Photovoltaic storage battery, due to long-term use, the positive plate gate will gradually corrode under the action of the electrolyte, and the length of the grid is reduced by the binding property of the living material and the grid, resulting in a gradual loss of the battery capacity. The corrosion of this positive plate gate and the majority of the mainly maintained alloy of the grid, the electrolyte density, and the shape of the ribbed rib shape.(1) Positive electrode active substance softening
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The VRLA battery is in the case of cycle conditions, and the failure of the battery is mainly from the softening of the positive electrode active material (PAM), from falling off.
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During the lead-acid battery cycle, the positive and negative electrode active substances have undergone reversible dissolution reselling processes, and the structure of the porous neutral electrode is changed. Especially for the lead electrode of the neutralization, it may cause an apparent volume, change the distribution of particles and pore size, and the mechanical bonding performance and conductivity between the particles in the porous neutralized cell structure are reduced, and this kind of continuation of the circulation The situation will further deteriorate, as a result, the active material of the region softens and falls off.
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(2) Influence of discharge current on battery life
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In the photovoltaic system, the discharge current of the battery is very small. PBSO4 formed under small current conditions is more difficult to transform the PBSO4 formed under large current conditions. This is because the PBSO4 crystalline particles formed under small current conditions are coarsely larger than the PBSO4 crystalline particles formed under large current conditions, and the coarse PBSO4 crystalline particles reduce the effective area of PBSO4, so that the polarization is accelerated at the time of charge. It leads to difficulty in conversion of PBSO4, as the cycle continues, this situation will more intensify, and the result makes the plates uncharged, resulting in the end of the battery life.
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(3) Recovery of battery capacity after depth discharge
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In a photovoltaic system, the battery's discharge rate is low in other occasions than the battery application, usually in C20 to C240, or even lower. Small current depth discharge means that the active substance on the plate will be more fully utilized. In many photovoltaic systems, depth discharge is usually not discharged, unless the charging system has failed or lasts long-term bad weather. In this case, if the battery is less than timely recharge, the problem of vulcanization will be more severe, and the capacity loss is further caused.
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(4) Effect of acid moral layers on battery life
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The electrolyte layered phenomenon is due to gravity acting during the charge and discharge process of the battery, that is, the positive and negative plate surface produces H2SO4 when charging, its density, and sinking due to gravity. At the time of discharge, the surface of the positive and negative plate consumes H2SO4, so the surface liquid layer density is small, the low density of the electrolytic fluid is launched, and the upper high density of the polar group is downward, electrolysis The result of liquid flow caused a low density and high lower density. The production of hierarchical phenomena has adversely affects the service life and capacity of the battery, accelerates the corrosion of the grid and the falling of the positive electrode active substance, resulting in a negative electrode plate sulfate.
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(5) Effect of electro-hydraulic density on the life of lead storage battery
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The concentration of the electrolyte is not only related to the capacity of the battery, but also related to the corrosion of the positive electrode plate and the negative electrode active substance sulfate. Excessive sulfuric acid concentration accelerates corrosion of the positive plate and negative electrode active material sulfate, and leads to excessive water.
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(6) Influence of the grid alloy
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VRLA battery, due to long-term use, the positive plate gate is gradually corroded under the action of the electrolyte and greater, the length of the grid is reduced by the binding property of the living material and the grid, resulting in a gradual loss of the battery capacity. The corrosion of this positive plate gate and the majority of the mainly maintained alloy of the grid, the electrolyte density, and the shape of the ribbed rib shape.
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During the battery charging process, a non-conductive layer is formed on the interface of the grating and the active material, which causes a high impedance in the grid gate and the PAM interface, resulting in charge and discharge, heat and grid near the grid. PAM Expand, thereby limiting the capacity of the battery (ie, a so-called PCL effect).
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(7) Effect of thickness of polar plates
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The thickness of the polar plate should belong to the problem of battery design. In general, the cycle life of the thick plate is longer than the thinner plate, while the active material utilization is worse than. However, it is conducive to the prolonging of circulating cycle life.
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(8) Shadow of assembly pressure
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The assembly pressure has a great influence on the life of VRLA battery. When the AGM partition is elastic, when assembled, the polar group is not pressurized or the pressure is too small, the partition and polar plates cannot maintain good contact, and the battery capacity is greatly reduced.
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During the circulation process, the expansion, looseness of the active material is one of the reasons for the end of battery life, and high assembly pressure can prevent expansion of the active substance during deep cycle. If the installation pressure is too low, it will also cause the separator to be separated from the plates early, causing electro-hydraulic transmission difficult, and the battery internal resistance increases, which is easy to cause the battery life to terminate. Therefore, the high assembly pressure is a guarantee for the battery having a long cycle life.
