Modelling and simulation of lead-acid battery charging

The renewed interest by the US Army in lead-acid SLI battery charging was spurred by the recent shift to Army-wide use of ‘maintenance freeʹ batteries. Although the use of calcium-grid construction reduces the need for periodic water additions, using battery maintainers for extended float charging may cause an even greater problem. By charging at constant voltage, the batteries can slowly lose water if the charging is performed in the absence of suitable temperature compensation. This uncontrolled water loss is of particular significance in those batteries that do not permit access to the electrolyte. In this study, charging curves measured at constant current were obtained over a range of temperatures. The curves were modelled analytically by combining the individual effects of battery charging and gassing. The modelled results were compared with the actual measurements. The model is given as a semi-empirical equation in closed form. With this equation, the response surface is displayed graphically to visualize the effect of changes in critical variables. The results of the investigation will help determine the best charging conditions for the regular and float charging modes in order to deliver the maximum charge without excessive gassing.