In lead-acid batteries, changes in the density of the sulfuric acid electrolyte directly affect the discharge capacity. If the density is too low, not only the density of the electrolyte in the plate hole will drop too much, resulting in the increase of the electrode and the decrease of the capacity, but also the difficulty of diffusion of the electrolyte near the electrode, resulting in a decrease in capacity. Although low density

    A high electrolyte will have an adverse effect on the battery capacity, but the density of the electrolyte should not be too high. If the density of the electrolyte exceeds a certain limit, the inherent resistance of the electrolyte will increase. Viscosity becomes larger. At the same time, the self-discharge of the battery also increases. On the contrary, it is not good for the battery capacity. When the relative density of the electrolyte is 1.22, the conductivity shows a maximum value, but during the battery discharge process, the density of the acid changes, due to the different discharge rates and the temperature corresponding to the inside of the battery

    The optimum density of the electrolyte is also different depending on the amount of the active material and the amount of the electrolyte. Sulfuric acid with a relative density above 1.300, in addition to increasing self-discharge, will also accelerate the corrosion of separators and positive grids in batteries. What needs to be emphasized here is that the increase in the density of the battery electrolyte is only beneficial to the positive electrode, but it is different for the negative electrode. This difference is more significant especially when the battery is discharged at a high current and low temperature. At this time, the negative electrode may become a factor that limits the battery capacity.