Lead-acid battery failure modes
initial use lead-acid batteries, with the use of time, the discharge capacity increases gradually reaches a maximum; Then, with the increase of discharge cycles, the discharge capacity is reduced. Battery reaches a predetermined useful life, there are certain requirements on the capacity. Traction battery capacity of not less than 80%; For starters batteries should not be less than 70%. Electric Bicycle Battery Standard shall also was 70%. First, the lead-acid battery of the type of failure mode of the plate, the manufacturing conditions, the use of differences, resulting in battery failure different reasons. To sum up, the failure of lead-acid batteries with the following situations: 1, positive plate corrosion variants currently used in the production of alloys there are three types: the traditional lead-antimony alloy, antimony content of 4% to 7% of the mass fraction; Ultra low antimony or antimony alloy, antimony mass fraction of 2% or less than 1% mass fraction, containing tin, copper, cadmium, sulfur and other variants crystal modifier; lead-calcium, the actual Pb – Ca – Sn – Al quaternary alloys, the calcium content of 0.06% to 0.1% mass fraction. The positive electrode plate of the alloy cast grid, the battery charging process will be oxidized to form lead sulfate and lead dioxide, leading to the loss of the role of supporting the active material of the battery failure; or due to corrosion of lead dioxide layer was formed, the lead Alloy stress, deformation of the plate grid grow, this deformation will make the plate more than 4% of the total destruction of the active material and the grid off poor contact, or short-circuit at the bus. 2, the positive plate active material shedding, in addition to grid growth softening active material loss caused and, with the repeated charging and discharging, the binding between the particles of lead dioxide is relaxed, softened, falling down from the grid. Grid manufacturing, assembly and the charge-discharge conditions, the elastic range of factors, all of the positive plate active material softening, loss affected. 3, irreversible sulfation battery discharge and long-term storage in a discharged state, it will form a thick negative, it is difficult to accept the charging lead sulfate crystals, this phenomenon is called irreversible sulfation. Slight irreversible sulfate, still some way to make it recover, serious, the electrode failure, recharged into electricity. 4, premature capacity loss when the low antimony or lead-calcium alloy grid, the battery during the initial period (about 20 cycles) appear the phenomenon of a sudden drop in capacity, so that battery failure. 5, the antimony in the active material to a serious accumulation of positive grid the antimony with circulation, in part transferred to the negative plate active material surface, the H + antimony on the reduction ratio of lead to restore overpotential lower by about 200mV, So when the charging voltage is reduced accumulation of antimony, most of the current are used for water decomposition, the battery can not charge properly and therefore invalid. The charging voltage is only 2.30V and failure lead-acid battery negative electrode active material antimony conducted laboratory tests found that the surface of the negative electrode active material layer of antimony content of 0.12% to 0.19% mass fraction. Some batteries, such as submarine batteries, hydrogen battery good for certain restrictions. Had more than the standard hydrogen electrode active material for battery testing, the average content of 0.4% antimony mass fraction. 6, thermal failure for low maintenance batteries require charging voltage does not exceed the single-cell 2.4V. In actual use, for example, in the car, may be out of control regulating device, the charging voltage is too high, and thus the charge current is too large, the heat generated will allow battery electrolyte temperature, resulting in decreased battery internal resistance; resistance decrease and enhance the charge current. Battery temperature and current is too large mutually reinforcing, and ultimately can not control, so that the battery deformation, cracking and failure. Although not the lead-acid battery thermal runaway failure modes that occur frequently, but not uncommon. Response when using the charging voltage is too high, the battery generates heat attention. potential transformer 7, a negative electrode bus Corrosion is generally the case, the negative electrode grid, and the bus is no corrosion problems, but in VRLA batteries, when establishing the oxygen cycle, the battery is the upper space is substantially filled with oxygen, and how many bus as the electrolyte separator climb to the bus along the very ears. Bus alloy is oxidized further to form lead sulfate, if the bus electrode alloy inappropriate choice of bus slag inclusions and cracks with corrosion along these cracks will deepen, resulting in very ear and bus off the negative plate failure. 8, the diaphragm perforated diaphragm causing a short circuit of individual species, such as PP (polypropylene) separator, large aperture, and in the course of the displacement occurs PP fuse, resulting in a large hole, the active substance can pass through the charge-discharge process large holes caused by micro-short circuit, the battery is dead. Second, the factors affecting the life of lead-acid battery failure of lead-acid battery is the result of many factors, both the inner plate depends on factors such as the composition of the active material. Crystal type, porosity, plate size, and structural grid material, but also on a number of external factors, such as the discharge current density, electrolyte concentration and temperature, depth of discharge, maintenance, storage conditions and time. Here are the main external factors. 1, that the use of depth of discharge depth of discharge discharge to what extent the process stopped. Depth refers to the release of 100% full capacity. Lead-acid battery life is affected by a great influence on the depth of discharge. The focus is on design considerations deep cycle use, recycling or float use shallow. If the light cycle batteries used for deep cycle use, the lead-acid battery will soon fail. Lead dioxide as the positive electrode active material itself, combined with each other is not strong, the discharge is generated when the lead sulfate, lead dioxide back to the charging time and sulfate, lead oxide, lead molar volume ratio is large, the volume expansion of the active material during discharge. If one mole to one mole of lead oxide into lead sulfate, the volume increase of 95%. This repeated contraction and expansion, which makes the interaction between the lead dioxide particles combined with the gradual relaxation, easy to fall off. If one mole of lead dioxide discharge only 20% of the active substance, the contraction, the degree of expansion is greatly reduced, damage becomes slow binding, therefore, the deeper the discharge, the shorter the cycle life. 2, overcharge overcharge a large extent gas precipitation, then subjected to gas positive plate active material impact of such shocks would promote active material loss; addition, positive grid alloys also suffered serious anodizing and corrosion, so the battery overcharge will make application to shorten the period. 3, the temperature of lead-acid battery life extended with increasing temperature. At 10 ℃ ~ 35 ℃ cnc vertical lathe between each increase 1 ℃, an increase of about 5 to 6 cycles, at between 35 ℃ ~ 45 ℃, increased by 1 ℃ extend the life of 25 cycles or more; higher than 50 ℃ due negative sulfide capacity loss and reduced life expectancy. Battery life in a certain temperature range with temperature increase is due to capacity increases with increasing temperature. If the discharge capacity is constant, the discharge time at elevated temperatures reduced depth, solid longevity. 4, the concentration of sulfuric acid density increases, though the positive plate capacity favorable, the battery self-discharge increases, also accelerated corrosion of the grid, but also to promote the loose lead dioxide off, the battery acid is used as the density increases , decreased cycle life. 5, the discharge current density of the current density increases as the discharge, the battery life is reduced, since the high current density and high acid concentrations, cause the loose lead dioxide anode off.