Failure modes of lead-acid batteries

Due to differences in the types of plates, manufacturing conditions, and methods of use, the causes of battery failures are different. To sum up, the failure of lead-acid batteries has the following situations: 1. Corrosion variants of the positive plate There are currently three types of alloys used in processing: the traditional lead-antimony alloy, the content of antimony is 4% to 7% by mass; Low antimony or ultra-low antimony alloy, the content of antimony is 2% by mass or less than 1% by mass, containing tin, copper, cadmium, sulfur and other modified crystal agents; lead-calcium series, actually lead-calcium-tin-aluminum The content of calcium is 0.06%～0.1% by mass. The positive grids cast by the above alloys will be oxidized into lead sulfate and lead dioxide during the battery charging process, and finally lead to the loss of the use of supporting active materials and the battery failure; or the formation of lead dioxide corrosion layer makes lead The stress of the alloy causes the grid to grow and deform. When this deformation exceeds 4%, the entire electrode plate will be destroyed, and the active material will fall off due to poor contact with the grid, or short-circuit at the bus bar. 2. The active material on the positive plate falls off and softens. In addition to the active material falling off due to the growth of the grid, as the charge and discharge are repeated, the bond between the lead dioxide particles also relaxes, softens, and falls off the grid. A series of factors, such as the manufacture of the grid, the tightness of the assembly, and the charging and discharging conditions, all have an impact on the softening and shedding of the active material of the positive plate. 3. When the irreversible sulfation battery is over-discharged and stored in the discharged state for a long time, its negative electrode will form a coarse lead sulfate crystal that is difficult to accept charging. This phenomenon is called irreversible sulfation. Slight irreversible sulfation can still be recovered by some methods. In severe cases, the electrode will fail and cannot be charged. 4. Premature loss of capacity. When low antimony or lead-calcium is grid alloy, there will be a sudden decrease in capacity in the initial stage of battery use (about 20 cycles), causing the battery to fail. 5. Severe accumulation of antimony on the active material The antimony on the positive grid is partially transferred to the surface of the active material on the negative plate along with the cycle. The overpotential of the reduction of H+ on antimony is about 200mV lower than that on lead. As a result, the charging voltage decreases when antimony accumulates, and most of the current is used for water analysis, and the battery fails to charge normally. The antimony content of the negative electrode active material of the lead-acid battery whose charging voltage was only 2.30V failed was tested, and it was found that the antimony content of the current negative electrode active material reached 0.12% to 0.19% by mass. For some batteries, such as submarine batteries, there are certain restrictions on the hydrogen evolution of the battery. Once tested on the battery negative electrode active material whose hydrogen evolution exceeded the standard, the uniform antimony content reached 0.4% by mass. 6. Thermal failure. Regarding low-maintenance batteries, it is required that the charging voltage does not exceed 2.4V per cell. In actual use, for example, in a car, the voltage regulating device may be out of control, the charging voltage is too high, and the charging current is too large. The heat that appears will increase the temperature of the battery electrolyte and cause the internal resistance of the battery to decrease; the internal resistance decreases again. Enhanced charging current. The temperature rise of the battery and the excessive current increase each other, and eventually become uncontrollable, causing the battery to deform, crack and fail. Although thermal runaway is not a failure mode that often occurs with lead-acid batteries, it is not uncommon. Pay attention to the phenomenon of excessive charging voltage and battery heating during use. 7. Corrosion of the negative busbar Under normal circumstances, the negative grid and busbar do not have corrosion problems, but in valve-regulated sealed batteries, when oxygen circulation is established, the upper space of the battery is basically overflowing with oxygen, so how much busbars are The electrolyte in the diaphragm climbs up the tabs to the bus bar. The alloy of the busbar will be oxidized to further form lead sulfate. If the busbar electrode alloy is not properly selected, the busbar will have slag inclusions and crevices, and the corrosion will deepen along these gaps, causing the tabs to separate from the busbar and the negative plate to fail. 8. Diaphragm perforation causes a short circuit. Some types of diaphragms, such as PP (polypropylene) diaphragms, have larger pore diameters, and the PP fuse will be displaced during use, resulting in large pores, and active materials can pass through during charging and discharging. Large holes cause micro short circuits and make the battery fail. Disclaimer: Some pictures and content of the articles published on this site are from the Internet. If there is any infringement, please contact to delete. Previous article: Where is the 18650 lithium battery pack?