Failure modes of battery valve-controlled gel batteries

　　1. Dry failure mode

　　 The discharge of hydrogen, oxygen, water vapor, and acid mist from valve-regulated lead-acid batteries are all methods of battery loss and drying. the reason. The element that dryness constitutes battery failure is unique to valve-regulated lead-acid batteries. There are four reasons for the loss of water: ①The power of gas recombination is low; ②Water seeps from the battery shell; ③The grid corrosion consumes water; ④The self-discharge loses water.

　　(1) Gas recombination power

　　 The gas recombination power is closely related to the selected float charge pressure. If the voltage is selected too low, although the oxygen separation is small and the composite power is high, a single battery will fail due to the lack of salt formation of the negative electrode due to long-term charging, which will shorten the battery life. The float charge voltage is selected too high, the gas separation amount is added, and the gas recombination power is low. Although the failure of the negative electrode is avoided, the safety valve is frequently opened, water loss is large, and the positive grid is also corroded. Affect battery life.

　　(2) Water soaked from the shell data

The related functions of various battery shell materials are shown in the table below. It can be seen from the data in the table that the water vapor penetration rate of ABS materials is relatively large, but the strength is good. The penetration rate of the battery casing depends on the type and nature of the casing material, as well as its wall thickness and the water vapor pressure difference between the inside and outside of the casing.

　　 performance

　　 material value water vapor relative permeability (%) Relative oxygen permeability (%) Mechanical strength

　　Tensile strength

　　 (Mpa) Notched impact strength ( KJ·m-2)

　　ABS16.60.3521~636.0~53

　　PP1.00130~402.2~6.4

　　PVC4.224.4135~5522~108

　　(3) Grid corrosion

　　 Grid corrosion will also cause water consumption. The reaction is:

　　Pb+2H2O → PbO2+4H++4e-

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　　(4) Self-discharge

　　 The oxygen separated from the positive electrode self-discharge can be recombined at the negative electrode without losing water, but the hydrogen separated from the negative electrode cannot In the positive electrode recombination, it will accumulate in the battery, drain from the safety valve and lose water, especially when the battery is stored at a higher temperature, the self-discharge will accelerate.

　　Second, the failure form of premature loss of capacity

　　 Low antimony or no antimony is used in valve-regulated lead-acid batteries. For antimony grid alloys, abnormal early capacity loss is likely to occur under the following conditions:

　　①Unsuitable cycle conditions, such as successive high-rate discharge, deep discharge, and low charge at the beginning Current density;

　　②lack of special additives such as Sb, Sn, H3PO4;

　　③higher during low-rate discharge Active material utilization rate, excessive electrolyte height, electrode plate is too thin, etc.;

　　④The apparent density of the active material is too low, and the installation pressure is one level too low.

　　 Third, the failure form of thermal runaway

　　 Most battery systems have heating problems. In valve-regulated lead-acid batteries This is because the oxygen recombination process causes more heat to be generated in the battery; the amount of gas discharged is small, which reduces heat loss;

　　若The operating environment temperature of VRLA batteries is too high, or the voltage of the charging equipment is out of control, the battery charge will be added too fast, the internal temperature of the battery will increase, the battery heat dissipation is insufficient, and then overheating occurs, the internal resistance of the battery drops, and the charging current goes further As it rises, the internal resistance is further reduced. This repeats a vicious circle until the thermal runaway causes severe deformation and cracking of the battery casing. In order to prevent the occurrence of thermal runaway, corresponding measures should be adopted:

　　①Charging equipment should have temperature compensation or current limiting;

　　②Strictly control the quality of the safety valve so that the gas inside the battery can be discharged normally;

　　③The battery should be set in a well-ventilated position and the battery temperature should be controlled.

　　Four. Irreversible sulfation of the negative electrode

　　 Under normal conditions, lead-acid batteries form lead sulfate crystals during discharge. It can be easily reduced to lead during charging. If the battery is improperly used and protected, for example, it is often lack of charging or over-discharge, the negative electrode will gradually form a kind of thick and strong lead sulfate, which is almost insoluble, and it is difficult to convert it into active materials by conventional charging methods, and then reduce This phenomenon is called the irreversible sulfation of the electrode plate because of the loss of battery capacity and even the stop of battery life.

　　 In order to avoid irreversible sulfation of the negative electrode, it is necessary to charge the battery in time and not over-discharge. Contact: 18038382979