9V rechargeable battery.Internal resistance of the battery

　　Internal resistance of the battery

　　a. Positive and negative plate resistance

　　At present, the commonly used positive and negative plates of lead-acid batteries are paste type, which are composed of lead-antimony alloy or lead-calcium alloy grid frame and active material. Therefore, the plate resistance is also composed of plate grid resistance and active material resistance. When the grid is in the inner layer of the active substance, no chemical change occurs when it is charged and discharged, so its resistance is the inherent resistance of the grid. The resistance of the active substance changes with the different charging and discharging states of the battery.

　　When the battery is discharged, the active substance of the plate is transformed into lead sulfate (PbSO4), and the greater the lead sulfate content, the greater its resistance. When the battery is charged, lead sulfate is reduced to lead (Pb), and the smaller the lead sulfate content, the smaller the resistance.

　　b. Electrolyte resistance

　　The resistance of the electrolyte varies according to its concentration. Once a certain concentration is selected within the specified concentration range, the electrolyte resistance will vary with the degree of charge and discharge. When the battery is charged, the resistance decreases as the electrolyte concentration increases while the active substance is reduced. When the battery is discharged, the electrolyte concentration decreases and the resistance increases when the active substance of the plate is sulfated.

　　c. Partition resistance

　　The resistance of the separator varies according to its porosity, and the resistance of the new battery tends to be a fixed value, but with the extension of the battery running time, its resistance increases. Because some lead slag and other sediments are on the separator during the operation of the battery, the porosity of the separator decreases and the resistance increases.

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