosion, as well as on battery electrical testing. Melchor was involved with the development of the ORBITAL valve-regulated battery. During the past six years, he has been engaged in the development of EFB and VRLA batteries for mild-hybrids.