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(9) Effect of temperature
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High temperatures are in an accelerated action on the battery of the battery, the heat loss, the positive plate gate corrosion and deformation, etc. When discharging at a certain ambient temperature range, the use capacity increases with the temperature rise, decreases with the temperature. In the range of 10 ~ 45 ° C, the capacity of lead storage battery increases with temperature, such as the valve controlled lead battery at 40 ° C, which is about 10% lower than the power discharge at 25 ° C, but it exceeds certain The temperature range is reversed, as discharged under conditions of 45 to 50 ° C in ambient temperature, the battery capacity is significantly reduced. Low temperature<5℃)时，电池容量随温度降低而减小，电解液温度降低时，其粘度增大，离子运动受到较大阻力，扩散能力降低;在低温下电解液的电阻也增大，电化学的反应阻力增加，结果导致蓄电池容量下降。其次低温还会导致负极活性物质利用率下降，影响蓄电池容量，如电池在-10℃环境温度环境温度下放电时，负极板容量仅达35%额定容量。
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Normally, if it is used under 25 ° C, the battery life is 3 years, then in the case of 30 ° C, it fell to 2.5 years; 40 ° C fell to 1.5 years. That is, at 25 ° C, each liter is 10 ° C, and the life is shortened by half.
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Four. Design practice of energy storage VRLA battery with photovoltaic system
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According to the operating conditions of the photovoltaic system, the above-mentioned factors affecting the battery life are combined, and a series of research and technological improvements have been developed based on the original VRLA battery, and the design and development of photovoltaic systems. VRLA Battery. Specific improvement measures include the following aspects:
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(1) Plate grid alloy: It is suitable for the use of lead-to-ceiling or lead cadmium sheet alloy alloys, which can prevent the electrode from corrosion during use, and can *** grid and active material. To eliminate early capacity attenuation. Its recovery performance after charging efficiency and deep discharge is ideal. Since cadmium is toxic elements, it is now limited. However, due to the leadless alloy battery, it is seriously lost, and now, it is generally made of an open storage battery to make regular hydration, and people need to maintain regular maintenance.
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(2) Plate grid structure: The special grid structure can be prevented from being damaged due to the growth of the grid, and the thickness of the grid is increased to extend the battery life of the battery. The commonly used tubular positive plate grid is now designed, limited to problems that are incoming contact between activity and grids.
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(3) Lead cream: In positive, negative lead paste, add a conductive additive, such as graphite, acetylene black, etc., and improve the cream process and curing process, improve the charging acceptance capacity of the battery, after the discharge capacity Restore capacity and deep cycle life.
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(4) Assembly pressure: Improve the assembly pressure of the battery to improve the battery life of the battery. High-strength tight fitting technology is used to ensure that the battery is in charge.
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(5) Electrolyte: Reduces the specific gravity of the electrolyte of the sulfuric acid, and add special electro-hydraulic additives to reduce the corrosion of the plate, reduce the generation of electro-hydraulic layers, improve the charging acceptance ability of the battery, and over discharge performance.
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(6) Control of impurities: Strict control over impurities of various materials (such as SB, Fe, Ni, etc.), especially the control of impurities in alloy, reduce the self-discharge of the battery, and eliminate the occurrence of negative electrode bus corrosion .
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(7) Comparison of positive and negative active substances: For the charging and discharging characteristics of the energy storage VRLA battery, the photovoltaic system is adjusted, and the ratio of the positive and negative active substance is adjusted, and the cycle life of the battery is increased.
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(8) Safety Valve: The impact of the plateau climate above 2500m or more of the safety valve is also considered, and the opening and closing valve pressure is adjusted, and the special safety valve is adjusted.
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(9) Battery structure: Reduce the overall battery. It is produced with short-type structures, which can greatly reduce the useful life and capacity of the battery due to electro-hydraulic hierarchical phenomena. However, since the colloidal battery is not prone to electrolyte layers, there is no such limit.
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(10) Consistency of the battery of the battery: The consistency mentioned here is not only the open circuit voltage, initial capacity of the battery, but also includes internal resistance, self-discharge, and charging efficiency, etc., which requires sufficient manufacturing. Precision, that is, from the lead powder, casting piece, and paste, smear, curing, chemical, dry assembly, adding acid, and charging to the final four functional tests must be controlled within a smaller tolerance, so it is cast, Machine coating, component assembly, and precise acid are reliable guarantees for ensuring battery consistency, minimizing human factors.
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Summarize
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Since the photovoltaic power generation system is low, high cost, high, and no legal regulations without corresponding supporting, make the photovoltaic system development slower. However, developing new energy is a general trend, and it will have to develop rapidly. The energy storage battery currently includes cadmium-nickel battery and lead-acid batteries, of which cadmium nickel batteries are gradually eliminated. Lead-acid batteries include rich liquid-rich and lean liquids, which will be applicable to the photovoltaic power generation system in recent years.
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