The capacity of the battery is directly related to whether the car and the tractor can start and operate normally. If the maintenance is not good, even if the new battery is installed, the capacity will drop rapidly and the service life will be shortened. The reasons for the decrease in capacity mainly include the following aspects: 1. Polar plate vulcanization. That is, the white coarse grained lead sulfate gradually formed on the surface of the plate, which is hard and difficult to be dissolved in the electrolyte, and it is not easy to perform a reduction reaction with the electrolyte, thereby reducing the active material. In addition, the coarse-grained lead sulfate blocks the pores of the plate, making it difficult to infiltrate the electrolyte and increase the internal resistance, so that the active material participating in the reaction in the plate is reduced, resulting in a decrease in the capacity of the battery. Causes of plate vulcanization are as follows: (1) The battery is in a state of complete discharge or semi-discharge for a long period of time. Due to temperature changes, such as a high temperature T, a portion of the lead sulfate dissolves in the electrolyte, and when the temperature decreases, it dissolves in the electrolyte. The lead sulfate will re-precipitate and recrystallize to form coarse grains attached to the plates. (2) The liquid level of the battery is lowered so that the upper edge of the battery is exposed to contact with air and oxidation, and then the oxidation part will contact with the electrolyte in the mechanical driving bump to produce coarse-grained lead sulfate, which will cure the upper part of the board. (3) The specific gravity of the electrolyte is too large, the discharge current is too high and the temperature is too high, and the chemical reaction is intensified. The generated lead sulfate is quickly deposited on the plate, and it also promotes vulcanization. In order to prevent the vulcanization of the plates, the battery should always be kept in a fully charged state, the electrolyte should be submerged in the upper plate edge, and the specific gravity of the electrolyte should be properly selected according to the different regions and seasons. ? 2, self-discharge. The fully charged battery is left unused and gradually loses its power, which is called self-discharge. Self-discharge is inevitable. Under normal conditions, the discharge rate per day should not exceed 0.35% to 0.5%. The main reasons for self-discharge: (1) The plate or electrolyte contains impurities. The potential difference between the impurities and the plates or between different impurities creates a localized battery, which forms a loop through the electrolyte and generates a local current to discharge the battery. . (2) The separator cracked, resulting in a short circuit between the positive and negative plates. (3) Electrolyte or water is present on the surface of the battery case and becomes a conductor between the poles, causing the battery to discharge. (4) Exfoliated active material and deposited on the bottom of the battery, causing short-circuit discharge of the plate. In order to reduce self-discharge, besides battery manufacturing materials should be as pure as possible, in the use of the shell surface and pile head must be kept clean, the electrolyte must be filled with chemically pure sulfuric acid and distilled water. 3, the active material off the plate in the normal use of the battery and charge and discharge process, the volume of active material plate is constantly expanding and contracting, will cause the active material to slowly fall off, if used improperly, the active material will quickly fall off a lot of cause Short circuit board. The main reason for the active material shedding on the polar plate is excessive current or temperature during charging, and frequent overcharging. When the discharge, the current is too large (such as access to the starter motor too long), so that the plate is curved (because the plate active material to participate in the degree of chemical reactions are inconsistent, resulting in inconsistent volume changes around the plate), can also cause the active material to fall off . ? 4, shell crack or sealant cracked. Cracks will leak electrolyte and reduce the liquid level. If there are subtle cracks in the internal walls, the two cells communicate and the voltage drops. The main causes of cracks are battery holder screws that are too tight; knocking too fierce; vents blocked, gas can not be released, so that the single grid pressure is too large; winter freezing crack;