No Leak No Maintenance Lead Acid Battery Separator Safety

1) Lead-Acid Battery Charging Characteristics:
As shown in the figure, during the initial charging phase, the terminal voltage rises rapidly (segments A-B). This is due to the rapid increase in sulfuric acid formed within the plate pores as the lead sulfate on the plates converts to lead and lead dioxide. After reaching point B, the voltage rises gradually and slowly (segments B-C). This is due to the increasing concentration of sulfuric acid within the plate pores and the gradual equilibrium between the rate of outward diffusion. At approximately 90% charge, most of the PbSO₄ on the plate surfaces converts to PbO₂ and Pb. Continued charging leads to significant water decomposition, resulting in a significant accumulation of hydrogen on the negative plate. Hydrogen is a poor conductor, increasing the internal resistance. Simultaneously, oxygen forms a peroxide electrode on the positive plate, raising the positive electrode potential. The increased internal resistance and electrode potential cause the terminal voltage to rise rapidly again (segments C-D). By point D, virtually all of the PbSO₄ on the plate surfaces has converted to PbO₂ and Pb. Gas evolution begins at both battery terminals, indicating "overcharge," and charging should be stopped.

To prevent battery overcharge, the maximum output voltage of automotive alternators is typically limited to 14 ± 0.2V.

Lead-acid battery charging characteristics

2) Constant Current Discharge Characteristics of Lead-Acid Batteries:
As shown in the figure, when the battery begins to discharge, the terminal voltage drops rapidly within a short period of time (segment A-B). This is due to the reaction between the active materials in the plates and sulfuric acid, which reduces the amount of sulfuric acid in the pores and forms a sudden increase in water, causing the electrolyte density within the pores to drop sharply. The voltage then drops more slowly (segment B-C). This is due to the dynamic equilibrium between the water in the pores and the permeation of the higher-density electrolyte outside the plates, which slows the decrease in electrolyte density within the pores. By point C, most of the active materials on the plates have converted to lead sulfate. As the volume of lead sulfate formed on the plate surface and in the pores increases, it becomes difficult for the electrolyte outside the plates to penetrate into the pores, resulting in a rapid drop in the terminal voltage. At point D, the battery voltage drops to approximately 1.75V, and discharge terminates. Beyond point D, the battery is in an "over-discharge" state, and continued discharge will damage the battery.

Lead-acid Battery Discharge Characteristics