The amount of active substances is the main factor affecting the capacity of lead-acid batteries. After the amount of active substances in a battery is determined, because the amount of sulfuric acid in the electrolyte is usually sufficient, its theoretical capacity is also determined. The effect of capacity is the effect on the utilization rate of active substances. It should be emphasized here that the theoretical capacity of the active material of the positive electrode and the negative electrode is usually different, and in any case, the actual capacity of the battery should be based on the actual capacity of the electrode with the smallest capacity in the battery, which depends on the degree of influence of different discharge conditions on the actual capacity of the positive and negative electrodes.

    In the actual reaction, the amount of active material participating in the reaction has a great relationship with the thickness of the electrode plate.

    Generally speaking, the active material on the surface of the electrode plate can directly react with the electrolytic wave of sulfuric acid, but the active material in the depth of the electrode plate is not. Kong Xie, the active material in the deep layer of the electrode plate cannot be replenished in time by the electrolyte and the reaction is interrupted. As a result, the thicker the electrode plate, the less the utilization of the active material reaction on the deep electrode plate. This is because, under the premise that the total amount of active materials is the same, the thin plate either increases the number of plates or increases the surface area of ​​the unipolar plate. Both approaches are equivalent to expanding the surface area for electrolyte diffusion. Sulfuric acid reduces the thickness of the diffusion. In this case, not only does the diffusion speed increase and the concentration polarization decrease but also the electrochemical polarization decreases due to the increase in the reaction area.

    The phenomenon that accompanied the discharge process is that the terminal voltage of the battery drops slowly, the discharge capacity of the battery increases, and the thick plate is of course the opposite. Of course, the plate should not be too thin, which will not only affect the cycle life of the battery but also the increase in battery passenger capacity will not be too obvious. It is reported that although the plate is thinner, the utilization rate of active material is higher. However, when the thickness of the electrode plate is reduced to less than 2mm, and the thickness of the electrode plate is further reduced, the utilization rate of the active material does not change much. That is to say, under the premise that the total amount of active materials is the same, the advantages of thin plates are mainly reflected in the case of high current discharge.